Use Of D-dimer Testing Research Articles

The combined use of D-dimer testing and the neutrophil-to-lymphocyte ratio in the early differential diagnosis of aortic dissection

ABSTRACT Background The study aimed to ascertain whether a diagnostic strategy combining D-dimer with the neutrophil-to-lymphocyte ratio (NLR) could improve the discriminative performance for aortic dissection (AD). Research design and methods Baseline levels of D-dimer and NLR were measured in patients suspected of AD. The diagnostic performance and clinical usefulness of D-dimer, NLR, and their combination were assessed and compared using receiver operating characteristics (ROC) curve analysis, logistic regression analysis, net reclassification improvement (NRI), integrated discrimination improvement (IDI), and decision curve analysis (DCA). Results The levels of D-dimer and NLR were both significantly higher in AD patients. The combined use displayed good discriminatory performance with an area under ROC curve (AUC) of 0.869, which was preferable to that of D-dimer. Although no meaningful improvement was found in the AUC by comparison with NLR alone, the combined use could significantly improve the discrimination power with a continuous NRI of 60.0% and an IDI of 4.9%. DCA demonstrated that the net benefit of the combined use was preferred over that of either single test. Conclusions The combined use of D-dimer and NLR could improve the discriminatory efficiency for AD with the potential in clinical application. This study may provide a novel diagnostic strategy for AD. More studies need to be done to confirm the findings of this study.

Прогностическая ценность D-димера у больных, перенесших инфаркт миокарда в условиях пандемии новой коронавирусной инфекции

In conditions of new coronavirus pandemic and high prevalence of myocarditis, myopericarditis, the issues of differential diagnosis, especially in patients who had previously undergone myocardial infarction, appear to be relevant. Against the background of COVID-19 both recurrent acute coronary disease and myocarditis, or myopericarditis are possible, and the differential diagnosis is significantly complicated by the similarity of clinical picture (pain in the heart area (not always typical), increased titers of cardiac troponins). Particular difficulties in diagnosis arise in patients who have undergone myocardial infarction, are in a coma and have unstable hemodynamics, since the detection of zones of local hypo- or akinesis on EchoCG has no proper diagnostic value; changes on ECG can be ambiguous; and the absolute majority of hospitals that provide care to COVID-19 patients have no possibilities of making MRI with gadolinium. In such cases, additional diagnostic methods may be helpful in making a definitive diagnosis. In such cases, additional diagnostic methods may be helpful in making a definitive diagnosis. The most available and well-studied laboratory indicator is D-dimer, which is a marker of hypercoagulation syndrome, however, some scientists also considered it as a marker of necrosis in myocardial infarction. This review shows the advantages and disadvantages of D-dimer in the diagnosis of acute coronary syndrome; the possibility of its use in patients with coronavirus infection, who had previously undergone myocardial infarction; the prospects for further research on this issue are outlined. The combined use of D-dimer test with electrocardiography, echocardiography, and clinical manifestations in patients with coronavirus infection to diagnose recurrent myocardial infarction was substantiated.

Performance Evaluation of the Quantitative Point-of-Care LumiraDx D-Dimer Test.

