lmmunoadsorption assay for bone alkaline phosphatase compared with wheat germ agglutinin precipitation assay in serum from (pre)pubertal girls

The performance characteristics of two bone alkaline phosphatase (ALP; EC 3.1.3.1) assays, a wheat germ agglutinin (WGA) precipitation assay and a new immunoadsorption assay (IAA), were compared. The withinand between-run imprecision of the IAA (3.6-4.2% and 3.6-7.7%) was comparable with that of the WGA assay. The mean crossreactivity with liver ALP appeared to be 4% in the WGA assay and 11 % in the IAA. The reference ranges in a group of 155 healthy Caucasian (pre)pubertal schoolgirls were: 149-401 U/L (total ALP, 30 #{176}C), 105-349 U/L (bone ALP, 30 #{176}C, WGA assay), and 58-205 U/L (bone ALP, 25 #{176}C, IAA). Comparison of the WGA assay (x) with the IAA (y) demonstrated a correlation coefficient of 0.95 [Deming regression equation:y = (0.56 ± 0.01)x + (2.0 ± 1.5); S,,1= 5.3 UIL]. Correlation studies of the WGA assay and the IAA results with total ALP demonstrated r = 0.98 and 0.96, respectively.