PSM retrospective 110 patients, 55 treated with high-dose IV vitamin C, showing lower progression to severe disease with treatment. Patients in each group were in different time periods, time based confounding is likely due to SOC improving over time. ChiCTR2000033050.
Zhao et al., 4/22/2021, retrospective, propensity score matching, China, Asia, peer-reviewed, 15 authors.
risk of disease progression, 72.0% lower, RR 0.28, p = 0.03, treatment 4 of 55 (7.3%), control 12 of 55 (21.8%), adjusted per study, PSM.
time to viral-, 7.7% higher, relative time 1.08, p = 0.79, treatment 55, control 55, PSM.
This study is excluded in the after exclusion results of meta analysis: substantial time varying confounding likely due to declining usage over the early period when overall treatment protocols improved dramatically.
Effect extraction follows pre-specified rules
prioritizing more serious outcomes. For an individual study the most serious
outcome may have a smaller number of events and lower statistical signficance,
however this provides the strongest evidence for the most serious outcomes
when combining the results of many trials.