IntroductionFibrin degradation product d-dimer can be a valuable indicator for venous thromboembolism (VTE). The use of d-dimer testing in primary care settings can be limited by restricted access to laboratory services. This performance evaluation compares a quantitative, point-of-care (POC) d-dimer assay (LumiraDx d-Dimer Test) with a reference laboratory-based d-dimer assay.MethodsPlasma samples from patients presenting to secondary care in the UK, USA, and Germany were analyzed centrally using the LumiraDx d-Dimer Test and the reference test (bioMérieux VIDAS d-Dimer Exclusion II immunoassay). Method comparison used Passing–Bablok regression analysis with pre-specified equivalence criteria of r ≥ 0.9 and slope of 0.9–1.1. The NOVEL-3 study (NCT04375982) compared equivalency of fingerstick, venous blood (VB), and plasma samples from the same patient, tested at US primary care clinics next to the patient using the POC LumiraDx d-Dimer device. Measurements obtained from fingerstick and VB samples were compared with results from plasma samples, using Deming regression. The healthy reference range was determined using plasma samples of healthy volunteers, collected by commercial suppliers in Germany and the USA, which were analyzed centrally using the LumiraDx d-Dimer Test and the reference test.ResultsThe LumiraDx d-Dimer Test demonstrated agreement with the bioMérieux VIDAS d-Dimer Exclusion II immunoassay for plasma samples (r = 0.923, slope of 1.016, n = 1767). There was good agreement between fingerstick/VB samples and plasma samples (r = 0.980–0.986, n = 93) measured using the LumiraDx d-Dimer Test. Overall error rates were 1.8%. The healthy reference range 90% percentile for d-dimer was calculated as 533 µg/l fibrinogen equivalent units (FEU).ConclusionsThe quantitative LumiraDx d-Dimer Test is easy to use and can accurately measure d-dimer levels in a range of blood sample types, including fingerstick samples, which could improve assessment of VTE cases in community and hospital near-patient settings.

EVALUATION OF SCIENTIFIC AWARENESS OF MEDICAL FACULTY STUDENTS ABOUT COVID-19

Purpose: In the COVID-19 pandemic, a large number of physicians were needed. In order to meet possible physician needs, medical students should also be knowledgeable. The purpose of our study is to evaluate the awareness of different classes in our faculty about COVID-19.Material and Methods: This study is a multiple-choice questionnaire directed to students via a google form. In the first part, there are demographic questions, whether the student or a relative has had the disease, and in the second part, laboratory findings and questions about the diagnosis.Results: 334 students answered, and Croncbachs'Alpha (α) coefficient was 0.552 with 55% sample success. When the answers were analyzed according to the grades of the students, a significant difference was found between grade 2 and other grades (p<0.05). In all classes; The answer to the question "I do not agree" to the question "The most commonly used imaging method is computed tomography" is high. The question of where to get the swab sample is usually answered correctly, but the answer of "I have no idea" is high in 2nd graders. To the question of 'The primary target organ of Covid is the liver', the 2nd, 3rd grades gave a positive answer with a rate of 9.6%, 12%, and 14.7%, respectively. The questions of "use of D-dimer test" and "measurement of antibodies in serum" in the follow-up of the disease were mostly answered as "I have no idea" by the 2nd and 3rd grades.Conclusion: COVID-19 is not over yet and medical students need to be able to answer the questions posed to them by the society at different stages of the disease and follow-up period and make the right guidance. Especially the number of students who state that they have no idea about the imaging method and laboratory analysis questions is high. Additional courses on the subjects of pandemic management, filiation, diagnosis-follow up-treatment can be added to the curriculum of all classes in our medical faculty.

Hot Off the Press: Tell Me How To Diagnose a Pulmonary Embolism.

Pulmonary embolism (PE) is common and life-threatening Emergency Department (ED) diagnosis. Multiple validated risk stratification tools exist to help evaluate for PE and reduce unnecessary imaging. Despite these tools, there is still significant over-investigation for PE and low value testing persists. This study asks ED providers what are the barriers and facilitators to uptake of validated risk stratification tools in evaluation of PE.

Inappropriate use of D-dimer and impact on the test characteristics for deep vein thrombosis exclusion

This study aimed to investigate the prevalence of the inappropriate use of D-dimer testing for deep vein thrombosis (DVT) exclusion, and to evaluate the diagnostic value of D-dimer testing compared between testing in appropriate and inappropriate conditions. A retrospective chart review of patients with D-dimer requests at Siriraj Hospital, Bangkok, Thailand during January–September 2017 was performed. Data relating to D-dimer requests, Wells score, imaging investigations, and coexisting conditions that cause elevated D-dimer without correlation to DVT were analyzed. From 2196 cases, there were 300 D-dimer requests for DVT diagnosis. Of those, 5 (1.7%) and 158 (53.6%) requests were considered to be absolutely inappropriate D-dimer test requests due to the absence of pre-test Wells score evaluation and testing in DVT-likely patients, respectively. One-hundred and forty-eight (49.3%) requests were considered to be the relatively inappropriate D-dimer test requests due to testing in patients with coexisting conditions that included malignancies, sepsis, surgery, trauma, arterial thrombosis, and pregnancy. Three patients had more than one of these conditions. Comparatively higher negative predictive values (NPVs) of D-dimer assay for DVT exclusion were observed when used in DVT-unlikely (100% versus 80%), and in patients without coexisting conditions (100% versus 66.7%). The present study revealed the rate of inappropriate D-dimer testing for DVT exclusion to be high and this may lead to missed DVT diagnosis, overuse of imaging study, and unnecessary cost of D-dimer testing. Appropriate patient selection before test request can improve the NPV of D-dimer for DVT exclusion.

