Study of Analytical Error in Lipase Assay

BACKGROUND: Lipase and amylase are the most frequently used biomarker for the diagnosis of pancreatic diseases, especially acute pancreatitis. Lipase has better diagnostic accuracy in comparison to amylase for the analysis of acute pancreatitis. However, lipase assay in random access analyzer is sometimes difficult to perform as it is exposed to different types of samples or reagents which may act as interference. MATERIALS AND METHODS: In our laboratory, we found the raised values (>500 IU/L) of lipase with normal amylase in some samples. However, the immediate rerun of these samples for lipase only showed normal (<80 IU/L) lipase level. To root out this fallacy, we performed reagent and sample carryover studies. RESULTS: The cause of the falsely raised value of lipase was revealed by reagent carryover studies. All samples which assayed triglyceride (TGL) followed by lipase immediately after it showed elevated (>500 IU/L) lipase value. This is due to the interference of microbial lipase used in TGL reagents. This was corrected by separating the analysis of lipase and TGL into two different instruments. CONCLUSION: If interference testing is not done, the laboratories are prone to have an analytical error in reporting and hence lead to diagnostic error. Hence, after analyzer installation, interference testing should be included in the validation protocol.