4T Score Research Articles

Correlation between the 4T Score, Enzyme-Linked Immunosorbent Assay and Serotonin Release Assay for Diagnosis of Heparin Induced Thrombocytopenia

Correlation between the 4T Score, Enzyme-Linked Immunosorbent Assay and Serotonin Release Assay for Diagnosis of Heparin Induced Thrombocytopenia

A Case for Calculating 4T Scores: Predictive Value in the Diagnosis of Heparin-Induced Thrombocytopenia

A Case for Calculating 4T Scores: Predictive Value in the Diagnosis of Heparin-Induced Thrombocytopenia

Heparin-induced thrombocytopenia: effect of heat inactivation of patient's serum on functional flow cytometric assay results.

Heat inactivation of a patient's sample is not systematically performed in the diagnostics of heparin-induced thrombocytopenia (HIT). Some authors recommend that the patient's sample is heat-inactivated to avoid the effect of thrombin on platelet activation in a functional assay. Others do not find this additional step essential or even advise against it. An enzyme-linked immunosorbent assay (ELISA) and flow cytometry-based functional assay with CD62P as a marker of platelet activation were performed. Forty-seven patients with suspected HIT and three healthy controls were included in the study. Each serum sample was divided into two aliquots: one was heat-inactivated and the other was not. Both aliquots were tested in parallel using the same donor platelets from four randomly selected individuals. We designed an index of platelet activation for both protocols to assess platelet activation in the assay and to compare the results. We observed a higher percentage of platelet activation in heat-inactivated compared to non-heat-inactivated sera. This phenomenon was seen in low and high heparin steps, although it did not occur for all samples. There were discrepant results in seven samples, which tested negative in the non-heat-inactivated protocol and positive in the heat-inactivated protocol. There was no case in which the result of a non-heat-inactivated aliquot was positive and the corresponding heat-inactivated aliquot was negative. Due to the higher percentages of donor platelet activation, all seven non-compliant cases met our current criteria for a positive result. However, those results were probably false-positive based on ELISA optical density value and 4T score. Therefore, in the current settings, heat inactivation of serum is not suitable for our flow cytometric functional assay since it can cause an elevated risk of creating false-positive results.

Comparison of Screening Scores for Heparin- Induced Thrombocytopenia After Cardiopulmonary Bypass

To compare screening scores for heparin-induced thrombocytopenia (HIT) after cardiopulmonary bypass (CPB). Retrospective cohort study. Cardiothoracic surgery units within a large tertiary healthcare facility from September 2010 to January 2020. All adult patients tested for heparin-induced platelet antibody (HIPA) within 2 weeks after surgery requiring CPB. Using data available to providers at the time HIPA were checked, the 4T's Score, a modified 4T's Score, and a score proposed by Lillo-Le Louet (LLL) etal. were calculated. A retrospective chart review was performed for each patient to determine actual presence of HIT, and screening scores were compared for accuracy. Criteria for inclusion were met in 266 patients. Of these, 34 (12.8%) were high likelihood of HIT, 16 (6.0%), additional patients were clinically ambiguous, and 216 (81.2%) were high likelihood of alternative cause for thrombocytopenia. HIPA tests done before postoperative day 5 were not associated with any high-likelihood cases of HIT regardless of preoperative heparin exposure. Although traditional 4T's ≥4, modified 4T's ≥3, and LLL ≥2 had statistically similar sensitivity for predicting HIT, the modified 4T's and LLL had superior specificity (p < 0.001). Appropriate screening for HIT curbed inappropriate HIPA testing, and reduced the need for empirical treatment while awaiting confirmatory test results. Traditional 4T's was statistically inferior to both the LLL score and a modified version of the 4T's to screen for HIT within 2 weeks of CPB.

Testing for Heparin Induced Thrombocytopenia in Hospitalized Patients: In Line with Evidence?

Background: Heparin-induced thrombocytopenia (HIT) is an immune complication of heparin therapy caused by antibodies to complexes of platelet factor 4 (PF4) and heparin. Both clinical probability and laboratory testing are needed for establishing a diagnosis of HIT. The 4Ts clinical scoring system, due to a very high negative predictive value when low, offers a robust means to exclude a diagnosis of HIT. However, these strategies are under-employed in clinical practice and limited evidence indicates a high prevalence of over-testing for HIT.Methods: This retrospective analysis was conducted to identify patients who underwent heparin/PF4 antibody testing over a period of 12 months. The testing was performed using an ELISA-based IgG anti-heparin/PF4 antibody assay and an optical density (OD) of 0.4 was used as a cut-off for a positive value. Electronic medical records were reviewed for 4T score documentation, anti-PF4 results, SRA testing and 4T scores were retrospectively calculated for all the patients. SAS v9.4 (Cary, NC) was used for statistical analysis.Results: A total of 105 patients who underwent anti-PF4 antibody testing were included for analysis. Majority of the patients in our cohort were admitted in an intensive care unit setting (75/105,71.4%). On chart review, only 17 patients (16.2%) were noted to have documentation of 4T score. Based on the retrospectively calculated 4T scores, 60 patients (57.1%) had low pre-test probability, 41 (39%) had intermediate pre-test probability and 4 (3.8%) patients were noted to have high pre-test probability. Anti-PF4/heparin antibodies were positive in 9 patients, of which 5 (55.5%) patients did not undergo concomitant SRA testing. Out of 9, 4 (44.4%) had weakly positive (0.4-1.0 OD units), 2 (21.1%) had strongly positive (1.0-2.0 OD units) and 2 (21.1%) patients had very strongly positive (>2 OD units) anti-PF4 antibody titers. Out of 105 patients, SRA was tested in 11 patients (10.5%) and was noted to be positive in 1 (0.95%). Overall, 2 patients were diagnosed and treated for HIT, out of which the diagnosis was not confirmed with SRA in 1 patient (due to high pre-test probability and very strong anti-PF4 titers). In the remaining patients, sepsis (48, 46.6%) and drug-induced thrombocytopenia (29, 28.2%) emerged as the most common possible causes of thrombocytopenia.Conclusion: Among hospitalized patients, over-testing for HIT is common. Practices to promote 4T score documentation and evidence-based anti-PF4 testing may help prevent unnecessary costs associated with serological testing and costly alternate anticoagulants. To improve overall outcomes, clinicians should also attempt to identify and treat other more likely causes of thrombocytopenia, especially in patients with low pre-test probability for HIT. DisclosuresNo relevant conflicts of interest to declare.

