Quantitative D-dimer Assay Research Articles

The performance of quantitative D-dimer assays in Chinese clinical laboratories by analyzing data from National External quality Assessment Scheme

Background and aimsTo investigate performance of D-dimer assays in China and address analytical quality issues. Materials and methodsD-dimer assays data were collected from China National External Quality Assessment Scheme (China NEQAS) from 2014 to 2022. We analyzed reagents, assay results, reporting unit and cutoffs in 2022 China NEQAS. Interlaboratory coefficient variations (CVs) and influence of modified/unmodified test systems on CVs were investigated over 9 years. ResultsThere were 82 reagent brands in China NEQAS, but 55 reagent instructions did not indicate expression unit (DDU or FEU). Up to 7-fold of the ratio of max-to-min mean results was shown among different assays with same unit on the same sample. A prevalence of FEU (63.4%) over DDU (17.1%) was observed. Although 669 laboratories (37.9%) among 1766 laboratories used reagents without VTE exclusion claim, they also reported cutoffs. The CVs of only two assays were decreasing over years. CVs of modified test systems were higher than those of unmodified systems before improvement. ConclusionsExpression unit should be required to label in package inserts by regulatory authority. Laboratory professionals should follow instructions for use and prefer unmodified test systems for clinical safely application. Harmonization of reporting units through collaborative efforts is the promising step.

The Utility of Quantitative D-Dimer Assay as a Biomarker in the Diagnosis and Exclusion of Cerebral Venous Sinus Thrombosis.

The utility and sensitivity of quantitative D-Dimer assay to rule out the diagnosis of deep vein thrombosis is well established. We extrapolated this principle to evaluate the utility of D-Dimer assay in exclusion of cerebral venous sinus thrombosis (CVST). As advanced imaging modalities required for the diagnosis of CVST might not be available everywhere, it is important to have a sensitive biomarker and a clinical decision rule which can assist in the diagnosis. Patients undergoing CT/MR Venography of the brain with the suspicion of CVST were enrolled. Quantitative D-Dimer assay was performed in those who had CVST on CT/MR Venography and was compared with those who did not. A Clinical decision rule for the diagnosis of CVST was formulated using logistic regression analysis. Receiver operating characteristic analysis evaluating the diagnostic accuracy of D Dimer for patients with CVST as compared to those who did not revealed an AUROC of 0.694. D-Dimer levels of < 300ng/mL had a sensitivity of 90% for the exclusion of CVST. After logistic regression analysis, a clinical decision rule with a total score of 16 and individual components of Female gender (2 points), Headache (7 points), D-Dimer levels of ≥ 792ng/mL (7 points) was proposed. D-Dimer had a poor diagnostic accuracy for differentiation of patients who had CVST from those who did not, however, had a high sensitivity at values < 300ng/mL. The proposed clinical decision rule with a score of ≥ 9 had a good diagnostic accuracy in prediction of CVST (AUROC = 0.809).

Performance of the Quantitative Latex Immunoturbidimetric D-dimer Assay for the Diagnosis of Acute Pulmonary Embolism at Rafik Hariri University Hospital

Background and aims: The diagnostic workup for pulmonary embolism (PE) includes D-dimer assay and computed tomographic angiography. Several D-dimer assays have been approved for PE diagnosis with different sensitivity and specificity. We aimed to study the sensitivity and specificity of the quantitative latex agglutination D-dimer assay used in a referral teaching hospital in Lebanon for the diagnosis of acute PE. Methods: Using a retrospective chart review, we studied 300 patients who had D-dimer test at Rafik Hariri University Hospital in the period between January 1, 2012 and December 31, 2013. Accordingly, 93 patients had a CT angiography after being suspected to have acute PE. A statistical table 2*2 was used to compare the results of CT angiography and D-dimer test. Results: Thirteen patients (13.97%) had PE and 60 patients (64.51%) had positive D-dimer test. Quantitative latex agglutination D-dimer assay had a sensitivity of 69%, specificity of 36%, and negative predictive value of 88%. False positive ratio was also 64%. Moreover, the receiver operating characteristic (ROC) curve was obtained with an area under the curve measuring 0.527. Conclusion: Quantitative latex agglutination D-dimer assay has a high negative predictive value; thus, it can exclude a PE diagnosis if it is associated with low clinical pretest probability.

