Background: Coagulation factors activity testing is necessary for the diagnosis and treatment of patients with hemostasis disorders and requires relevant analytical goals to promote accuracy and precision across multiple methods.
Aims: This work evaluates Prothrombin Time (ProT) and Activated Partial Thromboplastin Time (aPTT) differential factors (DF) assays state-of-the-art, from results of an External Quality Assessment (EQA) program provided by ProBioQual , a french proficiency testing association.
Methods: Factors (F) II, V,VII ,X ,VIII ,IX ,XI ,XII were measured each year on 20 lyophilized human citrated plasmas by participant laboratories (160 for FXII to 450 for FV in each survey) for the 2019-2021 period. Statistical evaluation was performed according to the ISO13528:2015 guideline and Robust Algorithm A. The consensus value was calculated for all participants (AP) results and each peer group (PG). The imprecision of methods was evaluated by the inter-laboratory 90th percentile coefficient of variation (CV90) for AP and each PG. Inaccuracy was quantified as 90th percentile bias (bias90) of laboratory results from AP or PG consensus value.
Results: ProT DF CVs do not change significantly with level and vary between 7 and 8% for FII and FX, 8 and 9% for FV and FVII. The AP and PG bias90 are very close and the lowest for FII and FX (around 12%). AP CVs are the highest for FVIII, FIX and FXII, respectively 14%, 17% and 13%, for a level close to 40%; PG CVs fall to 10%. AP bias90 is always higher than than PG bias90 for aPTT DF and reachs 20% at normal level, 22% at low level for FVIII and FIX; PG bias90 is respectively 14% and 17%.
Conclusion(s): Performance of ProT DF tests is satisfactory in routine practice. For aPTT DF assays, EQA survey results show a lack of standardization across multiple instrument-reagent combinations.
