Biological variability of lipoprotein-associated phospholipase A2 activity in healthy individuals

Measuring lipoprotein-associated phospholipase A2 (Lp-PLA2) activity can aid in identifying individuals at higher risk of coronary heart disease. However, the biological variation of Lp-PLA2 activity and corresponding reference change value (RCV) is unknown which limits interpretation of results. In this study we aim to define the intra- and inter-individual variability of Lp-PLA2 activity in a healthy reference population. A total of 24 healthy individuals (22–47years of age) were prospectively collected at several time points: daily for five days (after overnight fast), daily for three days (while non-fasting), weekly for four weeks (after overnight fast), and monthly for 6months (after overnight fast). Intra-individual and inter-individual variability was determined. The index of individuality (IoI) and reference change value (RCV) were calculated for each time period. Variability in Lp-PLA2 activity was not different in fasting versus non-fasting states and also did not change in daily versus monthly testing. The RCV for monthly Lp-PLA2 activity was found to be 17%. More than 90% of the variability was attributable to between person differences while analytic variability comprised