Determining a Bayesian predictive power stopping rule for futility in a non-inferiority trial with binary outcomes

Seamless phase 2/3 design for trials with multiple co-primary endpoints using Bayesian predictive power

Seamless phase 2/3 design has become increasingly popular in clinical trials with a single endpoint. Trials that define success based on the achievement of all co-primary endpoints (CPEs) encounter the challenge of inflated type 2 error rates, often leading to an overly large sample size. To tackle this challenge, we introduced a seamless phase 2/3 design strategy that employs Bayesian predictive power (BPP) for futility monitoring and sample size re-estimation at interim analysis. The correlations among multiple CPEs are incorporated using a Dirichlet-multinomial distribution. An alternative approach based on conditional power (CP) was also discussed for comparison. A seamless phase 2/3 vaccine trial employing four binary endpoints under the non-inferior hypothesis serves as an example. Our results spotlight that, in scenarios with relatively small phase 2 sample sizes (e.g., 50 or 100 subjects), the BPP approach either outperforms or matches the CP approach in terms of overall power. Particularly, with n1 = 50 and ρ = 0, BPP showcases an overall power advantage over CP by as much as 8.54%. Furthermore, when the phase 2 stage enrolled more subjects (e.g., 150 or 200), especially with a phase 2 sample size of 200 and ρ = 0, the BPP approach evidences a peak difference of 5.76% in early stop probability over the CP approach, emphasizing its better efficiency in terminating futile trials. It's noteworthy that both BPP and CP methodologies maintained type 1 error rates under 2.5%. In conclusion, the integration of the Dirichlet-Multinominal model with the BPP approach offers improvement in certain scenarios over the CP approach for seamless phase 2/3 trials with multiple CPEs.

A Mixed-Methods Cluster-Randomized Controlled Trial of a Hospital-Based Psychosocial Stimulation and Counseling Program for Caregivers and Children with Severe Acute Malnutrition

BACKGROUND

Children with severe acute malnutrition (SAM) who require nutritional rehabilitation unit (NRU) treatment often have poor developmental and nutritional outcomes following discharge. The Kusamala Program is a 4-d hospital-based counseling program for caregivers of children with SAM that integrates nutrition, water, sanitation, and hygiene and psychosocial stimulation, aimed at improving these outcomes.

OBJECTIVES

The aim was to evaluate the effects of the Kusamala Program on child development and nutritional status in children with SAM 6 mo after NRU discharge. The other aim was to qualitatively understand perceptions and experiences of caregivers who participated in the intervention.

METHODS

A cluster-randomized controlled trial was conducted with caregivers and their children 6-59 mo of age with SAM admitted to the Moyo NRU in Blantyre, Malawi. The primary outcome of the trial was child development according to Malawi Developmental Assessment Tool (MDAT) composite z-scores of gross motor, fine motor, language, and social domains. A qualitative component with focus group discussions and in-depth interviews was also completed with a subset of caregivers who participated in the trial.

RESULTS

Sixty-eight caregivers and children were enrolled to clusters by week and randomly assigned to the comparison arm and 104 to the intervention arm. There were no differences in child development, with mean MDAT composite z-scores in the comparison arm of -1.2 (95% CI: -2.1, -0.22) and in the intervention arm of -1.1 (95% CI: -1.9, -0.40) (P = 0.93). The qualitative evaluation with 20 caregivers indicated that the 3 modules of the Kusamala Program were appropriate and that they applied many of the lessons learned at home as much as possible.

CONCLUSIONS

The Kusamala Program did not result in improved developmental or nutritional outcomes, yet it was viewed positively by caregivers according to qualitative results. Future research should evaluate more intensive interventions for caregivers and children with SAM. This trial was registered at www.clinicaltrials.gov as NCT03072433.