Both authors independently assessed the risk of bias of each included study and extracted outcome data (from published study information) for assessment of bone mineralization, growth and nutritional status, frequency of
vitamin D deficiency, respiratory status, quality of life and adverse events.
MAIN RESULTS: Six studies (239 participants) are included, although only three studies provided data from 69 adults and children with
cystic fibrosis for analysis. One study compared a single high dose of
vitamin D (250,000 IU) to placebo at the time of hospital admission with a respiratory exacerbation in 30 pancreatic insufficient adults with
cystic fibrosis. The second study compared supplemental 800 international units (IU)
vitamin D and placebo for 12 months in 30 osteopenic pancreatic insufficient adults; both groups continued 900 IU
vitamin D daily. The third study compared supplemental 1 g
calcium alone, 1600 IU
vitamin D alone, 1600 IU
vitamin D and 1 g
calcium and placebo in a double-blind randomised cross-over study; only nine children who completed both
vitamin D and placebo groups after six-months supplementation and a three-month washout period are included; pancreatic sufficiency or disease status of participants are not defined. The studies are not directly comparable due to differences in supplementation, outcome reporting and possibly participant characteristics (e.g. severity of
lung disease, growth and nutrition, pancreatic sufficiency).The only outcome for which we could combine data from more than two studies was
25-hydroxyvitamin D levels; patients receiving
vitamin D supplementation had significantly higher levels, mean difference 7.24 ng/ml (95% confidence interval 5.01 to 9.46). However, ironically one study reported 1,25(
OH)2D with levels significantly favouring the placebo group, mean difference -30.30 pmol/ml (95% confidence interval -59.89 to -0.71). Bone mineral density was measured in two studies; both described no significant change between groups. There were no adverse events in any study.The remaining three studies are published as abstracts only and did not provide data for analysis. These abstracts include: a report of pre-intervention data in a study comparing daily
calcitriol (0.25 or 0.5 micrograms) with placebo in pancreatic insufficient children and young adults; an interim report of a double-blind randomised control study comparing 5000 IU
vitamin D daily for 12 weeks during winter in 67 adult
cystic fibrosis patients; and a comparison of the effect of three months of
vitamin D supplementation (dose not specified) with placebo on bone mineral density in 42 children with
cystic fibrosis and
low bone mineral density.Risk of bias was highly variable between all studies. Only one study had a low risk of bias for the five main criteria (random sequence generation, allocation, blinding, attrition and reporting). The rest of the studies had unclear or high risks of bias. Two studies had a low risk of bias for blinding and another two studies for attrition bias. In the studies published as abstracts, assessment of the risks of bias was uncertain in many aspects.
AUTHORS' CONCLUSIONS: