A new study published in The Spine Journal reviews evidence-based orthopedics studies, identifying all randomized controlled trials that reported at least one positive outcome.
The researchers used Fisher's exact test to compute the Fragility Index values and multivariable linear regression for associated factors.
There were 40 eligible randomized controlled trials with the average sample size of 132 patients and the average total chosen outcome events of 31. Here are five things to know from the report:
1. The average Fragility Index was two, indicating that adding two events to one of the trial's treatment arms would eliminate the statistical significance.
2. In 75 percent of the trials, the Fragility Index was less than or equal to three events.
3. In 65 percent of the trials, the Fragility Index was less than or equal to the number of patients lost to follow-up.
4. There was a positive correlation between the Fragility Index values and the total sample size.
5. Increasing Fragility Index values were associated only with increasingly significant reported p-values when the researchers adjusted for losses to follow-up and risk of bias.
"The addition of only a small number of outcome events can completely eliminate significance," concluded the study authors. "Surgeons, researchers and other evidence users should exercise caution when interpreting the findings from RCTs with low Fragility Index values and applying these results to patient care."