Reporting of D-Dimer and performance of analytical systems: Data from participants to the External Quality Assessment Scheme of the Biomedical Research Centre in Italy

Abstract

Introduction: D-Dimer assessment represents a cornerstone in the diagnostic approach to several thrombotic disorders. Recent literature has highlighted the role of D-Dimer also in the diagnostic pathway of coronavirus infection (COVID-19) and the importance of harmonized reporting [D-dimer unit (DDU) or fibrinogen equivalent unit (FEU);unit of measure;cut-off] in order to guarantee the correct interpretation of the results. Methods: D-Dimer data from 100 EQA participants and the inter-laboratory variability (CV%) of the last 7 years for the most used analytical systems: Werfen, HemosIL HS;Werfen, HemosIL HS-500;Auto D-D, Sclavo;Innovance, Siemens;VIDAS, bioMerieux and STA Liatest, Stago have been evaluated. Results: Concerning the results expression in DDU or FEU, we observed a prevalence of FEU (55.1%) over DDU (44.9%);the value was confirmed in the last 7 years (average FEU = 55.6%), differently from data obtained in the survey conducted in 2014 at a national level. The units used are: ng/mL (67.8%), μg/L (29.0%) and mg/L (3.2%) for D-Dimer DDU;ng/mL (57.9%), μg/mL (21.0%), μg/L (15.8%) and mg/L (5.3%) for D-Dimer FEU. Inter-laboratory variability (mean CV%) calculated on a total of 72 controls is lower for all diagnostic systems at pathological levels than the one observed for concentrations below the cut-off. Discussion: This study demonstrates that the reporting of D-Dimer results does not comply with the 2014 SIBioC consensus document which recommended the use of μg/L FEU, and highlights 8 different types of information. Data reported in this study call for the harmonization of D-Dimer reporting in order to guarantee the correct interpretation of the information, both in the case of COVID-19 and in all the diseases already known where this analyte has a clinical relevance.