Automated Hemostasis Tests Affected By Hemolysis, Icterus And Lipemia

One of the requirements for a clinical laboratory is that common interferences related to sample integrity such as hemolysis, icterus and lipemia (HIL) be evaluated with each reagent system and because of limited resources and budgetary constraints, the clinical laboratory relies on the manufacturer to document HIL estimates.

Scientists at the Royal Hallamshire Hospital (Sheffield, UK) and their French colleagues collected blood samples for testing plasma-based coagulation assays and molecular hemostasis assays. They assessed the influence of HIL on prothrombin time (PT), activated partial thromboplastin time (APTT) and fibrinogen assay using a viscosity-based detection analyzer (VBDS). Interference of hemolysis was studied in two different ways: spontaneous in vitro hemolysis judged to have occurred during sample collection transport or processing and spurious hemolysis.

The level of hemolysis was semi-quantitatively estimated based on the measurement of hemoglobin concentration using a XN-10 (Sysmex Corporation, Kobe, Japan). All the coagulation assays were performed using reagents and a STA-Compact-Max analyzer (Stago, Asnières sur Seine, France). One reagent, Stago’s STA-Liquid Fib, titrated human calcium thrombin, was used for the measurement of fibrinogen.

The scientists found that spontaneous hemolysis that occurred during sample collection and processing had no effect on PT with either a rabbit tissue factor extract or recombinant human tissue factor reagents. In contrast, addition of mechanically hemolysis cells impacted on PT for the highest hemoglobin concentration. For APTTs there was no significant difference between results in hemolysed and nonhemolysed samples. For the other two reagents studied, APTTs were statistically significantly shorter in hemolysed samples compared with nonhemolysed samples. This bias was clinically significant only for STA-PTT Automate reagent. For all three APTT reagents, the impact of hemolysis was sufficient to impact patient management decisions, and in some samples, the effects of lipemia and icterus were not clinically significant.

The authors concluded that their results confirm that PT and fibrinogen are not clinically significantly affected by HIL. The APTTs of some haemolysed samples were falsely normal with one reagent and more affected than two others. Hemolysed samples should be continuously rejected. Conversely, from a clinical standpoint, lipemia and icterus did not significantly affect APTT measured with the different reagents tested in combination with a VBDS analyzer.

Related Links:
Royal Hallamshire Hospital
Sysmex
Stago