Background: Secondary hyperparathyroidism is a frequent complication of chronic kidney disease (CKD). The goal of treatment is to achieve circulating levels of parathyroid hormone (PTH) associated without oversuppression of bone turnover. This is commonly achieved by treatment with vitamin D analogs. Doses of vitamin D compounds are usually monitored by measurement of circulating levels of PTH.
Study design: To prospectively assess the effects on bone histology of two different protocols for dosing vitamin D.
Setting and participants: African-American patients from the same geographic area, managed by the same team of physicians in three dialysis clinics were studied. Patients were treated with vitamin D for 3 years and underwent bone biopsies for assessment of bone turnover. Dosing of vitamin D during the 3 years prior to the biopsy was done following two different guidelines. One group was treated following K/DOQI guidelines adapted to the bio-intact PTH assay (Protocol A), the other group was managed (Protocol B) following K/DOQI guidelines for intact PTH and/or the ratio of PTH-(1-84)/N-terminally truncated fragments (PTH ratio).
Predictor: Levels of circulating PTH and/or PTH ratio.
Outcome: Prevalence of low bone turnover.
Measurements: Qualitative and quantitative assessment of bone histology after tetracycline labeling.
Results: 7 out of 22 patients managed following Protocol A were found to have low bone turnover (32%) by bone histology. None of the 21 patients managed by Protocol B for guidance of vitamin D therapy, had low bone turnover.
Limitations: Lack of bone biopsy at the beginning of study.
Conclusions: This report indicates that the additional information provided by the PTH ratio represents a distinct advantage in avoiding low bone turnover over the use of a single PTH assay to guide vitamin D dosing in African-American patients with CKD Stage 5 on dialysis.