Assessment of enzyme measurement procedures in China through a trueness verification program

Background: Since 2003, the National Center for Clinical Laboratories (NCCL) has organized a network of reference laboratories and several survey programs to improve standardization in China.

Methods: We analyzed the 2015 trueness verification program to assess the status of enzyme measurement standardization. Commutable serum-based materials were prepared and sent to 10 reference laboratories to assign target values for 2 enzymes (alanine aminotransferase-pyridoxal phosphate [ALT-pp] and γ-glutamyltransferase [GGT]) using IFCC reference measurement procedures.

Results: Analytical performance was assessed for compliance to 3 indexes: trueness (bias), imprecision (CV), and accuracy (total error). Of the 250 participating laboratories, about half (≥124) used heterogeneous systems. More laboratories met the tolerance limit of imprecision than of trueness or accuracy. Except at the lowest concentration, the CV pass rates were >90% for the 2 enzymes. The optimal performance criterion derived from biological variation yielded pass rates for total error (ALT 77%, GGT 80%) that were higher than for bias (ALT 63%, GGT 73%).

Conclusions: PT/EQA results for commutable samples can be used to assess trueness against reference measurement procedures. Despite global and national standardization programs, bias remains a critical limitation of current enzyme measurement procedures in China.