No Diagnostic Utility of Zero Heparin Control Buffer in Serotonin Release Assay: Findings from a Validation Study

Background: Heparin induced thrombocytopenia (HIT) is a rare immune mediated complication that is triggered in a subset of patients temporal to therapeutic heparin exposure. Laboratory testing is based on screening for the presence of serum anti-PF4 antibodies using sensitive solid-phase immunoassays. If antibodies are detected, functional testing to demonstrate the platelet activating properties and heparin dependence of these immune complexes is then performed. Previous studies have reported possible clinical utility in identifying non heparin dependent platelet activating antibodies using a buffer control with zero heparin in the serotonin release functional assay (SRA). These reports suggested a correlation between reactivity in the zero heparin buffer control and pathogenicity of HIT antibodies which may define a subtype of HIT, referred to as autoimmune HIT. We aimed to investigate the utility of zero heparin buffer control as a part of an inhouse validation study of a mass spectrometry-coupled SRA (Mayo-SRA).Methods: Three hundred archived serum samples were tested using anti-PF4 IgG antibody enzyme-linked immunosorbent assay (ELISA; Immucor Diagnostics, GA, USA). SRA was preformed on all samples using Mayo-SRA and reference 14C SRA methods. Zero heparin control buffer was included in the Mayo-SRA assay. Serotonin release >20% in the low dose heparin (0.1U/mL, LDH) and ELISA optical density (OD) >0.4 were considered positive. Drug interference studies were performed by spiking known SRA-positive samples with increasing concentrations of unfractionated heparin (UFH), low molecular weight heparin (LMWH) or fondaparinux in the LDH and zero heparin SRA. The clinical 4T score was calculated retrospectively calculated for all patients.Results: Of the 300 tested samples, 57 were anti-PF4 ELISA positive. 33 of the 57 samples were positive using the reference 14C SRA method. Whereas 43 samples were positive by Mayo-SRA assay. Three additional samples were positive by Mayo-SRA, but negative by both screening anti-PF4 ELISA and the reference SRA method (Fig- 1A). Lastly, 13 samples were anti-PF4 ELISA positive, but SRA negative by both methods in comparison. Interestingly, 44 of 46 (95%) samples interpreted positive by LDH were also interpreted positive (serotonin release >20%) under zero heparin conditions. These included the 3 samples that were positive by Mayo-SRA but negative by both screening anti-PF4 ELISA and the reference SRA. The overall % serotonin release using zero heparin control was significantly lower (P= 0.003, paired Student T-test) compared to LDH (Fig-1B). In addition, zero heparin followed a similar pattern as LDH, with highest levels at ELISA OD units >2 (Fig-1C).Strikingly, drug interference studies showed artifactual serotonin release in the zero heparin reaction, which was not detected in the absence of spiked drugs. For UFH, serotonin release in zero heparin control occurred at very low spiked concentrations, ≥0.063 U/mL. LMWH and fondaparinux spiking experiments also displayed similar zero heparin serotonin release patterns (Fig-1D). Of note, none of these interferences were detected in UFH spiked SRA-negative samples (data not shown).Conclusion: Contrary to prior results suggesting that less than 50% of LDH SRA positive samples are also positive in the zero heparin SRA, our results show high zero heparin SRA positivity rate of >95%. Zero heparin SRA showed a pattern with highest levels at ELISA OD units >2 suggesting that reactivity in this condition is a function of antibody strength rather than a qualitative difference (i.e. “autoimmune” HIT antibodies vs “non-autoimmune” HIT antibodies). In addition, contamination of patient sera with small amounts of remnant heparin can significantly impact platelet activation in the zero heparin SRA test. Thus, zero heparin SRA positive results may be artifactual and represent residual heparin contained in the patient sample.Figure legend:Fig-1A. Scatter plots of SRA positive samples grouped by 4T scores. Red dots are Mayo-SRA only positive samples. Fig-1B and Fig-1C. Scatter plots of % serotonin release of Mayo-SRA positive samples at LDH (circles) vs. zero heparin buffers (squares), and grouped by ELISA OD values, respectively. Fig-1D. % Serotonin release of known SRA-positive samples spiked with increasing concentrations of UFH, LMWH, or fondaparinux at LDH (white) or zero heparin buffers (red). [Display omitted] DisclosuresPruthi: CSL Behring: Honoraria; Genentech: Honoraria; Bayer Healthcare AG: Honoraria; HEMA Biologics: Honoraria; Instrumentation Laboratory: Honoraria; Merck: Honoraria. Padmanabhan: Veralox Therapeutics: Membership on an entity's Board of Directors or advisory committees.