Venous Thromboembolism: Role of the Clinical Laboratory in Diagnosis and Management.

Venous thromboembolism (VTE) is the third most common cause of cardiovascular illness and is projected to double in incidence by 2050. It is a spectrum of disease that includes deep venous thrombosis (DVT) and pulmonary embolism (PE). In February 2016, the American College of Chest Physicians provided updated management guidelines for DVT and PE to address some of the unresolved questions from the previous version and to provide recommendations related to newer anticoagulants. Here we review current concepts for screening, diagnosis, thromboprophylaxis, and management of DVT and PE. We also describe the management of VTE in acute, long-term, and extended phases of treatment. Thrombophilia testing is rarely necessary and should be used judiciously; the laboratory can serve an important role in preventing unnecessary testing. The direct oral anticoagulants are as effective as conventional treatment and are preferred agents except in the case of cancer. The initial management of PE should be based on risk stratification including the use of D-dimer testing. Thrombolysis is used in cases of hemodynamically unstable PE and not for low-risk patients who can be treated on an outpatient basis. This review is intended to provide readers with updated guidelines for screening, testing, prophylaxis, and management from various organizations.

Overuse of Lower Extremity Venous Duplex by the Emergency Department for Detection of DVT: Pilot Study to Evaluate Use of D-Dimers as a Screening Tool in Low-Risk Patients

As the cost of health care remains a major concern for patients, providers, and payers, it has become increasingly important to evaluate resource utilization behaviors. The purpose of this study was to evaluate the utilization patterns of the emergency department in the ordering of lower extremity venous duplex ultrasound examinations for detection of acute deep venous thrombosis (DVT) and the use of D-dimer as a screening test in low-risk (by Wells criteria) patients. Estimated cost at our institution is $15 for the D-dimer test and $300 for the venous duplex ultrasound scan. All venous duplex ultrasound examinations that were ordered by the emergency department during the course of 10 days were evaluated. After-hours duplex ultrasound examinations were those ordered between the hours of 9 pm and 7 am on weekdays and between the hours of 4 pm and 7 am on weekends. Studies were evaluated for the patient’s presenting complaint, indication for duplex ultrasound as documented in the provider’s notes, results of the duplex ultrasound examination (positive vs negative for DVT), D-dimer studies, and Wells criteria scores. During this 10-day period, 68 lower extremity venous duplex ultrasound examinations were performed for emergency department patients, 28% of which were performed after hours (n = 19). Only 13% (n = 9) of these patients received concomitant D-dimer serum tests, of which 56% (5/9) of results were positive; 26 studies were bilateral, and only 5 studies were positive for acute DVT in one (n = 4) or both (n = 1) legs. Of 42 unilateral studies, only 9% (n = 4) were positive for acute DVT. Among patients with Wells criteria score <2, only 5 of 63 (8%) had a D-dimer sample sent. Among these, one had a positive duplex ultrasound scan. Five (8%) other positive duplex ultrasound scans occurring in the low-risk population did not have concomitant D-dimer samples sent. No patients with negative D-dimer results had acute DVT on duplex ultrasound examination. Based on the preliminary results of our pilot study, it appears there is significant overutilization of venous duplex ultrasound imaging by the emergency department for DVT screening with underutilization of D-dimer in low-risk patients. Use of D-dimer tests instead of duplex ultrasound scan in low-risk (Well criteria score <2) patients would have potentially saved $16,359 during a 10-day period, which would be approximately $597,104 per annum. Larger studies are recommended to examine the overuse of duplex ultrasound in the emergency department setting.

