An analysis of randomized controlled trials on anal fistula conducted between 2000 and 2020 based on the Fragility Index and Reverse Fragility Index

Abstract

Aim: The aim of this work was to evaluate the robustness of randomized controlled trials (RCTs) on anal fistula management using the news tools of Fragility Index (FI), Reverse Fragility Index (RFI) and their corresponding fragility quotients.

Method: A systematic search was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines which utilized MEDLINE, EMBASE, Cochrane Library and Web of Science databases. Inclusion criteria included RCTs related to the management of anal fistula published from 2000 to 2022 with dichotomous outcomes measures and 1:1 allocation. Calculation of FI and RFI was performed by creating 2 × 2 contingency tables by successively changing one nonevent to an event for each outcome measure until the result was made nonsignificant or significant, respectively. The Fragility Quotients were calculated by dividing the FI or RFI by the total sample size. Fragile results were defined as those with a FI or RFI equal to or less than the number of patients lost to follow-up. Additionally, those with a FI or RFI less than 3 were also considered fragile. Studies were considered extremely fragile if FI was ≤1 or FQ was ≤0.01.

Results: There were 36 RCTs that met our criteria, with 3223 patients. Among these, 19 (53%) were positive RCTs (p < 0.005) and 17 (47%) were negative RCTs (p > 0.05). The median FI was 2 (0-5). The analysis by categorical subgroup showed a strong correlation between FI and the p-value (p = 0.000) and the number of events (p = 0.011). The median RFI was 5 (3.5-9.5) and the subgroup analysis showed a strong correlation between RFI and the p-value (p = 0.000), sample size (0.021) and number needed to treat/number needed to harm (0.000). We considered 63.2% of positive RCTs to be fragile and 35.3% of negative RCTs.

Conclusions: In the present study we demonstrated the lack of robustness of study findings in published RCTs in the field of anal fistula.

Keywords: anal fistula; fragility index; reverse fragility index.