engleski

Effect of hemolysis on routine coagulation assays

BACKGROUND: Hemolysis might affect the reliability of laboratory testing and is reported to be the leading source of unsuitable specimens. Our aim was to investigate the effect of in vitro hemolysis on routine coagulation parameters. MATERIALS AND METHODS: We studied 50 pairs of hemolyzed and subsequently re-collected non-hemolyzed plasma samples within individual patients. The time interval between the two collections was recorded. Hemolysis and approximate hemoglobin concentration were assessed by visual inspection, comparing samples against a standard color scale. According to hemoglobin concentration, hemolyzed samples were divided into 4 subgroups: slightly (0.5 g/L), mildly (1 g/L), moderately (2 g/L) and severely (>3.0 g/L). PT, APTT and fibrinogen were determined in all samples immediately after collection, using an automated analyzer. Differences between hemolyzed and corresponding non-hemolyzed specimens were evaluated. The effect of hemolysis was expressed as interfering bias and compared to analytical quality specifications and reference change values to define analytically and clinically relevant variations. RESULTS: Statistically significant overestimation of PT values was observed in all investigated subgroups. APTT (seconds) was significantly shortened only in the severely hemolyzed subgroup (23.9 (22.0 - 27.8) vs. 26.5 (24.0 - 29.1), P=0.002). Likewise, fibrinogen concentrations (g/L) were overestimated in the severe hemolysis subgroup (4.5 (3.7 – 5.5) vs. 4.4 (3.5 - 5.5), P=0.005). The mean interfering biases were heterogeneous for all assayed parameters, independent of hemolysis degree. When compared to desirable specifications, investigated parameters showed no analytically or clinically relevant variation. CONCLUSIONS: Although the differences between hemolyzed and non hemolyzed specimens observed in this study were not analytically nor clinically relevant, they were heterogeneous and unpredictable, which emphasizes the need to thoroughly investigate this issue and eventually revise, standardize and harmonize procedures for management of unsuitable samples in coagulation testing.

Hemolysis; coagulation testing; unsuitable specimens.

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