Usefulness of D-Dimer Testing in Predicting Recurrence in Elderly Patients with Unprovoked Venous Thromboembolism

BackgroundWhether post-anticoagulation D-dimer levels are useful in predicting recurrence in elderly patients with unprovoked venous thromboembolism is unknown. MethodsWe followed up 157 patients aged ≥65 years with acute symptomatic, unprovoked venous thromboembolism in a prospective, multicenter cohort study. All patients completed 3-12 months of anticoagulation and then underwent quantitative D-dimer testing (enzyme-linked immunosorbent assay) 12 months after the index venous thromboembolism. The outcome was recurrent symptomatic venous thromboembolism after D-dimer measurement. We examined associations between log-transformed and dichotomized D-dimer values and the time to venous thromboembolism recurrence using competing risk regression, adjusting for age, sex, and overt pulmonary embolism. ResultsThere was no statistically significant association between quantitative or dichotomized D-dimer levels and venous thromboembolism recurrence. The area under the receiver operating characteristic curve for predicting recurrent venous thromboembolism was moderate (0.66; 95% confidence interval [CI], 0.51-0.82). The negative likelihood ratios were 0.34 (95% CI, 0.05-2.38) at the usual and 0.34 (95% CI, 0.09-1.29) at the age-adjusted cutoff values. Among patients with normal D-dimer results, venous thromboembolism recurrence rates were 6.8 (95% CI, 2.2-21.2) per 100 patient-years using the usual and 7.1 (95% CI, 3.2-15.8) per 100 patient-years using the age-adjusted cutoff values. ConclusionD-dimer testing alone may not be useful in identifying elderly patients with unprovoked venous thromboembolism who are at low risk of recurrent venous thromboembolism and in whom anticoagulants may be safely stopped.

P136: A quality improvement initiative to optimize appropriate testing for venous thromboembolism in the emergency department

Introduction: Venous thromboembolism (VTE) is a common diagnostic consideration among patients presenting to the emergency department (ED) and often requires the use of diagnostic testing. A normal d-dimer (DD) blood test can exclude VTE and eliminate the need for costly imaging and the associated contrast medium and radiation exposure. The purpose of this quality improvement initiative was to increase the use of DD testing for patients with a low and intermediate clinical pretest probability of VTE, increase the use of ventilation perfusion scans (VQ) as an alternative to CT pulmonary angiogram (CTPA) and decrease the use of CTPA and venous doppler ultrasound (VDUS) at St. Michael’s hospital. Methods: A multispecialty team developed an ED specific algorithm set for appropriate VTE testing that were posted on the ED online portal along with a poster in each zone of the ED after an ED launch campaign with request for feedback. A run chart was used to track DD, CTPA, VQ and VDUS utilization. Two-sided T-test comparison was conducted to compare pre- and post-implementation utilization. Results: Physician feedback was positive regarding the use of: DD in VTE intermediate risk patients and the VTE algorithm set. Feedback was negative for DD turnaround time. We found a significant increase in DD use (77 tests per month to 93; p=0.013), but no significant change in the use of CTPA (27.3 per month to 30; p=0.38), VDUS, or VQ. Number of monthly ED visits remained constant. Conclusion: This intervention increased DD utilization, but measuring appropriateness will require prospective collection of clinical pre-test probability. Integrated risk stratification and decision aids into computer physician order entry may be necessary to track and improve appropriateness.

