Introduction: Osteoprotegerin (OPG) plays a protective role in bone remodelling as it provides a ‘decoy’ binding site for RANKL, preventing the stimulation of osteoclasts. Autoantibodies to OPG allow a sustained reaction between RANKL and RANK which in turn increase bone degradation. Autoantibodies against Osteoprotegerin (-OPGAb) first isolated in patients with autoimmune conditions associated with high bone turnover have been shown to be present in 14% of a healthy young adult population. Bone degradation is more prominent in the oldest population, particularly in women. Objective: To define a reference range for OPG autoantibodies in non-osteoporotic post-menopausal women. Method: Using a previously developed sandwich ELISA assay we were able to detect OPG autoantibody in serum samples taken from non-osteoporotic post-menopausal women (ANSAVID study - 60-65yrs). Briefly, -OPGAb are captured by the use of an immobilized full-length human recombinant OPG and detected by the sequential addition of a biotinylated antibody and a horseradish-peroxidase-labelled streptavidin. The concentration of human α-OPGAb in the samples is determined directly from a 4PL-fit standard curve. Results: We established that the population of post-menopausal women who do not present osteoporosis do not have elevated concentration of -OPGAb as compared to a younger healthy population (17-32yrs). This suggest that -OPGAb is not normally occurring with age suggesting that the production of -OPGAb is solely related to pathologic conditions in which the bone is heavily degraded. Conclusion: Comparison of osteoporotic patient samples to the non-osteoporotic post-menopausal women would be interesting to determine whether -OPGAb can be used to identify appropriate treatment options for this particular subgroup of patients
