Rationale, aims and objectives 39 Evidence-based medicine (EBM) holds
that estimates of effects of health interventions based on 40
high-certainty evidence (CoE) are expected to change less frequently
than the effects generated 41 in low CoE studies. However, this
foundational principle of EBM has never been empirically 42 tested. 43
Methods 44 We reviewed all systematic reviews and meta-analyses in
Cochrane Database of Systematic 45 Reviews from January 2016 through May
2021 (n=3,323). We identified 414(207x2) and 384 46 (192x2) pairs of
original and updated Cochrane reviews that assessed CoE and pooled 47
treatment effect estimates. We appraised CoE using the Grading of
Recommendations 48 Assessment, Development and Evaluation (GRADE)
method. We assessed the difference in 49 effect sizes between the
original versus updated reviews as a function of change in CoE, which 50
we report as a ratio of odds ratio (ROR). We compared ROR generated in
the studies that 51 changed CoE from very low/low (VL/L) to
moderate/high (M/H) vs. MH/H VL/L. We also 52 assessed the
heterogeneity and inconsistency (using the tau and I2 statistic), the
change in 53 precision of effect estimates (by calculating the ratio of
standard errors) (seR), and the absolute 54 deviation in estimates of
treatment effects (aROR). 55 Results 56 57 We found that CoE originally
appraised as VL/L had 2.1 (95%CI: 1.19 to 4.12; p=0.0091) times 58
higher odds to be changed in the future studies than M/H CoE. However,
the effect size was not 59 different when CoE changed from VL/L M/H vs.
M/H VL/L [ROR=1.02 (95%CI: 0.74 to 1.39) 60 vs. 1.02 (95%CI: 0.44
to 2.37); p=1 for the between subgroup differences]. aROR was similar
61 between the subgroups [median (IQR):1.12 (1.07 to 1.57) vs 1.21
(1.12 to 2.43)]. We observed 62 large inconsistency (I 2=99%) and
imprecision in treatment effects (seR=1.09). 63 Conclusions 64 We
provide the first empirical support for a foundational principle of EBM
showing that low65 quality evidence changes more often than high CoE.
However, the effect size was not different 66 between studies with low
vs high CoE. The finding that the effect size did not differ between low
67 and high CoE indicate urgent need to refine current EBM critical
appraisal methods
Empirical evaluation of fundamental principles of evidence-based medicine: a meta-epidemiological study