Highly Elevated Quantitative D-Dimer Assay Values Increase the Likelihood of Venous Thromboembolism.

Objectives In patients with suspected venous thromboembolism (VTE), the D-dimer assay is commonly utilized as part of the workup. The assay is primarily used to determine whether to proceed with radiographic imaging. We compared D-dimer levels in patients suspected of having VTE. We hypothesized that higher D-dimer values predict a higher likelihood of subsequent VTE diagnosis. Methods We conducted a secondary analysis of a multinational, prospective observational study of low- to intermediate-risk adult patients presenting to the emergency department with suspicion of VTE. Demographic and clinical data were collected in a structured manner. Advanced imaging including ultrasound, computed tomography (CT) pulmonary angiography, and ventilation/perfusion scanning was obtained at the discretion of the treating physicians. Imaging was evaluated by board-certified radiologists in real time. D-dimer values' bins were evaluated using a logistic regression model. Results We evaluated 1,752 patients for suspected deep vein thrombosis (DVT), with 191 (10.4%) DVT positive. We evaluated 1,834 patients for suspected pulmonary embolism (PE), with 108 (5.9%) PE positive. Higher D-dimer values in both groups were associated with higher likelihood of subsequent VTE diagnosis, with D-dimer values > 3,999 ng/mL in both groups having the highest incidence of VTE. More than 50% of those patients were VTE positive. Conclusions Increasing D-dimer values predict increased likelihood of being found VTE positive in this patient population. Among those in the highest D-dimer category, > 3,999 ng/mL, over half of patients were VTE positive. Further research could determine additional nuance in D-dimer as a tool to work up suspected VTE.

Evaluation of point-of-care testing for D-dimer in elderly patients

Objective To evaluate the clinical performance of AQT90 FLEX, a novel time-resolved fluorescence based point-of-care test (POCT) for quantification of D-dimer in elderly patients. Methods The method from Quantitative D-dimer assay (WS/T 477-2015) for testing equipment performance was used as a reference to evaluate the clinical performance of AQT90 FLEX. The correlation was compared between testing results of D-dimer using the AQT90 immune-assay analyzer and those using the ACL TOP coagulation analyzer. Results At high concentration of D-dimer, the within-run precision coefficient of variation (CV) was 2.619%, and at low concentration of D-dimer, the within-run precision CV was 2.767%. The pollution-carrying rate was 0.12%. The measured data from AQT90 and ACL TOP had a correlation coefficient of r=0.9491(P <0.01). The equation of the line of best fit for D-dimer with which all AQT90 results can be adapted to the ACL TOP was: AQT90=2.52 ACL TOP + 0.15. The number from the equation was slightly greater in female than that in male, and it was also increased in elderly. Conclusions The AQT90 FLEX had rational precision and linearity in determination of concentration. There was a high agreement between the testing results from AQT90 and those from ACL TOP. It was recommended to use a slope of 2.52 and an intercept of 0.15 to adjust the D-dimer values of the ACL TOP to the AQT90 FLEX assay systems. POCT for D-dimer by AQT90 FLEX raises feasibility for use in elderly patients. Key words: D-dimer; AQT90 FLEX immunoassay analyzer; ACL TOP Coagulation analyzer

Clinical evaluation of eight different D-dimer tests for the exclusion of deep venous thrombosis in primary care patients