The Increasing Use of D-Dimer Testing in Suspected Pulmonary Embolism

The Increasing Use of D-Dimer Testing in Suspected Pulmonary Embolism

Clinical outcomes of venous thromboembolism with dalteparin therapy in multiple myeloma patients

This study focused on the clinical outcomes in multiple myeloma (MM) patients with venous thromboembolism (VTE) who received low-molecular-weight heparin (dalteparin) therapy. Changes in D-dimer levels before and after VTE were also evaluated. Among 549 patients treated with various chemotherapeutic agents, a total of 52 (9.47%) patients including 32 newly diagnosed with MM and 16 with relapsed/refractory MM developed VTE, 48 of whom received dalteparin. Among the 48 treated patients, 37 (77%) had proximal deep vein thrombosis (DVT), four had (8%) pulmonary embolism (PE), and seven (15%) had both DVT and PE. In 32 patients with available paired samples (at baseline and VTE occurrence), significant conversion of D-dimer levels from 2.2±0.4mg/L to 11.8±1.6mg/L (P<0.001) was observed, which decreased from 10.9±0.4mg/L to 1.9±0.6mg/L one month after initiating dalteparin therapy. A total of 44 patients received dalteparin with a median duration of 4.2months (range, 2.7–9.4), and four patients were discontinued early due to death (n=3) and major bleeding (n=1). After a median follow-up of 9.0months (range, 0.7–35.8) since the first VTE episode, five patients showed recurrence of VTE with a cumulative incidence of 17.5±7.9%. Major bleeding occurred in three patients. In summary, dalteparin seems to be a promising drug for the treatment of VTE in MM. In addition, the significant difference in D-dimer levels observed before occurrence of VTE and after dalteparin treatment may suggest the usefulness of D-dimer testing as a surrogate marker for VTE in MM patients.

Treatment results of venous thromboembolism with dalteparin in patients with multiple myeloma undergoing anti-myeloma chemotherapeutic agents

e198 the occurrence of VTE), significant conversion of d-dimer from 2.2 0.4 mg/L to 11.8 1.6 mg/L (P <0.001) was observed. At the time of data analysis, 7 patients are in dalteparin therapy and 37 patients finished dalteparin therapy with a median duration of 4.1 months (range, 2.7-8.4), and 4 patients early discontinued due to death (n1⁄43) and major bleeding (n1⁄41). With the improvement of clinical symptoms, d-dimer was decreased from 10.9 0.4 mg/L to 1.9 0.6 mg/L at 1 month after the initiation of dalteparin therapy. After a median follow-up of 8.7 months (range, 0.7-34.9) since a first episode of VTE, 5 patients showed the recurrence of VTE (the cumulative incidence; 18.3 8.1%). Major bleeding events were observed in 3 patients and one patient with nonfatal intracranial bleeding discontinued dalteparin therapy. Conclusion: Our study demonstrated the clinical outcome of anticoagulant therapy with dalteparin seems to be promising for the treatment of VTE in MM. In particular, the significant change of d-dimer was observed before occurrence of VTE and after dalteparin treatment in MM patients, suggesting the usefulness of d-dimer testing as a surrogate marker for VTE.

Symptom based approaches in point of care laboratory testing

Point of care testing (POCT) allows, among others, for efficient care of patients presenting with acute problems to primary care physicians. A combination of clinical information and laboratory results enables physicians to obtain posttest probabilities for the presence or absence of a specific disease. In order to rule in or rule out a disease, the physician has to know both the pretest probability for a disease in a patient as well as the analytical and diagnostic characteristics of the employed test. Pretest probability can be assessed by scores or by personal judgment of the experienced clinician. This article presents the basics of the Bayes theorem together with its clinical applications in acute scenarios in primary health care. These scenarios comprise the use of D-Dimer testing in ruling out venous thromboembolism, rapid testing of group A streptococci in the setting of acute pharyngitis, troponin testing in patients with thoracic pain, c-reactive protein (CRP) testing in patients presenting with acute cough and fever, as well as urine dipstick testing in suspected urinary tract infection. These examples illustrate, that risk stratification before conducting laboratory analysis is of utmost importance in order to obtain valid results for ruling in or ruling out diseases in POCT-settings.

