Parathyroid hormone variability parameters for identifying high turnover osteodystrophy disease in hemodialysis patients: an observational retrospective cohort study.

Abnormalities in bone morphology that develop secondary to chronic kidney disease are defined as renal osteodystrophy and are identified by bone biopsy. As systematic and sequential bone biopsy is not practicable on a large number of patients, various chemical bone markers are commonly used to detect the bone remodeling status in chronic kidney disease and to grade bone disease in the clinical setting. Recent literature has considered the effect of absolute levels of parathyroid hormone (PTH) on clinical outcomes and not the measurement of their change over time, the PTH variability. In a retrospective observational study, we examined PTH variability parameters in a group of hemodialysis patients as independent risk factors for high vs. low turnover osteopathy, and investigated their usefulness with respect to commonly used markers of renal osteodystrophy. The study was conducted on 90 chronic hemodialysis patients undergoing regular treatment at the same dialysis centre (Catanzaro, Italy) with standard bicarbonate dialysis. Patients were classified into either high or medium-low turnover osteopathy for the diagnosis based on renal osteodystrophy using the following criteria: PTH ≥ 400 pg/mL associated with bone ALP ≥ 20 ng/mL. We used a regression-based measurement of PTH variability, which was characterized by different parameters: PTH-Res-SD, PTH-Slope, PTH-Intercept, PTH-Abs-Var, and PTH-Res-SD. In our analysis, these parameters of PTH variability were demonstrated to be good independent predictive factors for high turnover osteodystrophy, and they had a greater sensitivity than the use of a single and/or mean PTH measurements in renal osteodystrophy classification.