Background Bone turnover markers (BTMs) are used in clinical practice for assessing patients with osteoporosis and their treatment. In Spain it is necessary to fine-tune the reference intervals, since they were established years ago in a low number of individuals.
Objectives The aims of this study were to establish robust reference intervals for BTMs in healthy young premenopausal Spanish women and to investigate the factors influencing BTMs.
Methods 185 women aged 35 to 45 yrs. from 13 centres in Catalonia were recruited. Blood and second void urine samples were collected between 8 and 10 a.m. after an overnight fast. Serum PINP and βCTX were measured by two automated methods (Elecsys, Rochea and IDS-ISYS, Immunodiagnostic Systemsb), bone ALP by ELISA (IDS, Vitro), osteocalcin by IRMA (Cis Bio) and urinary NTX by ELISA (Osteomark, Vitro). PTH and 25OHD levels were measured in all participants, who completed a questionnaire on lifestyle factors. A quantile regression was fit to estimate the 5%, 50% and 95% percentiles for the BMTs, and the Fisher's exact test and non-parametric tests were used to assess the influence of factors on BTMs.
Results The median (P5-P95) for BTMs were: Bone ALP 9.3 (6.0-13.8) ng/ml, PINPa 35.9 (20.8-60.6) ng/ml, PINPb 35.8 (20.8-64.9) ng/ml, NTX 32.7 (19.3-68.9) nM/mM, CTXa 0.250 (0.137-0.480) ng/ml, CTXb 0.246 (0.107-0.541), Osteocalcin 14.0 (8.0-23.0) ng/ml.
Oral contraceptive pills (OCPs) were reported in 10.9% of participants, mean BMI was 23 and 60% had 25OHD levels lower than 20 ng/ml. Women on OCPs had lower PINP levels (p=0.007).25OHD levels didn't influence BTMs, but low BMI was associated with higher levels of almost all BTMs.
Conclusions In conclusion, robust reference intervals for BTMs in a southern European country are provided.
Acknowledgements This study was funded by a research grant from de Societat Catalana de Reumatologia.
Disclosure of Interest None declared