Background Biochemical markers of bone turnover levels have been suggested as predictors of long-term response in bone mass density (BMD) to teriparatide. However, its usefulness in clinical practice is unknown.
Objectives To identify the patients that will have significant increases in BMD after teriparatide using osteocalcin (OC) levels.
Methods Prospective observational study was performed. OC was measured at baseline, 3 months (M) and 18 M and BMD at baseline and 18 M (LUNAR Expert 1320R). Correlation between OC levels and BMD changes was evaluated by Spearman rank correlation analysis. Discriminant cut-off values for OC (baseline and 3M changes) in predicting “threshold” BMD increases >15% were determined using receiver operating characteristics curve (ROC). Kappa coefficient was calculated to identify the agreement between patients identified as good responders by their OC levels.
Results 57 patients (91.2% female) with mean age of 67.65±8.8 years were included. After treatment, median BMD change in lumbar spine (LS) was 0.088 g/cm2 (10.65%). Median baseline OC level was 18.9 ng/mL [4.2 – 71.3] and median 3M OC change was 27.5 ng/mL [0.30 – 93.50].
LS BMD gains after treatment correlated significantly with baseline OC (r=0.324; p=0.036) as well with 3M OC changes (r=0.336; p=0.049). Baseline OC and 3M OC changes showed a good accuracy in predicting >15% LS BMD change (area under the curve AUC 0.694, p=0.03 and AUC 0.748, p=0.017, respectively). Baseline OC of 26.75 ng/mL predict 15% improvement in BMD with sensitivity (S) 40%, specificity (E) 92.6%, positive predictive value (PPV) 74.84%, negative predictive value (NPV) 74%, positive likelihood ratio (LR) 5.4 and negative LR 0.65. 39.3 ng/mL in 3M OC changes predict 15% improvement in BMD with: S 50%, E 91.3%, PPV 74.89%, NPV 41.67%, positive LR 5.74 and negative LR 0.55. We found a good agreement (Kappa 0.697; p=0.01) between patients identified as good responders (baseline OC ≥26.75 ng/mL and 3M OC changes≥39.3 ng/mL).
Conclusions 26.75 ng/mL in baseline OC and 39.3 ng/mL increases in OC were the most convenient predictors of BMD response in clinical practice. These values can be used either to select patients (that will probably have good results) as well for assessing adherence and treatment response at 3 months.
Disclosure of Interest None declared
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