Appropriate Use of d-Dimer Testing Can Minimize Over-Utilization of Venous Duplex Ultrasound in a Contemporary High-Volume Hospital

The sensitivity of d-dimer (DD) in detecting deep venous thrombosis (DVT) is remarkably high; however, many institutions send patients immediately for a venous duplex ultrasound (VDU). This study was designed to examine the appropriate utilization of DD and VDU in a high-volume hospital. A retrospective study was conducted on consecutive patients who presented to a high-volume emergency department (ED) with lower extremity limb swelling/pain over a 30-day period, who were sent for VDU during an evaluation for DVT. VDU data were merged with electronic DD laboratory results. The enzyme-linked immunosorbent assay method was used to provide DD values and thresholds. Values above 0.60 mg/fibrinogen equivalent unit (FEU) were considered abnormal. We reviewed the medical records of 517 ED patients in the month of June 2013. After applying the Wells criteria, 157 patients (30.4%) were excluded because of a history of DVT or pulmonary embolism, having been screened for shortness of breath, or sent for surveillance-leaving 360 for analysis. The average age was 59.3 ± 16.5 years with more women (210, 58.3%) and the majority reported limb pain or swelling (73.9%). DD was performed on 51 patients with an average value of 3.6 ± 5.4 mg/FEU, of which 43 (84.3%) were positive. DD identified all positive and negative DVT patients (100% sensitivity and negative predictive value), but also included 40 false positives (16.7% specificity). On the other hand, 309 patients were sent directly to VDU without DD; of those, 43 (13.9%) were positive for DVT. However, 266 (86.1%) patients were negative for DVT by VDU without DD and these were deemed improper by our current study protocol. Potential charge savings were calculated as VDU for all (360 × $1000 = $360,000), DD for all (360 × $145 = $52,200), and VDU for both true and false positives (estimated to be about 25% of the cases; 90 × $1000 = $90,000); this equals a charge savings of $217,800 and would avoid unnecessary VDUs. Based on the results of our study, we suggest that the DD test be utilized during the initial work-up for patients with limb swelling/pain in the emergency room. Appropriate utilization of DD, as well as other clinical criteria, may limit the over-utilization and added cost of VDU, without a negative impact on patient care. The results of DD tests should be utilized to limit the number of patients sent for VDU to only those patients with a positive DD or other significant underlying concerns.

D-dimer testing for suspected venous thromboembolism in the emergency department. Consensus document of AcEMC, CISMEL, SIBioC, and SIMeL

D-dimer testing is currently considered a cornerstone in the diagnostic approach of patients with suspected venous thromboembolism (VTE) across different health-care settings, including the emergency department (ED). Nevertheless, inappropriate or incorrect activities developing throughout the total testing process may substantially impair the clinical usefulness of this test and delay or even challenge the fast rule out or diagnosis of VTE. The leading problem of D-dimer is represented by the poor specificity for diagnosing VTE, wherein a minority of patients with a positive D-dimer are finally diagnosed with VTE, and even more importantly, the specificity further decreases with ageing, thus contributing to increase the overcrowding in short stay units such as the ED. Due to the large heterogeneity that characterizes the use of D-dimer in the emergency room, three Italian societies of laboratory medicine (Italian Committee for Standardization of Hematology and Laboratory Methods, Italian Society of Clinical Biochemistry and Molecular Biology, and Italian Society of Laboratory Medicine), along with the Academy of Emergency Medicine and Care, have developed a consensus document about the use of D-dimer testing for diagnostics of patients with suspected VTE in this health-care setting. The evidence-based indications contained in this document will cover the leading preanalytical, analytical, and postanalytical issues that may impair the clinical efficacy of D-dimer testing in the ED.

Update of D-dimer testing1)

Abstract D-dimer concentrations are elevated in a variety of clinical situations with hypercoagulability, such as venous thromboembolism (VTE), disseminated intravascular coagulation (DIC), ischemic cardiopathy, stroke, acute aortic dissection, malignomas, pregnancy, after surgery, traumas, and burns. D-dimer testing has become an essential tool for the diagnosis of VTE and pulmonary embolism because of its high negative predictive value, especially when used in conjunction with a clinical pretest score. D-dimer testing can be used for the diagnosis of DIC and other thrombotic diseases. It is also helpful for risk stratification in coronary artery disease, in first and recurrent thrombotic events, and for the timing of the duration of oral anticoagulation after a first episode of VTE. The use of D-dimer testing is limited in certain clinical conditions in which elevated D-dimer concentrations render the test unsuitable for the detection of acute thrombotic events.