Diagnostic Utility of High Dose Heparin Confirmation Step in Heparin Induced Thrombocytopenia ELISA Assay

Introduction:Heparin-induced thrombocytopenia (HIT) is a potentially life-threatening condition that could occur following exposure to heparin. Accurate and timely diagnosis is critical for appropriate clinical management. Laboratory testing for suspected cases is based on screening for the presence of serum anti-PF4/heparin antibodies using solid-phase enzyme-linked immunosorbent assay (ELSIA) which is known to be sensitive but less specific. A positive ELISA test is followed by functional testing to demonstrate the platelet activating properties and heparin dependence of the pathogenic antibodies. Serotonin release assay (SRA) is considered the gold standard functional test for the diagnosis of HIT. In most anti-PF4/heparin ELISA assays, a high-dose heparin buffer (100U/mL) confirmation step is recommended to demonstrate heparin dependence of detected antibodies and increase the specificity of the assay. The necessity of this confirmation step is controversial with some reports suggesting it could lead to misinterpreting positive ELISA results as negative or indeterminate, especially in cases of very strong and high titer HIT activating antibodies. We hence aimed to investigate the utility of applying this confirmation step as part of an inhouse validation study of a mass spectrometry-coupled SRA (Mayo-SRA).Materials:Three hundred archived serum samples were tested using anti-PF4/heparin IgG antibody ELISA (Immucor Diagnostics, GA, USA). High-dose heparin (100U/mL) confirmation step was performed on all samples with OD units ≥0.4 as recommended by the manufacturer. Samples with OD ≥ 0.4 and ≥50% OD inhibition in the high dose heparin confirmation step are interpreted positive. Mayo-SRA results were compared to a reference 14C SRA method. The 4T clinical score was retrospectively calculated for all patient (range 0-8 points).Results:Of the 300 tested samples, 57 samples were interpreted positive by the anti-PF4/heparin screening ELISA. 33 of the 57 samples were positive using the reference 14C SRA method, whereas 43 samples were positive by Mayo-SRA assay (≥20% serotonin release). Three additional samples were positive by Mayo-SRA, but negative by both screening ELISA and the reference 14C SRA method. All samples with OD units ≥0.4 displayed >50% inhibition in the high-dose heparin regardless of the intensity of the initial OD value or the HIT 4T score, with the exception of one that was negative by both SRA methods and of 1.35 OD value and 6 4T HIT score (Fig-1A). Importantly, thirteen samples were anti-PF4/heparin positive, but SRA negative (by Mayo-SRA and reference method). These samples also displayed positive %heparin inhibition (≥50% OD inhibition) (Fig-1B). Lastly, there were no differences in the degree of %inhibition in samples positive by both reference and Mayo-SRA or Mayo-SRA only (Fig-1B).Conclusion:In our patient cohort, addition of the high dose heparin inhibition confirmation step to the screening anti-PF4/heparin ELISA assay was of no additional diagnostic utility. We hence propose eliminating the heparin inhibition step which would improve laboratory turnaround time, reduce costs, and importantly speed up urgent clinical management decisions.Figure Legend:Fig-1A. No correlation between initial OD values and %OD inhibition using high dose heparin. Scatter plot of all ELISA positive samples (OD ≥0.4) grouped according to OD values. Samples include all SRA-positive and thirteen SRA-negative ELISA-positive samples. Fig-1B. Scatter plot of %OD inhibition comparing samples positive by Mayo-SRA and reference SRA method, positive by Mayo-SRA only, and ELISA-positive SRA-negative by both methods. [Display omitted] DisclosuresPruthi: Bayer Healthcare AG: Honoraria; CSL Behring: Honoraria; Merck: Honoraria; Genentech: Honoraria; HEMA Biologics: Honoraria; Instrumentation Laboratory: Honoraria. Padmanabhan: Veralox Therapeutics: Membership on an entity's Board of Directors or advisory committees.

Spontaneous Heparin-Induced Thrombocytopenia and COVID-19 Infection

Background and Objective: Heparin-induced thrombocytopenia (HIT) can develop if immune responses to infections become pathologic in the presence of heparins. Low molecular weight heparin or unfractionated heparin are recommended for prophylaxis and treatment of venous thromboembolic disease in hospitalized patients with Covid-19 infection but may trigger HIT. Our aim is to alert clinicians that HIT occurs in association with Covid-19 infections even in the absence of prior exposure and may not be easily recognized without a high index of suspicion. Case Summary: A 33-year-old previously healthy male was initially evaluated for low grade fever, dyspnea without hypoxia and cough. A Covid-19 PCR swab was negative despite a recent exposure. He was treated with azithromycin. However, his symptoms did not improve, he then developed right leg swelling and hypoxia, so he was re-evaluated. CTA of the chest showed bilateral pulmonary emboli and ground-glass opacities at the lung bases. Venous Duplex Ultrasound showed non-occlusive thrombus in the deep veins of right lower extremity. He was hospitalized and placed on oxygen and heparin. Covid-19 swab was negative again. Laboratory tests before heparin showed a decreased platelet count of 64,000 k/ul, elevated prothrombin time of 16.4 seconds, normal aPTT at 30.8 seconds, decreased serum fibrinogen at 120 mg/dl and markedly elevated D-dimer at 59,966 ng/ml. Lupus anticoagulant and anti-phospholipid antibody tests were negative. On heparin at the desired therapeutic aPTT target range, the right leg became significantly swollen and painful by day five. Platelet count had decreased further to 39,000 k/ul. Repeat doppler examination of the right leg now showed more severe and extensive deep venous thrombosis. D-dimer had increased to 125,133 ng/ml. The HIT 4T score was 4, suggesting intermediate probability. Rapid HIT immunoassays on 2 separate samples were positive. Heparin was discontinued and he was placed on argatroban. Serotonin release assays on 2 separate samples came back positive. Suspicion for Covid-19 infection remained high and so a Covid-19 serology sample was obtained which was positive for IgG. A repeat nasopharyngeal swab at this time turned positive. He did not receive any COVID specific treatments. As viability of his leg appeared threatened, he underwent right iliofemoral vein thrombectomy with arteriovenous fistula creation. He improved on argatroban and was transitioned to apixaban with gradual normalization of hemostasis laboratory parameters, improvement in hypoxemia and fading clinical symptoms, he was discharged home on day 15. Conclusion: Current consensus guidelines for thromboprophylaxis and treatment of thromboembolism in hospitalized patients with Covid-19 infection recommend heparins as primary therapy to reduce morbidity and mortality. However, our report in addition to the two previous reports of HIT in Covid-19 patients illustrate that HIT can be a complication in the setting of Covid-19 infection. Further, our report also highlights that HIT with thrombosis can occur in a spontaneous manner in the absence of prior heparin exposure, which has been so far studied only in bacterial infection with the hypothesis that Platelet factor 4 (PF4) can bind to negatively charged polysaccharides on the surface of bacteria, triggering an immune response. DisclosuresNo relevant conflicts of interest to declare.

