Table 2 Assessment of risk of bias in included studies
From: Vitamin D supplementation in children with asthma: a systematic review and meta-analysis
Study name | Random sequence generation | Allocation concealment | Blinding | Intention to treat analysis | Completeness of data | Selective outcome reporting | Early stoppage of trial |
|---|---|---|---|---|---|---|---|
Majak, [ 16 ] 2009 | Low risk. “Patients were randomized according to a computer-generated stratified allocation schedule for intervention” | Unclear risk | Low risk. | Unclear risk. | Data for 2 patients (5%) missing | Low risk. | Low risk |
Probably patients, providers, data collectors and outcome assessors were blinded given the use of placebo | In the intent-to-treat analysis population excluded patients who received intervention for less than 2 months. Number of those excluded not reported | All outcomes listed in the trial registry and in the methods section are reported in the results section | Not stopped early for benefit | ||||
Lewis, [ 18 ] 2012 | Unclear risk | Unclear risk | Unclear risk | Unclear risk | High risk | Low risk | Low risk |
No details reported | No details reported | Probably no one blinded | No details reported | data for 15 patients (33.3%) missing | No published protocol but outcomes listed in the methods section are reported in the results section. | Not stopped early for benefit. | |
Schou, [ 14 ] 2003 | Low risk | Unclear risk | Low risk. | Unclear | Missing data: 2 | Low risk | Low risk |
“Treatment order was allocated by means of a computerized randomization scheme”. | No details reported | Probably patients, providers, data collectors and outcome assessors were blinded given the use of placebo | No details reported | patients (11,7%). | No published protocol but outcomes listed in the methods section are reported in the results section. | Not stopped early for benefit. | |
Majak, [ 17 ] 2011 | Low risk. | Unclear | Low risk. | Unclear | Low risk. | Low risk | Low risk |
“Patients were randomized according to a computer-generated allocation schedule.” | No details reported | Probably patients, providers, data collectors and outcome assessors were blinded given the use of placebo | No details reported | No missing data. | No published protocol but outcomes listed in the methods section are reported in the results section. | Not stopped early for benefit |