D-dimer tests are an essential element in the diagnostic work-up of deep venous thrombosis (DVT). However, the poor standardization amongst assays necessitates clinical validation before implementation in daily practice. We therefore evaluated the analytical and diagnostic performance of eight D-dimer tests in a representative group of 290 prospectively identified consecutive primary care patients with suspected DVT. Seven quantitative D-dimer assays, and a qualitative test, Simplify, were evaluated. Correlation between assays was generally poor and several assays showed a significant bias in the method comparison. Nevertheless, the Vidas D-dimer, Innovance D-dimer (CA1500 and BCS), Pathfast D-dimer, and HemosIL HS500 (ACL TOP), all displayed 100% (95% CI: 85–100%) sensitivity. Tina-quant (Modular), AQT90 D-dimer, and Liatest (STA®) D-dimer tests showed a slightly lower sensitivity of 95% (78–100%). and the Simplify test reached a sensitivity of 91% (72–99%) that was further improved in combination with a clinical decision rule to 95% (76–100%). In concert with the low (8.2%) prevalence of proximal DVT, diagnosed by compression ultrasonography, in our study, all test reached a negative predictive value (NPV) of at least 99%. The user friendliness of the assays differed mainly by stability of reagents, calibration frequency, time required to obtain a test result and costs of a test. In conclusion, despite considerable analytical differences, in our low-risk population all tests evaluated displayed an excellent NPV. In combination with a validated clinical decision rule to identify low-risk patients, even a straightforward POC solution could safely and cost-efficiently rule out DVT.

Adapting the D-dimer cutoff for thrombosis detection in elderly outpatients

D-dimer measurement is an important step in diagnostic strategies for venous thromboembolism. It allows the safe ruling out of the diagnosis with no need for imaging tests in approximately 30% of outpatients. However, the usefulness of d-dimer is limited in elderly patients; the likelihood of a negative d-dimer strongly decreases with age, making physicians reluctant to order the test. Several attempts to improve the performance of d-dimer in elderly patients have been pursued. Recently, an age-adjusted cutoff was derived; the optimal cutoff value (in µg/l) appears to be equal to the patient’s age (in years) multiplied by ten in patients over 50 years of age with a low pretest clinical risk of venous thromboembolism. This age-adjusted cutoff value has been extensively and externally validated in retrospective studies that included mostly outpatients with suspected deep vein thrombosis or pulmonary embolism and used various quantitative d-dimer assays. All available studies confirmed the increased usefulness and similar safety of the age-adjusted cutoff compared with the conventional cutoff, the most important benefit being obtained in elderly patients. However, before any recommendation for clinical practice can be made, a prospective diagnostic management outcome study is lacking, in which all low clinical risk patients with d-dimer levels below their age-adjusted cutoff would be left untreated with no further diagnostic testing.

Clinical usefulness of adjusted D-dimer cut-off values to exclude pulmonary embolism in a community hospital emergency department patient population

Plasma D-dimer measurement is used in the assessment of the clinical probability of pulmonary embolism (PE), in order to minimize the requirement for pulmonary computed tomography angiography (CTA). To evaluate whether doubling the threshold value of serum D-dimer from 500 μg/L to 1000 μg/L could safely reduce utilization of pulmonary CTA to exclude PE in our emergency department patient population. Emergency department patients evaluated for PE with a quantitative D-dimer assay and pulmonary CTA were eligible for inclusion. D-dimer values were retrospectively collected in all included patients. Pulmonary CT angiograms were reviewed and scored as positive or negative for PE. Receiver-operating characteristic (ROC) analysis was used to determine the accuracy of quantitative D-dimer measurements in differentiating between positive and negative PE patients as per CTA. A total of 237 consecutive patients underwent pulmonary CTA and had a D-dimer measurement performed. Median D-dimer level was 1007 μg/L and in 11 (5%) patients the pulmonary CT CTA was positive for PE. The ROC curve showed an area under the curve (AUC) of 0.91 (P < 0.0001). Increasing the D-dimer threshold value of 500 μg/L to 1000 μg/L increased the specificity from 8% to 52% without changing the sensitivity. Adjusting the D-dimer cut-off value for the emergency department community population and patient age increases the yield and specificity of the ELISA D-dimer assay for the exclusion of PE without reducing sensitivity.

Venous thromboembolism and coagulation activity in patients with immune thrombocytopenia treated with thrombopoietin receptor agonists

Venous thromboembolism and coagulation activity in patients with immune thrombocytopenia treated with thrombopoietin receptor agonists

Computed tomography angiography in patients with suspected pulmonary embolism—too often considered?