COVID-19 COAGULOPATHY SECONDARY TO ACTIVATING PLATELET ANTIBODIES

TOPIC: Chest Infections TYPE: Medical Student/Resident Case Reports INTRODUCTION: Coagulopathies have been extensively reported in COVID-19 patients (1). CASE PRESENTATION: A 58-year old female presented to the emergency department (ED) with 2-weeks history of shortness of breath. A nasopharyngeal swab was positive for SARS-CoV-2. She was treated and discharged on room air. D-dimer (DD) and platelet (plt) count at the time of discharge were within normal. Six days after discharge she presented to the ED with severe abdominal and right leg pain. Lower extremity pulses were present by doppler but hard to palpate. Laboratory tests showed elevated DD (27,820 ng/ml) and elevated plt (530 x109/L), table-1. Computed tomography scan (fig-1) of the abdomen and pelvis showed multiple wedge-shape infarcts in the liver, spleen, and right kidney and acute thrombosis of the right common iliac artery. Acute deep vein thrombosis in the lower and upper extremities were excluded by US. Duplex US of the right lower extremity showed ankle brachial index of 0.2. The patient was admitted and started on heparin therapy. On day 2, plt count dropped to 127 x 109/L. The 4T score was 5, heparin was stopped and argatroban was started. Serotonin release assay was sent and showed no inhibition with high dose heparin. However, non-heparin dependent anti-platelet activating antibodies (class I HLA antibodies) were detected. Anti-platelet factor-4 was negative and patient was restarted back on heparin. Thrombophilia and autoimmune work up were negative. Patient was discharged on low-molecular weight heparin. Plt count was 179 x109/L before discharge. DISCUSSION: Recent study published by Bilaloglu showed that 533 (16.0%) COVID-19 patients had at least one thrombotic evet during hospitalization. Of all 3334 patients, only 32 (1.0%) had acute limb ischemia, upper extremity arterial thrombosis, renal, and splenic infarcts, and portal vein thrombosis (2). In another case series, 4 of the reported 7 cases developed progressive irreversible lower limb ischemia. Two patients presented with lower limb ischemia and the other two developed severe thrombosis after 4 and 15 days respectively. Of the reported lab values, two patients had D-dimer levels more than 20,000 ng/ml and the same two were thrombocytopenic (1). Interestingly, our patient had reversible limb ischemia as shown by the repeated duplex US done after discharge. Nicolai and colleagues reported that plts hyperactivation and possible immuno-thrombosis may play a role in the pathogenesis of coagulopathy among severe COVID-19 patients (3). In our case, patient had hypercoagulability secondary to activating anti-platelets antibodies, a novel finding that can help understanding the pathogenesis of COVID-19 induced hypercoagulability. CONCLUSIONS: COVID-19 associated coagulopathy can be un-predictable. Activating anti-plt antibodies may play a role in the pathogenesis of COVID-19 coagulopathy. REFERENCE #1: Kashi M, Jacquin A, Dakhil B, et al. Severe arterial thrombosis associated with Covid-19 infection. Thromb Res 2020;192:75-7. REFERENCE #2: Bilaloglu S, Aphinyanaphongs Y, Jones S, Iturrate E, Hochman J, Berger JS. Thrombosis in Hospitalized Patients With COVID-19 in a New York City Health System. JAMA 2020. REFERENCE #3: Nicolai L, Leunig A, Brambs S, et al. Immunothrombotic Dysregulation in COVID-19 Pneumonia is Associated with Respiratory Failure and Coagulopathy. Circulation 2020. DISCLOSURES: No relevant relationships by Bahaa Abdelghaffar, source=Web Response No relevant relationships by hamed daw, source=Web Response No relevant relationships by Tariq Kewan, source=Web Response No relevant relationships by Talha Saleem, source=Web Response

The path of uncovering a prothrombotic thrombocytopenic syndrome after viral vector‐based COVID‐19 vaccination: Where there is much light, the shadow is deep

The path of uncovering a prothrombotic thrombocytopenic syndrome after viral vector‐based COVID‐19 vaccination: Where there is much light, the shadow is deep

Diagnosing heparin-induced thrombocytopenia in mechanical circulatory support device patients

Mechanical circulatory support device (MCSD) patients with positive heparin-induced thrombocytopenia (HIT) screening pose a unique challenge, as clinicians must make rapid decisions about their anticoagulation and whether they can safely undergo cardiopulmonary bypass. We identified screening practices at our institution and other institutions nationwide that differed from American Society of Hematology (ASH) guidelines. This discovery prompted a data review to confirm the applicability of guidelines to this unique population and to highlight complications of "gestalt" screening. Our study included MCSD patients with HIT testing from April 2014 to August 2020. We evaluated 510 PF4 IgG ELISA results. HIT was confirmed in 4.2% of patients. There was an increased prevalence of HIT in patients with nondurable (5.3%) vs durable devices (2.9%) or those in the preimplantation setting (1.3%), however this difference was not statistically significant (p=0.26). None of the patients with a low probability 4T Score had HIT. All patients with a high probability 4T Score and PF4 immunoassay OD >2.0 had HIT. False positive results occurred in 22% of assays ordered for patients with a low probability 4T Score. Twelve patients with a low probability 4T Score and a false positive immunoassay were switched to a direct thrombin inhibitor (DTI) while awaiting confirmatory results. Two patients experienced clinically significant bleeding after conversion to a DTI. An organ was refused in one patient with false positive HIT screening. Our findings demonstrate that an opportunity exists to improve clinical outcomes by re-emphasizing the utility of established guidelines and highlighting their safe use in the MCSD patient population.

