Tartrate Resistant Acid Phosphatase (TRAcP) 5b is secreted exclusively by osteoclasts (cells responsible for resorbing bone). The level of TRAcP 5b in serum is therefore considered useful as a measure of osteoclast abundance and as an indirect indicator of bone resorption rate. Measurement of TRAcP 5b in serum is complicated due to the presence of a 10-fold higher concentration of TRAcP 5a, which is secreted by macrophages and dendritic cells. The two forms differ only in their glycosylation pattern and the removal of a 14 16 amino acid peptide from TRAcP 5b. Currently there is no automated immunoassay available for measurement of TRAcP 5b in human sera, so testing has been restricted to manual based assays. This work describes the initial performance assessment of the new IDS-iSYS TRAcP 5b (BoneTRAP®) assay. The TRAcP 5b assay developed on IDS-iSYS multi-discipline automated system has a measuring range from 0.5 to 14.0 U/L. The assay sensitivity is reported as limit of blank < 0.3 U/L; limit of detection: 0.5 U/L; and limit of quantitation ≤ 1.0 U/L. The total assay precision, as measured across 20 days is calculated as ≤ 12.0%. The assay shows a good correlation with Quidel MicroVue TRAP 5b assay yielding the following regression equation y (iSYS) =1.02x (Quidel) +0.18 with r2=0.95 (n=72). These results indicate the fully automated TRAcP 5b assay developed on the iSYS system is a sensitive and precise immunoassay. The first fully automated TRAcP 5b assay may provide a useful tool to assist in the diagnosis of osteoporosis and metabolic bone diseases including that associated with renal failure. Furthermore, the availability of a fully automated solution for detection of TRAcP 5b would simplify its measurement, increasing the potential for further research to be conducted into the involvement of TRAcP 5b in metabolic bone diseases.
Disclosure: The authors declared no competing interests.