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Paediatric surgical trials, their fragility index, and why to avoid using it to evaluate results
Arne Schröder1, Oliver J Muensterer2,3, Christina Oetzmann von Sochaczewski4,5
1Klinik für Kinder- und Jugendmedizin, Klinikum Dortmund, Dortmund, Germany.
Insights
Paediatric surgical trials have low fragility indices, suggesting results may not be robust. Researchers should avoid using the fragility index in this field due to its limitations, especially for smaller studies.
Area of Science:
- Clinical research methodology
- Paediatric surgery
Background:
- The fragility index is increasingly used to assess comparative clinical studies.
- There is no standardized definition or consensus on fragility index calculation.
- This study evaluates the fragility index in paediatric surgical trials.
Purpose of the Study:
- To calculate and analyze the fragility index and its permutations in paediatric surgical trials.
- To determine the correlation between fragility indices and P values.
- To assess the utility and limitations of the fragility index in this specific population.
Main Methods:
- Searched PubMed for prospective paediatric surgical trials with intervention and control groups.
- Calculated fragility indices, reverse fragility indices, and fragility quotients.
- Analyzed relationships using Spearman's rank correlation and calculated S values.
Main Results:
- 87 trials were included; median fragility index was 1.5, and median reverse fragility index was 3.
- Fragility indices were strongly inversely correlated with P values (ρ = -0.71).
- Reverse fragility indices were moderately correlated with P values (ρ = 0.5).
Conclusions:
- Paediatric surgical trials exhibit low fragility indices and reverse fragility indices.
- The fragility index is a transformed P value with significant limitations, penalizing small studies.
- The fragility index is not recommended for paediatric surgery due to its detrimental impact on small study evaluation.
Background:
The fragility index has been gaining ground in the evaluation of comparative clinical studies. Many scientists evaluated trials in their fields and deemed them to be fragile, although there is no consensus on the definition of fragility. We aimed to calculate the fragility index and its permutations for paediatric surgical trials.
Methods:
We searched pubmed for prospectively conducted paediatric surgical trials with intervention and control group without limitations and calculated their (reverse) fragility indices and respective quotients along with posthoc-power. Relationships between variables were evaluated using Spearman's ρ. We also calculated S values by negative log transformation base-2 of P values.
Results:
Of 516 retrieved records, we included 87. The median fragility index was 1.5 (interquartile range: 0-4) and the median reverse fragility index was 3 (interquartile range: 2-4), although they were statistically not different (Mood's test: χ2 = 0.557, df = 1, P = 0.4556). P values and fragility indices were strongly inversely correlated (ρ = - 0.71, 95% confidence interval: - 0.53 to - 0.85, P < 0.0001), while reverse fragility indices were moderately correlated to P values (ρ = 0.5, 95% confidence interval: 0.37-0.62, P < 0.0001). A fragility index of 1 resulted from P values between 0.039 and 0.003, which resulted in S values between 4 and 8.
Conclusions:
Fragility indices, reverse fragility indices, and their respective fragility quotients of paediatric surgical trials are low. The fragility index can be viewed as no more than a transformed P value with even more substantial limitations. Its inherent penalisation of small studies irrespective of their clinical relevance is particularly harmful for paediatric surgery. Consequently, the fragility index should be avoided.
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