Analysis of indications for selectively missing results in comparative registry-based studies in medicine: a meta-research study.

Background: We assess if there are indications that results of registry-based studies comparing the effectiveness of interventions might be selectively missing depending on the statistical significance (p < 0.05).

Methods: Eligibility criteria Sample of cohort type studies that used data from a patient registry, compared two study arms for assessing a medical intervention, and reported an effect for a binary outcome. Information sources We searched PubMed to identify registries in seven different medical specialties in 2022/23. Subsequently, we included all studies that satisfied the eligibility criteria for each of the identified registries and collected p-values from these studies. Synthesis of results We plotted the cumulative distribution of p-values and a histogram of absolute z-scores for visual inspection of selectively missing results because of p-hacking, selective reporting, or publication bias. In addition, we tested for publication bias by applying a caliper test.

Results: Included studies Sample of 150 registry-based cohort type studies. Synthesis of results The cumulative distribution of p-values displays an abrupt, heavy increase just below the significance threshold of 0.05 while the distribution above the threshold shows a slow, gradual increase. The p-value of the caliper test with a 10% caliper was 0.011 (k = 2, N = 13).

Conclusions: We found that the results of registry-based studies might be selectively missing. Results from registry-based studies comparing medical interventions should be interpreted very cautiously, as positive findings could be a result from p-hacking, publication bias, or selective reporting. Prospective registration of such studies is necessary and should be made mandatory both in regulatory contexts and for publication in journals. Further research is needed to determine the main reasons for selectively missing results to support the development and implementation of more specific methods for preventing selectively missing results.