Abstract:

Objective To investigate the failures of activated partial thromboplastin time（APTT） external quality assessment（EQA）,and to analyze the problems in EQA.Methods The results of EQA and failures were analyzed step by step. According to the Clinical and Laboratory Standards Institute（CLSI） H47-A2 guideline,the intrinsic pathway factor responsiveness of domestic reagent（ellagic acid） and original reagent（ellagic acid） was analyzed. The APTT responsiveness in percent activity（%） could be determined from the intersection of curve and the upper limit of APTT normal reference range.Results All of the results were positive bias,and the samples with failures were low-value samples. The laboratory documentations were normal in the EQA month. The experimental operators strictly followed the standards of operation. The EQA materials were normal. The reported data showed that EQA coagulation items were classified according to instruments,not according to reagents/instruments. The APTT responsiveness of domestic reagent was FⅧ 54.0%,FⅨ37.3%,FⅪ 56.5% and FⅫ 36.4%. The APTT responsiveness of original reagent was FⅧ 42.9%,FⅨ 30.0%,FⅪ 45.3% and FⅫ 28.4%.Conclusions The failures of APTT EQA are caused by the difference of intrinsic pathway factor responsiveness between original and domestic reagents. The item of APTT should not only be grouped by instruments, but also be grouped by reagents/instruments to avoid false judgement for participating laboratories.

Key words: Activated partial thromboplastin time, External quality assessment, Failure cause, Factor responsiveness