Hemolysis interference in 10 coagulation assays on an instrument with viscosity-based, chromogenic, and turbidimetric...

Hemolysate in plasma samples from patients may cause misleading results in coagulation assays. Even though modern coagulation instruments often are equipped with modules that can detect hemolysis, icterus, and lipemia (HIL), studies that report the influence of these interferences are still limited. The present paper focuses on the influence of hemolysis on 10 coagulation assays.

Artificial hemolysis was created by freezing/thawing, and the hemolysates generated were added to pools of patient plasma. Pathological and normal levels were pooled separately. These spiked samples were analyzed on a STA R Max 2 instrument. The coagulation assays evaluated utilize clot, chromogenic, or immunoturbidimetric detection.

Four of the evaluated assays were not influenced by hemolysis: fibrinogen, von Willebrand factor antigen, activated partial thromboplastin time, and factor VIII. Interestingly, normal and slightly elevated prothrombin time (INR < 2.0) was insensitive to hemolysis, whereas samples with a high INR (≥2.0) exhibited falsely high readings. The assays for antithrombin and fibrin D-dimer displayed an intermediate sensitivity to hemolysis. The most sensitive assay turned out to be anti-Xa, followed by protein C and protein S. For the anti-Xa assay, the results are decreased by 10% already at 0.5 g/L hemoglobin.

The present study shows that hemolysis affects several of commonly used coagulation assays. Since the sensitivity for hemolysis is dependent on the brand of the assay as well as the instrument and principle of measurement, it is necessary to evaluate the influence of each specific combination.