Calibration, specificity and trueness of a postheparin plasma lipoprotein lipase assay

Measurement of lipoprotein lipase activity in postheparin plasma is general ly accompanied by moderate within-run variation CVW-R (< 10%) and higher be tween-run variation CVB-R (5-25%). A calibration system was introduced in o rder to improve the reproducibility of measurements and to compare lipoprot ein lipase activities from different days. Every day a calibration curve fo r lipoprotein lipase activity was constructed. Fifteen calibration curves d esigned over 2 years, show linearity over the whole biological spectrum and a considerable reduction of between-run variation in lipoprotein lipase ac tivity, from 42% to 5.3% as estimated from two control postheparin plasma s amples. The lipoprotein lipase calibration system is an easy and very cheap arrange ment, which makes it possible to compare lipoprotein lipase activities achi eved over years. When the lipoprotein lipase control values are compared wi th reference lipoprotein lipase samples determined in other lipase laborato ries, the calibration-control system becomes an important tool for reducing analytical bias. The article reviews the original analytical criteria of catalytic measureme nt of lipoprotein lipase activity and describes the implementation of the c alibration-control system. We describe a model for reduction of the analytical variability in the meas urement of lipoprotein lipase activity. Other standardization efforts need to be made in the future, especially to define the reference material for c alibration.