B-054 The impact of hemolysis on lipase result: Does it clinically matter?

Abstract Background Roche Diagnostics recently lowered the hemolysis index (HI) interference threshold for lipase from 1000 (10 g/L) to 100 (1 g/L) hemoglobin, but there was limited supporting data communicated to support this change. This large threshold decrease significantly increases the sensitivity to interference for the lipase assay, potentially requiring result reporting changes that would slow laboratory workflow and impact result interpretation. To verify the new HI claim, we performed an interference study by targeting clinically relevant lipase concentrations. Methods Five lipase concentrations of residual lithium heparin plasma samples (36-227 U/L, n=3-5) were spiked with increasing concentrations of hemoglobin prepared from lysed red blood cells (0, 0.5, 1, 2, 3, 4, 5, 8, 10, 12 g/L). Lipase was measured in triplicate and HI results were measured in singleton on a Roche Cobas Pro c503 instrument. Results are expressed as mean ± standard deviation. Interference was calculated as the absolute and percent differences from the 0 g/L control. Interference was compared against the allowable total error (ATE) from various sources: 1) 12 U/L if 60 U/L or 20% if =60 U/L (RCPA), 2) 12.9% (EFLM), 3) 30% (CAP), and 4) 8 U/L if 40 U/L or 20% if =40 U/L (IQMH). Results At 1 g/L hemoglobin, the HI was 95±4, and yielded a 0.4-1.0% difference from baseline across all lipase concentrations. At the lowest lipase concentration group (38±2 U/L), results were falsely elevated starting at 3 g/L hemoglobin (HI=289 ± 18) when ELFM and IQMH ATE were used, while no difference was found when RCPA and CAP ATE were used up to 12 g/L hemoglobin (HI=1171±22). At other lipase concentrations, differences were all within ATE limits from all sources. Conclusion Hemolysis affected lipase results in a lipase concentration-dependent manner with an analytically significant impact found only when lipase concentration was 40 U/L. The clinical impact is minimal at this concentration as this is well within the normal reference interval for lipase. No changes to the hemolysis rules on the instrument were implemented. This study highlights the importance of verifying manufacturer claims and assessing change impact at a clinical level.