METHODS: We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) of vitamin C versus comparative interventions in patients with COVID-19. The outcome of interest was all-cause mortality.

RESULTS: The meta-analysis of eleven trials using a random-effects model revealed significant reduction in the risk of all-cause mortality with the administration of vitamin C among patients with COVID-19 relative to no vitamin C (pooled odds ratio = 0.53; 95% confidence interval 0.30-0.92). Subgroup analysis of studies that included patients with severe COVID-19 also produced findings of significant mortality reduction with the administration of vitamin C relative to no vitamin C (pooled odds ratio = 0.47; 95% confidence interval 0.26-0.84).

METHODS: We examined CPGs and UpToDate point-of-care resources on the management of critically ill COVID-19 patients that had been published as of 30 April 2020 and compared them against the CPG by the WHO. The main outcome was the rate of consistency among CPGs for the management of critically ill COVID-19 patients. Sensitivity analyses were conducted by excluding recommendation statements that were described as insufficient evidence and by excluding single CPGs one at a time.

RESULTS: Thirteen reference recommendations derived from the CPG of the WHO were generated using discrete and unambiguous specifications of the population, intervention, and comparison states. Across CPGs, the rate of consistency in direction with the WHO is 7.7%. When insufficient evidence codings were excluded, the rate of consistency increased substantially to 61.5%. The results of a leave-one-out sensitivity analysis suggested that the UpToDate recommendation source could explain the inconsistency. Consistency in direction rates changed by an absolute 23.1% (from 1/13 (7.7%) to 4/13 (30.8%)) if UpToDate was removed.