Direct Oral Anticoagulants as Successful Treatment of Heparin-Induced Thrombocytopenia: A Parisian Retrospective Case Series.

Background: Heparin-induced thrombocytopenia (HIT) is a prothrombotic life-threatening disorder caused by an adverse reaction to heparin exposure. In this context, it is imperative to stop heparin immediately and to replace it by a non-heparin anticoagulant therapy. Despite their advantages, the use of direct oral anticoagulants (DOACs) is only emerging for HIT treatment, and their use remains rare.Objective: To improve our knowledge on the emerging role of DOACs as treatment of HIT and give an overview of our local practices in this context.Patients/Methods: This is a multi-centric retrospective case series of HIT patients referred to our Parisian pharmacovigilance network and treated with DOACs.Results: We report the cases of seven patients from four healthcare centers, diagnosed with HIT (4T score ≥ 4, positive anti-PF4/heparin immunoassay and positive serotonin-release assay) and treated with DOACs. After a few days on substitutive parenteral treatment (n = 6) or directly at HIT diagnosis (n = 1), these patients were treated with either rivaroxaban (n = 6) or apixaban (n = 1) during acute HIT phase. Mean time to platelet count recovery after heparin discontinuation was 3.3 days (range 3–5). No patient experienced major or clinically relevant non-major bleeding or thrombosis that could be related to DOAC treatment during follow-up.Conclusions: Our cases studies are consistent with recent guidelines credit to the potential and safe use of DOAC during acute HIT in clinically stable patients.

High Levels IPF as Possible Predictor Heparin-Induced Thrombocytopenia

Background: Heparin-Induced Thrombocytopenia (HIT) represents a serious complication of heparin treatment. IgG antibodies binding Platelet Factor 4 (PF4) and heparin trigger the clinical manifestations of HIT. A 4T score is used to stratify the selection of patients suitable for examination. However, the selection of suitable patients remains at the discretion of the clinician, who is confronted with determining the cause of thrombocytopenia. The inclusion of the evaluation of the Immature platelet fraction result seems to be a suitable complement to the stratification of patients because we do not climb elevated IPF values when consuming platelets due to their immunization. Materials and Methods: In a group of 432 thrombocytopenic samples IPF was detected and analyzed in 45 patients with suspected HIT, a 4T score was determined; IPF and HIT functional tests were examined. IPF was determined by oxazine fluorescent dyeing structures of nucleic acid-containing platelets and fluorescence detection on a Sysmex XN 1000 analyser. To determine HIT, impedance aggregometry using the Multiplate® analyser (MEA) as heparin-induced aggregation techniques. The MEA method uses sensitization of donor platelets with patient plasma in the presence of heparin at a concentration of 0.5IU/mL. Results: From the results of the test, it is evident that 10 patients from our group of 45 examined showed positivity of HIT, which is a significant number due to the proven occurrence of HIT in patients treated with LMWH and showing thrombocytopenia. If we evaluate these 10 patients in terms of IPF value, it is evident that 6 of them have an increased value of IPF &gt;10%, which is a 33% positive predictive value and 4 have IPF &gt;30%, when the positive predictive value is even 100%. Conclusions: Diagnosis of HIT remains a complicated clinical laboratory issue. However, new diagnostic options provide considerable potential for solving this problem. The implementation of IPF assays helps us in the diagnosis of HIT on two levels. On the one hand, it provides us with information on platelet consumption in hospitalized patients and thus draws our attention to HIT as one of the options for congestive thrombocytopenia, unless, of course, disseminated intravascular coagulation or thrombotic microangiopathy. Secondly, its implementation will increase the predictive value of the 4T score in patients at medium risk, which is, however, the vast majority indicated for HIT examination.

HIT-It or Quit It: Heparin-Induced Thrombocytopenia Testing Appropriateness Using 4T Scoring and Inappropriate Testing Cost Analysis.

The American Society of Hematology's 4T scoring system is a validated tool to assess a patient's probability of having heparin-induced thrombocytopenia (HIT) before testing is performed. There is no benefit to testing patients with a low probability 4T score for HIT. This study aimed to assess for inappropriate HIT testing at our institution based on 4T scoring. We retrospectively reviewed 201 patient charts and calculated 4T scores and testing costs to assess for inappropriate testing and the economic impact of such testing. HIT testing often occurred in the least appropriate patients and resulted in tens of thousands of dollars of waste for unnecessary testing. Inappropriate testing for HIT is still a prevalent issue despite literature supporting the 4T score for guidance in testing appropriateness.

Heparin‐induced thrombocytopenia in end‐stage renal disease: Reliability of the PF4‐heparin ELISA

