Reference limits of apolipoprotein A-I and apolipoprotein B using an IFCC standardized immunonephelometric method

An important collaborative study organized by the IFCC enabled the selection of international reference materials and the standardization of commercially available methods by the use of common calibrators. In this paper, we report the reference limits of apolipoprotein A-I and apolipoprotein B in a selected healthy French population. The apolipoprotein measurements were performed on BNA Behring using reagents and protocols supplied by the manufacturer: the standard sera were calibrated using the IFCC-WHO reference preparations (SP1 and SP3). In addition, the apolipoprotein B protocol was modified by the addition of a supplementary reagent to reduce the interference by lipaemic samples on immunonephelometric measurement. In a sample of 115 random serum samples, there was a decrease in mean concentration between non-standardized and standardized methods: -4.8% for apolipoprotein A-I and -4.7% for apolipoprotein B. The reference limits for apolipoprotein A-I are unaffected by gender between 4 and 14 years, thereafter vary with age and gender until 40 years and with gender alone between 40 and 60 years. For apolipoprotein B, the variation with gender is only significant between 30 and 49 years.