Conclusion
Sclerostin levels are markedly different according to the immunoassay used. Detection of an association with calcitropic hormones or turnover markers relies on the epitope recognized by the immunoassay and adjustment for bone mass.
Objective
We assessed the association between serum sclerostin and calcitropic hormones, bone turnover marker levels, bone mineral content/density, and microstructure using 3 different immunoassays. Design, setting, and participants: In a cross-sectional study, serum sclerostin was measured in a cohort of 187 healthy subjects (98 women; 89 men) aged 65 ± 1 (±SD) years.
Results
Overall, mean sclerostin (95% confidence interval) was 37.3 (18.0-69.2) ng/L, 1165.8 (464.0-2296.4) ng/L, and 513.5 (250.7-950.9) ng/L with assays I, II, and III, respectively. Serum sclerostin was higher in men with assays II and III. In all 3 assays, sclerostin and PTH were inversely correlated, only after adjustment for whole-body bone mineral content (WB-BMC). After adjustment for sex and WB-BMC, the bone turnover markers amino-terminal propeptide of type I procollagen and carboxyterminal cross-linked telopeptide of type I collagen negatively correlated only with assay II. In all 3 assays, sclerostin positively correlated to WB-BMC, the distal radius and the distal tibia cortical area, cancellous bone volume and trabecular number, and lumbar spine and proximal femur areal bone mineral density after adjustment for sex.