The ratio of effect size (effect sizes pooled from studies with ITB relative to those pooled from studies without ITB) was 0.71 (95% CI, 0.66-0.78), suggesting that the effect sizes from studies with ITB were exaggerated by an average of 29% in favor of the intervention/exposure.

Given the projected high prevalence and nontrivial influence of ITB, ITB should be considered in studies with survival analyses, and improving reporting standards by researchers as well as collective surveillance from readers, reviewers, and editors is warranted. Future studies should address how ITS may also interact with other trial characteristics and biases in affecting treatment effect estimates.

In a comparison of overall summary results with vs without #ImmortalTimeBias (ITB) in 12 systematic reviews addressing 21 clinical topics, evidence reversal occurred in 5 (23.8%), where results changed from statistically significant to not (or vice versa) after excluding studies with ITB
#biostats