Performance of semiquantitative and quantitative D-dimer assays in the ECAT External Quality Assessment Program

D-dimer levels are used in clinical practice as markers for the presence or exclusion of venous thrombosis. Therefore, it is important that the perfor mance of the D-dimer tests is well controlled. One of the components of a laboratory quality program is external quality a ssessment (EQA), The main aim of EQA is to identify the degree of agreement among laboratories. In addition to identifying the individual laboratory p erformance, it also identifies the characteristics of the different reagent s and methods that are used in different laboratories. Recently, the D-dime r test was included in the ECAT External Quality Assessment program. Eighty-one laboratories in four rounds applied semiquantitative and quantit ative D-dimer assays to three samples (concentrations normal, slightly elev ated, and elevated). Although the reported values varied widely, the classi fication of the samples was mostly correct for the normal and the elevated samples. The slightly elevated sample was classified as normal by all labor atories using semiquantitative methods and by 60% of the laboratories using quantitative methods, and this varied between 45% and 86% for the differen t methods. In conclusion, D-dimer methods show a large variation, and the quality of t he D-dimer assessment could be improved by standardization and by using cut -off ranges.