BackgroundDiagnosing heparin‐induced thrombocytopenia (HIT) in patients with end‐stage renal disease (ESRD) can be difficult, as they are frequently exposed to heparin and have multiple etiologies for thrombocytopenia. ObjectiveTo correlate 4T scores, IgG heparin–platelet factor 4 (PF4‐heparin) ELISA results, and serotonin release assay (SRA) results in patients with ESRD. MethodsWe performed a retrospective review of patients with ESRD (creatinine clearance < 15 mL/min or on renal replacement therapy [RRT]) who underwent PF4‐heparin ELISA testing from October 2015 to September 2019. True‐positive PF4s required an intermediate to high 4T score (≥4), a positive SRA, and receipt of treatment for a HIT diagnosis. False‐positive PF4s were defined as a positive PF4 with a negative SRA, low 4T score (<4), or lack of treatment for HIT. Indeterminant cases were classified on the basis of clinical assessment by the treating team (eg, hematology or vascular medicine). ResultsOf 254 patients with ESRD (92% on RRT), 29 patients (11.4%) had a positive PF4. Eleven (37.9%) had a confirmed diagnosis of HIT: 10 patients who met all of the above criteria, and one who met the 4T criteria and was treated for HIT but did not have SRA testing due to high clinical suspicion and a positive PF4 test. False‐positive PF4 values occurred in 8 patients (27.5%). Of 10 (34.5%) indeterminant cases of patients with a negative SRA but intermediate to high 4T and positive PF4, only 3 patients were treated for HIT, whereas the other 7 were judged not to have HIT as assessed by the treating clinician. In patients with an intermediate to high 4T score and PF4 optical density > 0.4 but negative SRA, who were not treated for HIT, there were no adverse outcomes documented such as new or progressive thrombosis. ConclusionIn our ESRD population, 4T scores and PF4 testing were not predictive of a clinical diagnosis of HIT.

Heparin-Induced Thrombocytopenia: Are We Ordering Too Much

Introduction:Heparin induced thrombocytopenia (HIT) is a well described cause of IgG antibody mediated platelet consumption.Over-testing for HIT is highly prevalent in the hospital setting. Physicians' fear of missing the diagnosis might contribute to these findings, despite the high negative predictive value of the 4T probability score and the HIT Expert Probability (HEP) score. Also, the initiation of HIT treatment pending confirmatory testing, results in a subsequent increase of costs and exposure of patients to the unnecessary risks of anticoagulation. The aim of our study is to identify clinical and laboratory factors that might affect the decision of testing for HIT in the setting of low or intermediate pretest probability and to prove that this entity is over-investigated and over-treated in the in-hospital environment.Methods:We conducted a cross-sectional retrospective observational study at Hofstra University Northwell Health Staten Island Hospital. Inclusion criteria were patients 18 years and older who had undergone anti-PF4-heparin antibody testing on an inpatient basis, from January 2013 till August 2015. Patients were excluded only if the test was done as outpatient. Statistical analysis was conducted using independent-sample t- test, Chi-square test or Fisher's exact test. All statistical tests were 2-sided and conducted at the 0.05 level of significance. Data was analyzed using the SAS® System Version 9.3 (SAS Institute Inc., Cary, NC).Results:Data was collected on 89 patients who underwent anti-PF4-heparin antibody testing. 84 patients (94%) underwent HIT testing with a low 4T score, as compared to 5 patients (6%) with a high 4T score. There was no significant difference in the proportion of testing with respect to gender, age, the service under which the patient was admitted (medicine vs. surgery), presence of a hematology consult, a history of cardiac surgery, type of heparin used and an elevated Charleson score. 80% (n=74) of patients had another cause for thrombocytopenia and had the HIT panel ordered despite a low/intermediate 4T score (Table 1).In our study, 5 patients tested positive for HIT. 3 of the patients had high 4T and HEP score pretest probability, while 2 of the patients had intermediate 4 T score and high HEP score pretest probability. All 60 patients with a low 4 T score tested negative for HIT (Table 2).After ordering HIT serology, heparin was discontinued in 82 patients. 17 patients with low/intermediate 4T score were started on anticoagulation, 2 of them had new bleeding event. 6 patient with high 4T score were started on anticoagulation, and 1 of them had a bleeding event (Table 3).Conclusion:HIT poses a significant diagnostic challenge. It is an uncommon cause of thrombocytopenia that carries significant morbidity and mortality. Our study showed that HIT testing using ELISA immunoassays is being ordered excessively in the setting of low to intermediate pretest probability leading to unwarranted treatments at significant costs and carrying an important burden on the healthcare system. However, a high number of comorbidities did not seem to lower the threshold for ordering HIT panel. It is very challenging to conduct randomized trials on less common diseases in the clinical setting to improve test ordering practices. The HEP score might be an important adjunct to clinical decision making in the future but this requires more studies being conducted. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Striving to HIT the Bullseye When Diagnosing Heparin-Induced Thrombocytopenia

Background: The 4T score is a validated tool to assess the pretest probability of heparin-induced thrombocytopenia (HIT), with the negative predictive value of a low 4T score (≤ 3) reported consistently above 90%. We performed a retrospective data review of patients aged ≥18 years who had heparin/PF4 antibody testing ordered between January and August 2016 at an academic medical center. 4T scores were calculated retrospectively from data in the electronic medical record (EMR). We then prospectively instituted a mandatory data-driven algorithm utilizing an electronic 4T calculator within the EMR prior to heparin/PF4 antibody testing.Aims: To reevaluate the utilization of laboratory testing for HIT after implementation of a data driven algorithm.Methods: In December 2016, 4T score calculation was implemented in the EMR as a requirement prior to ordering heparin-PF4 antibody testing. We then compared the frequency and results of heparin/PF4 antibody testing in adult inpatients aged ≥18 during the post-intervention period (December 2016 to June 2017) with the pre-intervention period (January to August 2016). 4T scores were calculated retrospectively by a hematologist from data in the EMR and compared to the 4T score entered by the ordering provider.Results: During the pre-intervention period, 161 heparin/PF4 antibody tests were performed, of which 131 (81%) were negative (optical density <0.40), 27 (17%) positive and 3 (2%) equivocal. During the post-intervention period, 105 heparin/PF4 antibody tests were performed, of which 86 (82%) were negative (optical density <0.40), 15 (14%) positive and 4 (4%) equivocal. The 4T score was significantly higher in patients with positive/equivocal heparin/PF4 antibody values compared to those with negative values (p<0.0001). ROC curves demonstrated that the 4T score was highly predictive of a positive or equivocal heparin/PF4 antibody value (AUC 0.705, 95% CI: 0.553, 0.857). Intensive care units ordered the majority (65%) of heparin-PF4 antibodies both pre- and post-intervention. The percentage of heparin-PF4 antibodies ordered with a low 4T score (≤3) was 67% pre-intervention and 57% post-intervention, a difference which trended towards, but did not reach statistical significance (p=0.130 by Chi-square test). 4T score calculation was discordant between the ordering provider and hematologist in 67% of patients.Conclusions: Mandating 4T score calculation prior to heparin/PF4 antibody testing did not significantly decrease the number of tests ordered in the setting of a low 4T score within the first 6 months post-intervention. We plan to review additional data over the next several months and will continue education on accurate 4T score calculation and testing for HIT at our academic medical center. DisclosuresNo relevant conflicts of interest to declare.

