Validation of a novel, rapid, high precision sclerostin assay not confounded by sclerostin fragments

Sclerostin is a 190 amino acid protein secreted primarily by osteocytes. It was initially identified due to mutations in the SOST gene associated with high bone mass phenotypes. Much recent work has sought to determine the importance of sclerostin across an array of conditions which affect the human skeleton. However, accurate measurement of sclerostin from serum and plasma sources remains a significant impediment, with currently available commercial assays showing marked differences in measured sclerostin values. Accordingly, sclerostin assay standardization remains an important but unmet need before sclerostin measurements can be used for the clinical management of bone disease. Here we characterize a novel automated chemiluminescent sclerostin assay (LIAISON®, DiaSorin) which overcomes many of these limitations. Important assay characteristics include: a wide dynamic range (50-6500 pg/mL); high intra- (<2.5%) and inter- (<5%) assay precision; matched serum and plasma equivalence (<10% difference); specificity for the intact sclerostin molecule; and rapid assay results. Serum sclerostin levels measured with the LIAISON® assay in a population-based sample of adult men (n = 278) and women (n = 348) demonstrated that sclerostin levels were significantly higher in men as compared to women and were positively associated with age in both sexes, consistent with previously published work. In postmenopausal women, serum sclerostin levels measured with the LIAISON® assay were reduced in response to treatment with either estrogen or teriparatide, again consistent with previous findings. Collectively, the above data demonstrate that the LIAISON® sclerostin assay provides a reliable tool for more confident assessment of emergent mechanisms wherein sclerostin may impact a number of bone related pathologies.