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An internal pilot study for a randomized trial aimed at evaluating the effectiveness of iron interventions in
Kawsari Abdullah1,2, Kevin E Thorpe3,4, Eva Mamak5
1Division of Pediatric Medicine, Department of Pediatrics, Pediatrics Outcomes Research Team, The Hospital for Sick Children, Room 109708, 10th Floor, 555 University Avenue, M5G 1X8, Toronto, ON, Canada. kawsari.abdullah@sickkids.ca.
Insights
This pilot study refined sample size calculations for the OptEC trial, evaluating oral iron for children with non-anemic iron deficiency. Results informed strategies to improve adherence and trial design.
Area of Science:
- Pediatric Nutrition
- Clinical Trial Design
- Iron Deficiency
Background:
- The OptEC trial investigates oral iron effectiveness in young children with non-anemic iron deficiency (NAID).
- Initial sample size calculations had uncertainties, necessitating an internal pilot study.
- Pilot study objectives included parameter estimation for sample size recalculation and adherence assessment.
Purpose of the Study:
- To obtain reliable estimates of standard deviation and design factor for the Early Learning Composite (ELC) outcome.
- To recalculate the sample size for the main OptEC trial.
- To assess adherence rates and identify reasons for non-adherence in the pilot study population.
Main Methods:
- The first 30 subjects of the OptEC trial participated in the internal pilot study.
- Standard deviation of the 4-month follow-up ELC scores was estimated by pooling group-specific SDs.
- Sample size was recalculated using ANCOVA, incorporating the design factor (1-ρ²), and adherence was parent-reported.
Main Results:
- The estimated standard deviation (S2) for the ELC was 17.40, and the design factor (1-ρ²) was 0.21.
- The recalculated sample size ranged from 32-56 subjects (16-28 per group) for 80% power at 5% significance.
- Adherence varied widely (14%-100%), with 44% of children achieving ≥86% adherence.
Conclusions:
- Pilot study data provided updated parameters for the definitive OptEC trial design.
- The recalculated sample size is smaller and more precise.
- Strategies to enhance adherence were identified and will be implemented in the full trial.
Background:
The OptEC trial aims to evaluate the effectiveness of oral iron in young children with non-anemic iron deficiency (NAID). The initial sample size calculated for the OptEC trial ranged from 112-198 subjects. Given the uncertainty regarding the parameters used to calculate the sample, an internal pilot study was conducted. The objectives of this internal pilot study were to obtain reliable estimate of parameters (standard deviation and design factor) to recalculate the sample size and to assess the adherence rate and reasons for non-adherence in children enrolled in the pilot study.
Methods:
The first 30 subjects enrolled into the OptEC trial constituted the internal pilot study. The primary outcome of the OptEC trial is the Early Learning Composite (ELC). For estimation of the SD of the ELC, descriptive statistics of the 4 month follow-up ELC scores were assessed within each intervention group. The observed SD within each group was then pooled to obtain an estimated SD (S2) of the ELC. Correlation (ρ) between the ELC measured at baseline and follow-up was assessed. Recalculation of the sample size was performed using analysis of covariance (ANCOVA) method which uses the design factor (1- ρ(2)). Adherence rate was calculated using a parent reported rate of missed doses of the study intervention.
Conclusion:
The new estimate of the SD of the ELC was found to be 17.40 (S2). The design factor was (1- ρ2) = 0.21. Using a significance level of 5%, power of 80%, S2 = 17.40 and effect estimate (Δ) ranging from 6-8 points, the new sample size based on ANCOVA method ranged from 32-56 subjects (16-28 per group). Adherence ranged between 14% and 100% with 44% of the children having an adherence rate ≥ 86%. Information generated from our internal pilot study was used to update the design of the full and definitive trial, including recalculation of sample size, determination of the adequacy of adherence, and application of strategies to improve adherence.
Trial Registration:
ClinicalTrials.gov Identifier: NCT01481766 (date of registration: November 22, 2011).