383 Impact of a Clinical Guideline on Utilization of CT Angiograms in Emergency Department Patients Evaluated for Pulmonary Embolism

Contrast-enhanced computed tomography angiogram studies are used with increased frequency in the emergency department (ED) to evaluate patients for pulmonary embolism without a significant increase in the overall rate of PE diagnoses. We sought to measure the impact of an ED clinical guideline incorporating the use of D-dimer testing and pre-test clinical suspicion assessment on the utilization of computed tomography angiogram studies and subsequent positive rate for pulmonary embolism.

A Randomized, Controlled Trial of Varying D-Dimer Cutpoints According to Clinical Pretest Probability Compared with a Uniform D-Dimer Cutpoint for Diagnosis of Deep Vein Thrombosis

AbstractAbstract 5116 Background:D-dimer assays are currently used as a one-size-fits-all diagnostic test for DVT where the same cutpoint is used to define a positive result for all patients. This approach ignores the relationship between the diagnostic properties of the assay and the pretest probability of the disease. Objective:We conducted a randomized, allocation concealed, controlled, assessor-blinded trial to compare the safety and efficiency of two diagnostic strategies for D-dimer testing for first acute DVT of the lower limb: Selective use of D-dimer testing, using different D-dimer cutpoint levels according to clinical pretest probability (C-PTP) and the traditional Uniform approach. Method:1723 consecutive eligible inpatients and outpatients at 5 clinical centres (4 in Ontario, 1 in Montreal) had their C-PTP assessed using the Wells' Score and were randomized to either: Uniform D-dimer testing, in which all patients had a D-dimer test and a level of <0.5 μ g fibrinogen equivalent units (FEU)/mL was classified as negative (the control group); or Selective D-dimer testing, in which D-dimer testing was (a) performed in patients with Low and Moderate C-PTP only, (patients with a High C-PTP had an ultrasound, but no D-dimer testing), and (b) was classified as negative if the D-dimer level was <0.5 μ g FEU/mL with Moderate C-PTP or <1.0 μ g FEU/mL with Low C-PTP (the experimental group). The D-dimer assays used in this study were the MDA D-Dimer (bioMerieux, Inc and Trinity Biotech) and STA Liatest D-Dimer(Diagnostica Stago). All patients with a positive D-dimer had an ultrasound of their leg. Symptomatic venous thromboembolic events (VTE) during 3 months of follow-up were objectively confirmed and independently adjudicated. Results:The incidence of VTE during 3 months of follow-up in patients who were not diagnosed with DVT at initial presentation was 1.1% (9/811) with Uniform testing, and 1.1% (9/814) with Selective testing (difference 0.004%, 95% CI:-1.122, 1.111). The incidence of VTE during 3 months of follow-up in patients in the Low C-PTP Select arm (D-dimer cutpoint 1.0 μ g FEU/mL) was 0% (0/356), and in the Low C-PTP Uniform arm (D-dimer cutpoint 0.5 μ g FEU/mL), it was 0.3% (1/336). Conclusion:This is the first randomized controlled clinical trial to show that Selective use of D-dimer testing, with a higher D-dimer cutpoint in patients with Low C-PTP, is safe and potentially more efficient than current practice. Funded by the Heart & Stroke Foundation of Ontario. Disclosures:Linkins:Trinity Biotech: in-kind donation of D-dimer kits; BioMerieux: in-kind donation of D-dimer kits; Stago Diagnostica: in-kind donation of D-dimer kits. Bates:bioMerieux: in-kind donation of D-dimer kits; Trinity Biotech: Consultancy, in-kind donation of D-dimer kits. Kearon:BioMerieux: in-kind donation of D-dimer kits; Trinity Biotech: in-kind donation of D-dimer kits; Stago Diagnostica: in-kind donation of D-dimer kits.

Inappropriate use and interpretation of D-dimer testing in the emergency department: an unexpected adverse effect of meeting the “4-h target”

Introduction:D-dimer tests were inappropriately overused in our emergency department as a result of bloods being taken before clinical assessment to help meet the “4-hour target”. We introduced a multifaceted intervention...