The prevalence and risk of missing outcome data in prenatal vitamin D supplemented gestational diabetes mellitus patients: a systematic review and meta-analysis protocol
Authors: Saha Sumanta 
Published: October 2020

Background: Missing outcome data in clinical trials are important determinants of internal validity; however, its burden and risk in gestational diabetes mellitus (GDM) mothers supplemented with vitamin D remain poorly studied. Therefore, a systematic review and meta-analysis protocol is proposed here to study it. 
Methods: The English language publications, irrespective of its publication date, will be searched in electronic databases for randomized controlled trials studying the above outcome. The eligible trials will undergo the risk of bias assessment by the Cochrane tool. Data on its trial design, population characteristics, interventions compared, and the outcome will be abstracted. The prevalence and incidence (in risk ratio) of missing outcome data will be estimated meta-analytically. The statistical heterogeneity assessment will include the use of Chi2 and I2 statistics. For the explanation of any substantial heterogeneity, a meta-regression analysis will ensue. The statistical significance will be determined at P <0.05 and 95% CI. All analyses will be done in Stata statistical software. If the quantitative analysis is not possible, narrative reporting will happen.
Results: The reporting of the review will follow the PRISMA guideline. Statistically significant pairwise meta-analysis finding's grading will occur by the GRADE approach.
Conclusion: The proposed review will estimate the prevalence of missing outcome data in vitamin D supplemented GDM mothers in clinical trials and compare its risk with the placebo recipients.
PROSPERO registration ID: CRD42020180634
 
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