[Biological inter- and intra-individual variations of serum immunochemical constituents and their allowable limits of analytical error]

The biological inter- and intra-individual variations of serum immunochemical constituents were estimated by the analysis of variance. Twelve samples taken at weekly intervals were analyzed for 22 healthy individuals. As for immunoglobulin (Ig) G, IgA, IgM, IgE, C-reactive protein, anti-streptolysin O, alpha-fetoprotein, complement component 3 and 4, and ferritin, the intra-individual variations (with coefficient of variations (CVs) ranging from 4.8% to 51.7%) were smaller than the inter-individual variations (with CVs ranging from 14.6% to 107.6%). The values for carcinoembryonic antigen (with CVs of inter- and intra-individual variation being 31.6% and 39.6%, respectively) and beta 2-microglobulin (with CVs of inter- and intra-individual variation being 14.4% and 13.1%, respectively) were similar. The biological variations of serum immunochemical constituents, examined in this study, were larger than those of serum chemical constituents. Based on our data, we propose allowable limits of analytical error, which is less than one-half of the average intra-individual variation for evaluation of imprecision and is less than one-quarter of the inter- plus intra-individual variation for evaluation of inaccuracy.