Biological variation of proprotein convertase subtilisin/kexin type 9 (PCSK9) in human serum.

Abstract Background Proprotein convertase subtilisin/kexin type 9 (PCSK9) is involved in the regulation of LDL receptors. Inhibition of PCSK9 increase uptake of LDL-particles and pathogen-associated molecular patterns (PAMPs). The aim of our study was to evaluate biological variation of serum PCSK9. Methods Within-subject (CVI) and between-subject (CVG) biological variations were assessed in 14 healthy volunteers in a 6-week protocol (7 samples, equidistant time intervals). Serum concentration of PCSK9 was measured by a Quantikine ELISA assay (R&D systems, Bio-Techne Ltd., UK) on a DS2 ELISA reader (Dynex Technologies GmbH, Germany). Precision (CVA) was assessed by duplicate measurements. Two methods with different levels of robustness were used for the estimation of CVI, SD-ANOVA and CV-ANOVA method. We calculated the index of individuality and reference change values. The experiment was fully compliant with EFLM database checklist. Results The within-subject values of PCSK9 in healthy persons, as calculated by two statistical methods, were 23.2% (SD-ANOVA with CVA of 5.6%) and 26.6% (CV-ANOVA with CVA of 4.8%). The CVG was 10.9% (SD-ANOVA), index of individuality and RCV were 2.13 and 66.3%, respectively. Conclusions The high index of individuality indicates that common reference intervals can be used to interpret serum PSCK9 values.