Analysis of Patients Mislabeled with Heparin Induced Thrombocytopenia

Introduction: Heparin-induced thrombocytopenia (HIT) is a rare diagnosis, however commonly tested. We hypothesize that the 4T score, a diagnostic tool to diagnose HIT, is underutilized by clinicians. This may subsequently lead to unnecessary testing for HIT, administration of costly alternative anticoagulants, and mislabeling of heparin as allergy. We present preliminary data of our quality improvement study. Our aim was to analyze patients previously labeled with heparin allergy and analyze the 4T's scores, optical density values (OD), and serotonin release assay (SRA) results.Methods: We conducted a retrospective study of patient at two tertiary care hospitals who were evaluated for HIT from October 2015- present. We were notified by pharmacy when a HIT panel was sent and alternative anticoagulation was started. Patients with unknown heparin administration from outside institutions were excluded from the study. We calculated the 4T's score and further categorized low (0-3), intermediate score (4-5), and high (6-8) score. We considered the patients to have “true HIT” if they had 4T's score > 5 or optical density values >0.4 and positive SRA.Results: We analyzed 50 patients who were evaluated for HIT and placed on alternative anticoagulation. We observed that 64% (32/50) of the patients were listed as having heparin allergy secondary to HIT, while 36% (18/50) were not listed to have HIT as allergy on electronic health record. 19 of the 50 (38%) had scored had low 4T's score, of that two tested for HIT with a score of 0 (4%, n=50), 22 (44%) had intermediate, and 9 (18%) had high. When we utilized the 4T's score as pre-test clinical score, 0/13 patients with low score (6 not tested for SRA) and 0 /18 with intermediate score (4 were not tested) had positive SRA. 4 of the 9 (67%) high score were positive (3 were not tested). When we evaluated SRA results for patients with OD value >0.4, we observed 3 with OD value >2 and 1 with OD value of 0.798 had positive SRA. Interestingly, 1 with OD value of 2.136 had negative SRA. 8 patients with OD values > 1 had negative SRA.Conclusion: Preliminary results show that patients are frequently tested for HIT, misdiagnosed with HIT, and mislabeled with HIT in electronic health record. When 4T's is used as clinical score, patients with low probability should not be further tested for HIT. Our study has different results for compared to study of Lo GK et al who utilized 4T's score as pre-test clinical score. 1According to the study patients with low score had <5% of probability of HIT and intermediate score had 8%-29% probability of HIT. However, based on our preliminary data, none of the patients with low and intermediate score had true HIT when SRA was tested. With the intent to practice cost-effective medicine and prevent unwanted bleeding events, we plan to implement 4T score as pre-test diagnostic tool in the EMR for physicians prior to ordering alternative anticoagulation for patients with low 4T's score. We also aim to decrease hospital cost by not only preventing unnecessary HIT panel tests, but also reduce cost spent on costly alternative anticoagulation. Whether SRA is a valuable test for patients with OD values between 1-2 remains uncertain. Limitations include small sample size and incomplete chart data given retrospective study.Reference: Lo GK, Juhl D, Warkentin TE, Sigouin CS, Eichler P, Greinacher A. Evaluation of pretest clinical score (4 T's) for the diagnosis of heparin-induced thrombocytopenia in two clinical settings. J Thromb Haemost 2006; 4: 759-65. DisclosuresNo relevant conflicts of interest to declare.

A 2 Year of Review of HIT Evaluations at an Urban Medical Center with an Aim Towards Quality Improvement and the Development of Practical Testing Strategies

