Abstract Number: PB2287
Meeting: ISTH 2020 Congress
Background: D-dimer is used to rule out venous thromboembolism (VTE) in outpatients with a low pre-test probability of VTE and incorporated into clinical decision rules to determine recurrence risk in patients after an unprovoked VTE. To increase D-dimer specificity and reduce the number of patients requiring imaging, recent studies have suggested a clinically “adjusted” D-dimer cut-off based on patient age, or clinical probability of having VTE rather than a fixed assay-specific cut off. D-dimer assays are not standardized and expressed in different units. The use of universal VTE exclusion thresholds and differences in assay variability raises concerns about the generalizability of recent studies using specific D-dimer assays, and the effect on clinical decision rules.
Aims: To review the diagnostic performance of D-dimer assays based on external proficiency data in a large international cohort of laboratories.
Methods: From 2017 to 2019, the global External Quality Assessment programme of the ECAT Foundation distributed 24 D-dimer positive samples quarterly, to participating laboratories, mainly from Europe, North America and Australia who analyzed the samples and reported results to ECAT. Consensus values for 6 samples were at the D-dimer cut-off level of 0.5 mg/L FEU (or DDU equivalent), 8 were slightly elevated and 10 were clearly elevated above that cut-off.
Results: Between 578 and 640 of enrolled laboratories per year participated in the D-dimer surveys (response rates of 88-95%) using up to 35 unique assays. Over 65% of samples were assessed using three main assays as seen in the most recent survey of 2019 (Table 1). For D-dimer samples around the cut-off, the variability in individual assays for the same sample, was much higher than for samples clearly elevated above the cut-off (Table 2).
Conclusions: Increasing between participant variability for the same sample at the cut-off raises concerns about the diagnostic performance of D-dimer assays at VTE exclusion thresholds.
|Samples with D-dimer at or just above cut off of 0.5 mg/L FEU or 0.25 mg/L DDU||Samples with D-dimer clearly above cut off of 0.5 mg/L FEU or 0.25 mg/L DDU|
|Assay||Samples assessed (2017-2019) n||Range of assigned value (mg/L)||Between participant variability CV Range (%)||Samples assessed (2017-2019) n||Range of assigned value (mg/L)||Between participant variability CV Range (%)|
|Siemens Innovance D-dimer (FEU mg/L)||1795||0.41-0.71||7.6-12.5||2918||0.75-1.85||5.4-8.4|
|I.L. HemosIL D-dimer HS500 (FEU mg/L)||578||0.37-0.5||9-17.3||922||0.70-1.7||5.7-10.2|
|Stago Liatest D-dimer Plus (FEU mg/L)||573||0.37-0.55||12.4-19||616||0.73-2.13||4.3-9.3|
|I.L. HemosIL D-dimer HS (DDU mg/L)||265||0.2-0.23||8.8-21.2||438||0.25-0.63||4.3-22.3|
|Roche Tinaquant 2nd gen (cal heparin) (FEU mg/L)||196||0.3-0.37||21.3-38.7||308||0.38-1.29||7.3-23.1|
|BioMerieux Vidas D-dimer (FEU mg/L)||191||0.36-0.53||5.3-6.8||318||0.69-2.1||3.7-7.9|
|Stago/ Roche Liatest D-dimer (FEU mg/L)||239||0.38-0.5||12.1-21.1||411||0.73-2.16||4.9-9.4|
[Table 2: Between Participant variability in samples AT or CLEARLY ABOVE above the VTE exclusion cut-off]
|Assay||Unit||Proportion of samples assessed using this assay (%)|
|Siemens Innovance D-dimer||mg/L FEU||39.3|
|I.L. HemosIL D-dimer HS500||mg/L FEU||15.1|
|Stago Liatest D-dimer Plus||mg/L FEU||13.1|
|I.L. HemosIL D-dimer HS||mg/L DDU||4.9|
|Roche Tinaquant 2nd gen (cal heparin)||mg/L FEU||4.2|
|BioMerieux Vidas D-dimer||mg/L FEU||3.5|
|Stago/ Roche Liatest D-dimer||mg/L FEU||3.4|
|Other*||mg/L FEU OR mg/L DDU||16.5|
|FEU – Fibrinogen Equivalent Units DDU – D-dimer Units *Included in this group are assays with 25 or less samples tested per assay|
[Table 1: Commonest assays in use in the last sample survey of 2019 (Total – 801 samples analyzed and reported)]
To cite this abstract in AMA style:Elbaz C, Meijer P, van Essen-Hollestelle M, Liederman Z, Selby R. D-dimer Diagnostics: An International Assessment of the Quality of Laboratory Testing [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/d-dimer-diagnostics-an-international-assessment-of-the-quality-of-laboratory-testing/. Accessed August 15, 2022.
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