How Accurate is Your Sclerostin Measurement? Comparison Between Three Commercially Available Sclerostin ELISA Kits

Abstract

Sclerostin, bone formation antagonist is in the spotlight as a potential biomarker for diseases presenting with associated bone disorders such as chronic kidney disease (CDK-MBD). Accurate measurement of sclerostin is therefore important. Several immunoassays are available to measure sclerostin in serum and plasma. We compared the performance of three commercial ELISA kits. We measured sclerostin concentrations in serum and EDTA plasma obtained from healthy young (18–26 years) human subjects using kits from Biomedica, TECOmedical and from R&D Systems. The circulating sclerostin concentrations were systematically higher when measured with the Biomedica assay (serum: 35.5 ± 1.1 pmol/L; EDTA: 39.4 ± 2.0 pmol/L; mean ± SD) as compared with TECOmedical (serum: 21.8 ± 0.7 pmol/L; EDTA: 27.2 ± 1.3 pmol/L) and R&D Systems (serum: 7.6 ± 0.3 pmol/L; EDTA: 30.9 ± 1.5 pmol/L). We found a good correlation between the assay for EDTA plasma (r > 0.6; p < 0.001) while in serum, only measurements obtained using TECOmedical and R&D Systems assays correlated significantly (r = 0.78; p < 0.001). There was no correlation between matrices results when using the Biomedica kit (r = 0.20). The variability in values generated from Biomedica, R&D Systems and TECOmedical assays raises questions regarding the accuracy and specificity of the assays. Direct comparison of studies using different kits is not possible and great care should be given to measurement of sclerostin, with traceability of reagents. Standardization with appropriate material is required before different sclerostin assays can be introduced in clinical practice.

24-hour profile of serum sclerostin and its association with bone biomarkers in men

“…Previous reports of the correlations between sclerostin and other markers have been conflicting [21-28] and may reflect variations in the sclerostin assays utilized [29,30], differences in participant sex/age, timing of sampling, presence/absence of metabolic bone diseases, use of blood vs. mRNA sclerostin levels, and/or analytic variability. In addition, studies of pre- and post-menopausal women suggest race/ethnicity may affect BTM levels [31] and their associations with sclerostin [32].…”

“…48 h to obtain at least 2 full periods), the rigorous design employed (with individuals aligned for differences in phase that account for meals and sleep opportunities) should have been capable of detecting a sinusoidal rhythm in the 24-h study interval. In addition, given the variability in commercially available sclerostin assays [29,30], use of a different assay (i.e. one that does not detect fragments as this Biomedica sclerostin assay does) and/or sample type (e.g.…”

Hormonal and systemic regulation of sclerostin

“…Significant current limitations include our current understanding of natural biologic variables [including but not limited to the effects of age, sex, total body bone mineral content (BMC), circadian and seasonal variability; whether sclerostin fragments retain biologic activity; and the mechanism(s) by which sclerostin is cleared from the circulation] in addition to significant limitations associated with the performance characteristics of the current commercially available assays for sclerostin measurement (summarized in Table 1) [4–8]. …”

Biomarkers Predicting Bone Turnover in the Setting of CKD

“…The exact value of sclerostin as a biomarker of bone turnover remains yet to be established in particular in CKD patients not yet in dialysis. Unfortunately, an automated method for sclerostin measurement is currently lacking and commercially available ELISAs provide incongruent results [30,31].…”