Introduction:Thrombocytopenia is a common occurrence among inpatients while heparin-induced thrombocytopenia (HIT) is relatively rare and diagnostic strategies can vary. Our goal was to evaluate testing habits over a two year period at an urban tertiary care center.Methods:All cases with HIT panels over a two year period were reviewed to elucidate ordering patterns, test turnaround times, and areas for potential improvement. Sensitivities and specificities were determined for the 4T score, which was retrospectively calculated for all patients, the heparin/PF4 ab immunoassay (H/PF4), the SRA functional assay (SRA) and a combined low risk 4T and H/PF4 OD ratio less than 0.4. Average and median OD ratios were calculated for different levels of risk as determined by 4 T score. Given the lower risk of HIT in patients exposed to low molecular weight heparin (LWMH) (Martel et al. 2005) an exploratory analysis was made by which one point was deducted from the 4T for patients who were only exposed to LMWH during the HIT work-up admission.Results:245 patients received work-ups for HIT that included either a H/PF4 and/or an SRA, with 7 patients ultimately being determined to have HIT (yield of 2.86%). Workup issues included 28 incorrect tests being sent and a lack of 4T score documentation in the charts reviewed (15% with documentation, 38/245). Given that hematology consults were obtained in 60% (147/245) of the cases this was not a problem specific to primary inpatient teams.The sensitivities (SN) and specificities (SP) were as follows: for a low risk 4T score (SN 100%, SP 61.76%), for a low risk 4T after subtracting one point for sole exposure to LMWH (SN 100%, SP 63.03%), for the H/PF4 using Weak Positive as negative (SN 100%, SP 74.84%) for an OD<0.4 as negative (SN 100%, SP 79.05%), for the combined low risk 4T and OD<0.4 (SN 100%, SP 84.62%), for the SRA using Indeterminate as negative (SN 83.33%, SP 100%). Mean and median OD ratios by 4T risk category can be seen in the accompanying table and by score in the accompanying graph.Our calculated turnaround times for these tests were similar; 156 H/PF4 tests ordered for 146 patients took an average of 3.01 days to result, 229 SRA tests ordered for 212 patients took an average of 3.21 days to result. For the 55 HIT negative patients that ultimately received treatment the average length of therapy for those treated with argatroban was 5.11 days and for fondaparinux 7.11 days.Discussion:In an effort to improve the 4T score subtraction of 1 point for exposure to only LMWH was investigated with minimal improvement in specificity. However, 19 of the 23 patients in this category had a 4T score of four or less and this adjustment could have helped to avoid a sizable amount of subsequent testing (18 SRA's), imaging (5 studies) and alternate therapies (9 days total) if it moved these patients from intermediate to low risk.As is true in many hospitals, H/PF4's and SRA's are both send out tests in our institution and thus often ordered simultaneously. High turnaround times are also present in institutions where these tests are “batched” and only performed on certain days. With the small difference in test turnaround times it is worth questioning whether both tests are necessary to send concurrently in every case.One setting to evaluate simultaneous testing is in patients who are low risk by 4T and thus not switched from heparin to alternative agents. In these cases it is practical to not order any testing given the sensitivity of a low risk 4 T score. But when testing is opted for ordering only the H/PF4 and reserving the SRA for cases with OD ratios greater than 0.4 may be prudent. This is supported by the combined low risk 4T H/PF4 testing characteristics (Kim et al 2011). This strategy is already recommended but in institutions with long turnaround times simultaneous testing is much more common.In our cohort, 70 patients with low risk 4T scores had SRA's sent. Of these 70 patients, none of whom had HIT, 57 (81.4%) had H/PF4 ab OD ratios less than 0.40 and would not have needed additional testing. 57 SRA's could have been avoided and given that heparin can almost always be safely continued in these patients the potential costs of continuing alternate therapy are virtually non-existent.Conclusion:The low-cost, highly sensitive 4T remains a vital screening tool for HIT and while a low risk score should obviate the need for further testing our data supports that in cases where more testing is pursued a H/PF4 alone is the correct option. DisclosuresNo relevant conflicts of interest to declare.

Impact of Systems-Based Hematologists in Maintaining a HIT Program Using Continuous Clinical Audit and Education in an Academic Medical Center

Systems-based hematologists (SBH) play a vital role in navigating the health care system in the use of diagnostic tests that crosses multiple disciplines by implementing evidence-based strategies to improve patient safety and outcomes. In 2013, we demonstrated that an Anticoagulation and Bleeding Management Service (ABS) led by SBH played a major role in developing safe and cost-effective approaches for the diagnosis of patients with heparin-induced thrombocytopenia (HIT) via implementation of a centralized hospital-wide physician paper order protocol (Vaughn et al. Blood. Vol. 124, Abstract 4848). Platelet factor 4 (PF4) ELISA testing decreased from 600 in 2011 to 375 in 2013 (37.5% decrease), and serotonin release assay (SRA) testing decreased from 202 in 2011 to 29 in 2013 (85% decrease). In addition, 100% of patients with positive PF4 ELISA received an automatic consult by the ABS team to determine management of patients with suspected HIT. This led to a reduction in the use of direct thrombin inhibitors (DTI) by 78%. Despite this initial success, we were unsure if these improvements were sustainable moving forward.The purpose of this study was to provide quantitative data demonstrating the continuous impact that SBH have on health care delivery via annual re-auditing on PF4 ELISA testing to identify shortfalls and implement improvements as needed. In 2014, our institution switched to a new electronic medical record (EMR) system using EPIC in the inpatient environment. The 4T's Scoring Calculator physician paper order became obsolete. An electronic order set for PF4 ELISA test was in discussion but due to the complexity of switching to a new EMR system, this discussion was stalled. Now, physicians could order a PF4 ELISA test electronically without a 4T score. As a result, PF4 ELISA testing increased to 402 in 2014 and 632 in 2015. Ordering of SRA test, which was restricted to the ABS team, remained constant at 31 in 2014 and 36 in 2015.To overcome this, throughout 2015-2016, the ABS team gave specific feedback to the ordering physician when a false-positive PF4 ELISA test was ordered inappropriately. This allowed for individual discussion on each patient case to improve physicians' understanding and awareness of HIT testing and management. In addition, departmental-wide lectures on HIT/4T score to attending physicians and residents/fellows were scheduled.Despite these departmental-wide lectures, the ABS team found that ordering physicians remained unclear about calculation of the 4T score. Ordering physicians were calculating higher 4T scores and ordering PF4 ELISA based on their calculations. As a result, specific interactive lectures based on real-life case scenarios where the audience (internal medicine residents) calculated the 4T score for each scenario were given. This allowed for case-based discussions and opportunity for clarifying any uncertainty on the 4T score. Feedback from the residents was overwhelmingly positive. These efforts led to a reduction in PF4 ELISA test by 49% to 323 in 2016. A re-audit revealed that the number of PF4 ELISA test remained steady at 321 in 2017, which demonstrates the success of our interventions (Figure 1).In conclusion, this study highlights the important of re-auditing to maintain the improvements made. Despite initial success, annual re-auditing allowed for early detection of challenges, which then allowed appropriate early intervention. Administrative and financial support from the health care system for SBH allowed for the initiation, implementation and monitoring of this HIT program, and should be encouraged nationwide as a rewarding career opportunity for hematologists interested in hospital quality improvement and patient safety. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.