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Fragility Index in Cardiovascular Randomized Controlled Trials

Muhammad Shahzeb Khan1, Rohan Kumar Ochani2, Asim Shaikh2

  • 1Department of Internal Medicine, John H. Stroger Jr. Hospital of Cook County, Chicago, IL (M.S.K., N.Y.).

Circulation. Cardiovascular Quality and Outcomes
|December 12, 2019
PubMed

Insights

The fragility index (FI) assesses the robustness of cardiovascular randomized controlled trials (RCTs). Many trials show low FI, indicating results may not be robust, especially when patient follow-up is incomplete.

Area of Science:

  • Clinical Trials
  • Cardiovascular Medicine
  • Biostatistics

Background:

  • Traditional measures like P values and effect sizes are not always intuitive for clinicians.
  • The fragility index (FI) offers a more interpretable metric for binary outcomes.
  • FI quantifies the minimum patient number shift needed to negate a statistically significant finding.

Purpose of the Study:

  • To evaluate the robustness of cardiovascular randomized controlled trials (RCTs) using the fragility index (FI).
  • To assess the reliability of statistically significant primary outcomes in cardiovascular research.

Main Methods:

  • Retrospective analysis of cardiovascular RCTs published between 2007-2017 in six high-impact journals.
  • Inclusion criteria: sample size >500, factorial or dichotomous primary outcomes.
  • Calculation of FI for each selected trial.

Main Results:

  • Median FI was 13 among 123 included RCTs.
  • 22.8% of trials had an FI of 1-4, and 30.1% had more patients lost to follow-up than their FI.
  • Pharmaceutical interventions (median FI=19) and multiregional RCTs (median FI=22) showed higher FI.
  • FI varied significantly by subspecialty (P=0.020).

Conclusions:

  • Significant variation in FI exists across cardiovascular trials.
  • Results emphasize the need for cautious interpretation of trial outcomes.
  • Particular attention is warranted when the number of patients lost to follow-up surpasses the trial's FI.
Abstract

Keywords:
biascardiovascular systemfragility indexheart failuresample size

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