• Mandy Rickard, Armando J Lorenzo, Jessica H Hannick, Anne-Sophie Blais, Martin A Koyle, and Darius J Bägli.
• Division of Urology, Hospital for Sick Children and Department of Surgery, University of Toronto, Toronto, Ontario, Canada. Electronic address: mandy.rickard@sickkids.ca.
• Urology. 2019 Nov 1; 133: 204-210.

ObjectiveTo review the robustness of hydronephrosis literature with the application of fragility index (FI) and fragility quotient (FQ) calculations.MethodsA literature review was conducted using Pubmed, Medline, and Ovid for "hydronephrosis" and associated terms and we included all studies with at least 2 groups being compared. FI was calculated by populating study results into a 2-by-2 contingency table and generating a P value using Fisher's exact test. Next, events were manually added to the group with the fewest events, while removing a nonevent from the same group and Fisher's exact test repeated until the P value was >.05. FQ was calculated by dividing FI by the total sample size.ResultsThe 130 included articles were published between 1986 and 2018 in 32 journals. Median citation count was 14 (0-252), 30% were RCTs and most papers originated in the United States (28%), Turkey(10%), and Canada(9%). Median FI was 2 (1-112), FQ was 0.023 (0.0010-0.55), and 60 papers (46%) had a FI of 1, indicating extremely fragile results. There was a significant difference in the FI between observational studies and RCTs (10 ± 17 vs 4 ± 5; P = .02); however, there was no difference in FQ (0.032 ± 0.030 vs 0.053 ± 0.080; P = .09) between them.ConclusionNearly half of studies in hydronephrosis literature reporting significant results are extremely fragile, requiring addition of only a couple of events in 1 treatment arm to significantly modify the results. As such, objective reporting of robustness of results should include FI and FQ which may help diminish over-reliance on P values as the main indicator of clinical significance in comparative studies.Copyright © 2019 Elsevier Inc. All rights reserved.

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