Comparison of immunonephelometry and electroimmunoassay for estimation of plasma apolipoprotein A-I

Immunonephelometry using a helium-neon laser as light-sources has been compared with the established technique of electroimmunoassay for estimation of plasma apolipoprotein A-I (apoA-I), the major protein component of high density lipoproteins (HDL). The within-batch coefficient of variation for immunonephelometry was 6.7% and for electroimmunoassay was 4.7%, but both methods showed similar between-batch precisions (6.9% and 7.0% respectively). Plasma from 122 subjects (62 male, 60 female) were analysed by both methods. Results showed good correlation but immunonephelometry gave consistently lower apoA-I values (mean +/- 1 S.D. = 1.32 +/- 0.25 g/l) than did electroimmunoassay (1.56 +/- 0.33 g/l). Plasma apoA-I concentrations obtained by both procedures were significantly higher (P less than 0.002) in females than in males. Both assays gave results which were highly correlated with high density lipoprotein cholesterol. Immunonephelometry is therefore considered to be satisfactory for estimation of plasma apoA-I concentration.