BackgroundPulmonary embolism (PE) is a major cause of morbidity and mortality associated with surgery and medical illnesses. In recent years, pulmonary computed tomography angiography (CTA) has become the diagnostic method of choice. However, it remains unclear when to perform CTA and how often a decision based on clinical judgment results in positive or negative findings. MethodsIn a retrospective study, 261 patients admitted for suspected PE were evaluated with pulmonary CTA. Decisions to order CTA were based on clinical judgment and optionally quantitative d-dimer assays. Clinical, radiologic, and laboratory data were revisited and compared in patients with and without proven PE. ResultsThe patients' mean age was 63 ± 1 years; almost 30% of all participants had at least a moderately reduced renal function. Pulmonary CTA demonstrated PE in only 14.9%; both age and sex distribution was comparable in the PE and non-PE group. Proximal deep vein thrombosis or pathologic chest x-rays were significantly more likely in patients with PE (P < .001 and P < .05), whereas echocardiography results were comparable. d-dimer values were noticeably higher in the PE group (P < .001); however, C-reactive protein and troponin T levels were not helpful. ConclusionsPulmonary CTA confirmed PE in only a minority of patients and may be overused. Clinical judgment in conjunction with d-dimer evaluation was of limited help to predict positive results but surprisingly comparable with previous results using pretest probability scoring systems. Using present and previous data, a simplified enhanced algorithm is proposed to reduce use of CTA.

Cost-Effective Diagnostic Strategies in Patients With a High, Intermediate, or Low Clinical Probability of Pulmonary Embolism

Rapid quantitative D-dimer assays (DD), lower extremity venous duplex ultrasonography (US), and multislice computed tomographic (CT) angiography have been shown to have adequate sensitivities and specificities for diagnostic purpose. The purpose of this study was to evaluate cost-effectiveness of diagnostic strategies for pulmonary embolism (PE) in patients with a high, intermediate, or low clinical probability of PE. A formal cost-effectiveness analysis for the diagnosis of PE was performed. The main outcome measure for effectiveness was 3-month expected survival. The strategy of DD followed by CT was cost-effective and had the lowest cost per life saved for all patients suspected with PE. The conventional strategy including ventilation and perfusion lung scanning followed by pulmonary angiography (PA) or CT was not cost-effective. The leg US after CT was not also cost-effective. In clinical practice, the individual patient's condition should be considered when choosing appropriate diagnostic tests.

Limited Utility of a Rapid Quantitative Enzyme-Linked Fluorescent Assay for the D-Dimer in the Diagnosis of Overt Disseminated Intravascular Coagulation

The role of quantitative D-dimer assay in screening for and diagnosing overt disseminated intravascular coagulation (DIC), conventionally diagnosed by the International Society of Thrombosis and Haemostasis' (ISTH) score, was evaluated. Of patients with clinical conditions associated with overt DIC, 142 with ISTH scores ≥5 (compatible with overt DIC) and 61 with ISTH scores <5 (suggestive of nonovert DIC) underwent the quantitative D-dimer assay. Accuracy indices, receiver operating characteristic (ROC) curve-derived cutoffs, and areas under curve were compared. Mean D-dimer level in overt DIC was 4147.2 ± 2707 ng/mL. In nonovert DIC, it was 1678.9 ± 1888.3 ng/mL. Both were higher than healthy controls (229.6 ± 129.9 ng/mL). An optimized cutoff (2040 ng/mL) had relatively low sensitivity (75.4%) and specificity (73.8%). Extensive overlap between groups at this cutoff reduced diagnostic utility. Lowered cutoffs increased sensitivity (eg, 91.5% at 1000 ng/mL) but diminished specificity (59%), limiting use of screening. In conclusion, the quantitative D-dimer as a stand-alone assay has a limited role in diagnosis of overt DIC.

