Assessment of urinary bone markers for monitoring treatment of osteoporosis.

Background: The usefulness of urinary markers of bone turnover in monitoring therapy depends on their within-person variability compared with their responses to therapy. The aim of this study was to assess the performance of two such markers on this basis.

Methods: We measured variation, during a whole year, of cross-linked N-terminal telopeptide of collagen I (NTx) and urinary deoxypyridinoline (DPD) as ratios to creatinine concentration and after log-transformation of the ratios in untreated women stratified into three bone density classes, of which the lowest was osteoporotic.