CHARACTERISTICS OF A 2-SITE IMMUNORADIOMETRIC ASSAY FOR HUMAN SKELETAL ALKALINE-PHOSPHATASE IN SERUM

This two-site IRMA includes specific monoclonal antibodies for measuri ng skeletal alkaline phosphatase (B-ALP) in human serum. Assay calibra tion is based on mass units (micrograms per liter) and was established with purified B-ALP from a human osteosarcoma cell line, SAOS-2. Prec ision studies demonstrated intra- and interassay CVs of 3-5% and 5-7%, respectively. Relative reactivity studies showed that the assay has a sevenfold preference for detecting B-ALP compared with the liver isoe nzyme in serum. The normal reference interval for 478 healthy adults w as 5-22 mu g/L. Method comparison studies showed good correlation betw een this B-ALP assay (y) and commercially available electrophoretic me thods (x) (y = 0.3540x + 20.5, R(2) = 0.929) in a pagetic population. Temporal profiles for total ALP, this IRMA B-ALP assay, and B-ALP by e lectrophoresis in three pagetic patients were parallel. We conclude th at this assay demonstrates good analytical performance and would be us eful for the clinical assessment of metabolic bone disorders.