Development of an in house ELISA for human intact osteocalcin and its utility in diagnosis and management of osteoporosis

Serum Osteocalcin (OC) is a biomarker for evaluating bone turnover in humans. Commercial kits of OC in India are imported, hence the associated high cost prohibits their use in routine screening of osteoporosis. The present study describes the development, validation of human OC ELISA and establishes cut off values for its use in screening and management of women at risk for osteoporosis. A sandwich OC ELISA was developed using immuno-reagents prepared indigenously and validated for analytical sensitivity, specificity, accuracy and compared with commercial kit using Bland-Altman method. The utility of OC assay was evaluated by ROC analysis. The new ELISA was sufficiently precise, accurate, matrix-free, sensitive and cost effective. The levels of OC were significantly different in women with osteopenia and osteoporosis (ANOVA, p 11.9 ng/mL for osteopenia and > 14.9 ng/mL for osteoporosis. The OC levels had maximum AUC of 0.831 in osteopenia and 0.932 in osteoporosis. Further, OC levels showed significant changes within 3 months in women monitored on therapy. The developed OC ELISA has great potential to be used as a biomarker for routine screening and management of osteoporosis in Indian women. •Developed ELISA is specific and sensitive to detect low levels of osteocalcin in Indian women•High predictive cut-off values of osteocalcin differentiate osteopenia and osteoporotic women•ROC curve analysis showed good sensitivity and specificity for both osteopenia and osteoporosis•Osteocalcin values can be an adjunct to BMD in diagnosis and management of osteoporosis