The diagnostic performance of APC–PCI complex determination compared to d-dimer in the diagnosis of deep vein thrombosis

D-dimer testing is widely used as part of the diagnostic algorithm for the exclusion of deep vein thrombosis (DVT) but is considered of limited in value for ruling DVT in. Since D-dimers are poorly defined, there is no standardization of the assays and this makes reliable comparisons between clinical studies difficult. We report on a performance evaluation of a new marker of activated coagulation (Activated Protein-C in complex with Protein-C inhibitor, APC-PCI complex) compared to two quantitative D-dimer assays (Vidas D-dimer Exclusion and Autodimer). The post-hoc comparison was made on 350 frozen plasma samples from consecutive outpatients suspected of DVT in a multicenter management study including clinical probability score, D-dimer testing, venous ultrasound and contrast venography as part of the diagnostic algorithm. The APC-PCI complex performed inferior to the D-dimer assays in terms of sensitivity: 74 vs. >93%, negative predictive value: 91 vs. >96% and area under the curve: 0.82 vs. 0.9, but showed a significantly higher specificity: 80 vs. 40-60%. Specificity for the APC-PCI complex did not decrease with higher clinical probability score and the positive predictive value was significantly higher than that of the D-dimer assays in the intermediate/high probability cohort (66 vs. <52%). In this probability cohort, high levels of the APC-PCI complex and to a lesser extent, D-dimers, can give positive predictive values of >90% in up to 20% of the patients which indicates important clinical implications. However, for the exclusion of DVT at the pre-specified cut-off level, the APC-PCI complex perform inferior to the D-dimer assays in this study.

Computed Tomography Angiography in Patients Evaluated for Acute Pulmonary Embolism with Low Serum D-dimer Levels: A Prospective Study

Pulmonary computed tomography angiography (CTA) and the Wells criteria both have interobserver variability in the assessment of pulmonary embolism (PE). Quantitative D-dimer assay findings have been shown to have a high negative predictive value in patients with low pretest probability of PE. Evaluate roles for clinical probability and CTA in Emergency Department (ED) patients suspected of acute PE but having a low serum D-dimer level. Prospective observational study of ED patients with possible PE who underwent pulmonary CTA and had D-dimer levels </=1.0 mug/mL. Clinical probability of PE determined by ED physicians using standard published criteria; pulmonary CTAs read by initial and study radiologists kept unaware of D-dimer results. In 16 months, 744 patients underwent pulmonary CTA, with 347 study participants who had a D-dimer level </= 1.0 mug/mL. In one participant, CTA showed a PE that was agreed on by both the initial and study radiologists. In six participants, the initial findings were reported as positive for PE but were not interpreted as positive by the study radiologist. In none of these participants was PE diagnosed on the basis of clinical probability, of findings on ancillary studies and three-month follow-up examination, or by another radiologist, unaware of findings, acting as a tiebreaker. Pulmonary CTA findings positive for acute embolism should be viewed with caution, especially if the suspected PE is in a distal segmental or subsegmental artery in a patient with a serum D-dimer level of </=1.0 mug/mL. Furthermore, the Wells criteria may be of limited additional value in this group of patients with low D-dimer levels because most will have low or intermediate clinical probability of PE.

Performance of two relatively new quantitative D-dimer assays (Innovance D-dimer and AxSYM D-dimer) for the exclusion of deep vein thrombosis

Introduction D-dimer assays are now widely used as the first-line test in the diagnostic algorithm of suspected deep vein thrombosis (DVT). The aim of this study was to evaluate the performance of two relatively new quantitative D-Dimer assays (Innovance™ and AxSYM®) by comparison with a clinical gold standard. Patients and methods 311 samples from outpatients with clinical suspicion of DVT, included in a prospective management study, was analysed (prevalence of DVT 23%). The diagnostic workup included estimation of pre-test probability, D-dimer determination, objective imaging as well as 3 month clinical follow up of negative patients. Results No significant differences were seen in sensitivity and negative predictive values between Innovance, AxSYM and the reference assays. The area under the ROC curve was slightly lower for the AxSYM assay and the correlation to the reference assays was only moderate (r < 0.8) whereas the agreement with the Vidas assay was near excellent (κ = 0.8). The Innovance assay reached the highest AUC, showed a strong correlation with the reference assays (r ≥ 0.9) and a good agreement with the Vidas assay (κ = 0.76). In combination with a low pre-test probability score the Innovance assay reached a NPV of 100% (95% CI, 92-100) and the AxSYM assay 98% (95% CI, 87-100). Conclusion The Innovance and AxSYM assays show an overall good and comparable performance for the exclusion of DVT when compared to the established assays. Our results for the AxSYM assay indicate that the optimal cut-off value needs to be further evaluated.

