Meta-analysis: vitamin D compounds in chronic kidney disease.

Vitamin D compounds are widely used to prevent and treat secondary hyperparathyroidism. To determine whether vitamin D therapy improves biochemical markers of mineral metabolism and cardiovascular and mortality outcomes in chronic kidney disease. MEDLINE (January 1966 to July 2007), EMBASE (January 1980 to July 2007), and Cochrane databases were searched without language restriction. Randomized, controlled trials of vitamin D compounds in chronic kidney disease were identified. Two authors independently extracted data. Seventy-six trials were identified for inclusion; 3667 participants were enrolled. Vitamin D compounds did not reduce the risk for death, bone pain, vascular calcification, or parathyroidectomy. Compared with placebo, established vitamin D sterols were associated with an increased risk for hypercalcemia (relative risk, 2.37 [95% CI, 1.16 to 4.85]) and hyperphosphatemia (relative risk, 1.77 [CI, 1.15 to 2.74]) but did not show a consistent reduction in parathyroid hormone (PTH) levels. Compared with placebo, more recently developed vitamin D analogues were associated with hypercalcemia (relative risk, 5.15 [CI, 1.06 to 24.97]) but not hyperphosphatemia, and levels of PTH were reduced (weighted mean difference, -10.77 pmol/L [CI, -20.51 to -1.03 pmol/L]). For suppression of PTH, intravenous administration was superior to oral vitamin D, but higher intravenous doses were used. Few studies reported patient-level outcomes, including mortality (8 of 76 trials), and only 5 trials directly compared the effects of treatment with newer vitamin D compounds versus established ones. Heterogeneity in some comparisons remained unexplained by metaregression analyses. Vitamin D compounds do not consistently reduce PTH levels, and beneficial effects on patient-level outcomes are unproven. The value of vitamin D treatment for people with chronic kidney disease remains uncertain.