Impact of the nature of anticoagulant on the determination of gamma glutamyl transferase activity in blood

Abstract

Background - Gamma-glutamyl transferase (GGT) is routinely used as a highly sensitive marker of hepatobiliary disease, alcohol consumption and more recently as predictive biomarker of cardiovascular events. In current practice, laboratories measure the GGT activity on tube containing lithium heparin. Except that there is no evidence that GGT activity can be reliably determined with this anticoagulant. The purpose of this study is to evaluate the impact of the anticoagulant on the determination the GGT activity in blood samples. Methods - Blood samples of 30 patients were collected in three types of tubes: dry tube, tube containing lithium heparinate and another containing dipotassium ethylene diamine tetraacetate (K2-EDTA). The statistical analysis includes correlation studies, Bland Altman’s analysis, as well as the comparison of biases to analytical change limit (ACL) and reference change value (RCV). Results - Results obtained on heparinized plasma are globally overestimated comparatively to the serum (p=0.001). Whereas, the results obtained on EDTA plasma are more comparable to those of serum (p=0.356). Taking the dry tube as a reference, the calculated bias for heparinized plasma (+49.55%) samples is larger than the ACL (5.24%) and the RCV (37.52%). For EDTA plasma samples, this bias (-13.40%) is lower than RCV, but higher than ACL. Conclusion - Our results show that the determination of GGT activity must be done on serum samples. If ever plasma should be used, we recommend collecting specimens on EDTA anticoagulant.

Keywords

• Gamma glutamyl transferase
• pre-analytical variables
• influence of anticoagulants
• Lithium heparinate