D-Dimers and Efficacy of Clinical Risk Estimation Algorithms: Sensitivity in Evaluation of Acute Pulmonary Embolism

The goal of this study was to test the efficacy of clinical risk algorithms and a quantitative immunoturbidimetric D-dimer assay in the evaluation of patients undergoing pulmonary CT angiography for suspected acute pulmonary embolism. From April 1, 2007, to March 31, 2008, emergency department evaluations for clinically suspected pulmonary embolism were performed with the revised Geneva score, a quantitative D-dimer assay, and pulmonary CT angiography. Evaluations for pulmonary embolism were performed for 745 consecutively registered patients, 627 of whom were included in the study. The other 118 patients were excluded because a d-dimer assay was not performed. According to the revised Geneva score, 281 patients had low clinical probability of having pulmonary embolism; 330, intermediate probability; and 16, high probability. CT angiography showed that 28 patients had pulmonary embolism (six in the low-probability group, 17 in the intermediate-probability group, and five in the high-probability group). The sensitivity, negative predictive value, and specificity of the D-dimer assay were 100%, 100%, and 25% (low-clinical-probability group); 100%, 100%, and 33% (intermediate-probability group); and 80%, 80%, and 37% (high-probability group). The data appear to support the use of a quantitative D-dimer assay as a first-line test in evaluation for pulmonary embolism when the clinical probability of the presence of pulmonary embolism is low or intermediate. The sensitivity and negative predictive value were 100% for these cases. More than 26% of CT angiographic examinations might have been avoided if the D-dimer assay had been used as a first-line test in the care of patients at low or intermediate risk. Because of the small sample size, the D-dimer assay is not recommended as a first-line test in the evaluation of patients at high risk.

Deep Vein Thrombosis in Stroke Patients Admitted to a Rehabilitation Unit in Singapore

Studies have shown that deep vein thrombosis (DVT) is common after an acute stroke. Less common are studies documenting DVT in stroke patients admitted to rehabilitation. The purpose of this study was to determine the frequency and risk factors of DVT in stroke patients admitted to a rehabilitation unit in Singapore. A prospective observational single-center study of patients with ischemic and hemorrhagic stroke with lower limb paresis admitted to a rehabilitation center in Singapore. The screening protocol consisted of quantitative D-dimer assay (DDA) within 24-48 h of rehabilitation admission followed by duplex ultrasound scan of the paretic lower extremity if DDA level was elevated (equal or greater than 0.34 microg/ml). Altogether, 341 patients were screened at a mean of 23 days poststroke. One hundred and ninety-eight (58.1%) patients had an elevated DDA and all underwent ultrasound scans. The frequency of lower limb DVT was 9% (18) - seven proximal and 11 distal. DVT was significantly related to higher D-dimer levels (P=0.029) and cortical strokes (P=0.004), but not to age, gender, race, nature of stroke, atrial fibrillation, severity of lower limb weakness, and ambulatory and functional status. No patients had clinical pulmonary embolism during rehabilitation. Lower limb DVT is uncommon in stroke patients admitted to rehabilitation in Singapore. Future research should include evaluation of the cost-effectiveness of such a screening protocol.

Deep Venous Thrombosis in Asian Traumatic Brain Injury Patients During Rehabilitation

