Design, methodology and results of an Internal Pilot Study for a RCT aimed at optimizing early child development in the primary-care setting (OptEC).
CPS ePoster Library. Abdullah K. 06/25/15; 99207; 145
Dr. Kawsari Abdullah
Dr. Kawsari Abdullah
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Abstract
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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 (56-99 per group). Given the uncertainty regarding the standard deviation (SD, S1 =15) used to calculate the sample, an internal pilot study was conducted.
Objectives: The objectives of this internal pilot were to obtain a reliable estimate of the standard deviation (S2) for the primary outcome of the OptEC trial; to recalculate the sample size of the OptEC trial using the estimates generated from the internal pilot; and to assess the adherence rate and causes of non-adherence in children enrolled in the pilot study.
Methods: The first 30 subjects (15 per group) enrolled into the OptEC trial constituted the internal pilot study. The primary outcome of the OptEC trial is a formal developmental assessment called the Early Learning Composite (ELC), assessed at baseline and 4 months following intervention. For estimation of the SD, 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. Recalculation of the sample size was performed using analysis of covariance (ANCOVA) method. Adherence rate was calculated using a self- reported rate of missed doses of the study intervention.
Results: The new estimate of the SD of the ELC was found to be 17.40 (S2). 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 rate ranged between 14% and 100% with 44% of the children having an adherence rate ≥86%.
Conclusion: This type of design allows data-driven recalculation of the sample size of randomized trials. Application of the ANCOVA method increases the statistical power while reducing the number of subjects required for a trial. Adherence was found to be adequate to meet the objectives of the OptEC 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 (56-99 per group). Given the uncertainty regarding the standard deviation (SD, S1 =15) used to calculate the sample, an internal pilot study was conducted.
Objectives: The objectives of this internal pilot were to obtain a reliable estimate of the standard deviation (S2) for the primary outcome of the OptEC trial; to recalculate the sample size of the OptEC trial using the estimates generated from the internal pilot; and to assess the adherence rate and causes of non-adherence in children enrolled in the pilot study.
Methods: The first 30 subjects (15 per group) enrolled into the OptEC trial constituted the internal pilot study. The primary outcome of the OptEC trial is a formal developmental assessment called the Early Learning Composite (ELC), assessed at baseline and 4 months following intervention. For estimation of the SD, 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. Recalculation of the sample size was performed using analysis of covariance (ANCOVA) method. Adherence rate was calculated using a self- reported rate of missed doses of the study intervention.
Results: The new estimate of the SD of the ELC was found to be 17.40 (S2). 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 rate ranged between 14% and 100% with 44% of the children having an adherence rate ≥86%.
Conclusion: This type of design allows data-driven recalculation of the sample size of randomized trials. Application of the ANCOVA method increases the statistical power while reducing the number of subjects required for a trial. Adherence was found to be adequate to meet the objectives of the OptEC trial.
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