To determine the prevalence and risk factors of asymptomatic lower-limb deep venous thrombosis (DVT) among Asians in inpatient rehabilitation after traumatic brain injury (TBI). a prospective observational study. Fifty-six (35 males and 21 females) Asian individuals with TBI with a median of 25 days to rehabilitation. The mean age was 49.3 +/- 20.4 years and 64.3% (36) were Chinese, 19.6% (11) were Malay, 10.7% (6) were Indian, and 5.4% (3) were of other races. quantitative D-dimer assay (DDA) and targeted hemiplegic/weaker lower extremity venous duplex ultrasonography (VDU) for patients with elevated DDA levels (>or=0.34 microg/mL). Outcome measures included the incidence of DVT based on VDU diagnosis. All 34 (60.7%) patients who had elevated DDA levels underwent single limb VDU, revealing an incidence of 5.4% (3) of lower-limb DVT, including 1 case of proximal and 2 of distal DVT. Logistic regression analyses did not reveal any significant predictive factors for DVT, but tracheostomy, higher admission Glasgow Coma Scale (GCS) score, and lower Functional Independence Measure (FIM)-walk scores correlated significantly with elevated DDA levels (P < .05). Receiver-operating characteristic analysis showed that cutoff DDA levels of 1.37 mg/mL resulted in a sensitivity of 100% and a specificity of 67.7%. Asymptomatic DVT is uncommon in Asian TBI rehabilitation patients. Our low incidence could be related to the small sample size, ethnic protective factors, early walking during rehabilitation, and timing of VDU during possible declining thrombotic risk.

Comparison of high specificity with standard versions of a quantitative latex D-dimer test in the assessment of community pulmonary embolism: HaemosIL D-dimer HS and Pulmonary Embolism

Background D-dimer assays are sensitive but have poor specificity. False positive results lead to extra imaging and hospital admissions. Objectives To make a pilot comparison of the diagnostic accuracy of the standard quantitative latex HemosIL D-dimer assay with a newer HemosIL D-dimer HS version designed to have improved specificity. Patients / Methods Consecutive patients presenting from the community to an Emergency Department that were investigated for suspected pulmonary embolism using a D-dimer test were included in the study. Standard and D-dimer HS tests were performed. Pulmonary Embolism was diagnosed on the basis of imaging studies or post-mortem at any time from presentation to 90 days thereafter. Results The prevalence of Pulmonary Embolism was 4.5% (18/402). The sensitivity, specificity, negative predictive value, and positive predictive value for the standard quantitative D-dimer test was 100% (81.5 – 100.0), 49.2% (44.1 – 54.3),100% (98.1 – 100.0), and 8.5% (5.1 – 13.0), respectively, and 100% (81.5 – 100.0), 58.3% (53.2 – 63.3),100% (98.4 – 100.0), and 10.1% (6.1 – 15.5), for the D-dimer HS test. There were 35 (16%) fewer ‘false positives’ using the D-dimer HS assay compared with the standard assay. Conclusions D-dimer HS has superior specificity to the standard quantitative D-dimer test without any loss of sensitivity. The generation of fewer false positive results should lead to less unnecessary diagnostic imaging; the use of which is associated with increased hospital admissions and length of stay. The HS assay may therefore have significant health economic benefits.

Evaluation of the Innovance D-DIMER analytical performance

Widespread use of D-dimer in recent years has led to the development of a number of new fully automated quantitative D-dimer assays. We evaluated the analytical performance of the particle-enhanced immunoturbidimetric assay Innovance D-DIMER (Siemens Medical Solutions) on the Behring Coagulation System (BCS) analyzer. Within-run coefficients of variation (CVs) for samples with low, borderline, slightly, and extremely increased D-dimer concentrations were 2.1%-5.5%, whereas between-run CVs for control samples with low and extremely increased D-dimer were 5.5%-8.4%. The assay exhibited good linearity in the working range between 0.17 mg/L and 5.45 mg/L fibrinogen equivalent units (FEU), with the lower limit of detection of 0.099 mg/L FEU. The upper reference value determined in 40 plasma samples from healthy volunteers was 0.495 mg/L FEU. The results obtained in 457 fresh plasma samples were compared with results obtained with VIDAS D-Dimer Exclusion. Passing and Bablok regression analysis demonstrated highly significant correlation (y=1.370x-0.108, r=0.952, p<0.001). Bland and Altman difference plots demonstrated slightly higher results obtained with Innovance D-DIMER that was more pronounced with increasing values. Very good agreement between both assays was observed (kappa=0.860; 95% confidence interval (CI), 0.811-0.908). This study demonstrates that Innovance D-DIMER fulfills all analytical requirements for daily routine use.