Summary of assumed intervention effects, clustering and power for primary and secondary outcomes
| Outcome | Intervention vs Control | CV* | ICC* | Assumed n per cluster† | Power‡ |
|---|---|---|---|---|---|
| Primary | |||||
| Proportion of fevers with test§ | 70% vs 31% | 0.40 | 0.073 | 40 | 98% |
| Secondary | |||||
| Proportion of ACT taken by those who test positive§ | 72.5% vs 36.5% | 0.17** | 0.017** | 10 | >99% |
| Proportion of ACT taken by those with no test§ | 16.9% vs 56.6% | 0.22 | 0.064 | 10 | >99% |
| Proportion who take ACT after a positive test§ | 90% vs 70% | 0.04** | 0.003** | 5 | NA†† |
| Proportion who take ACT after a negative test§ | 10% vs 10% | 0.25 | 0.007 | 7 | NA†† |
Values in each arm are calculated using the assumed probabilities from pilot data (shown on the branches of figure 3) where 37.4% of intervention and 25.6% of control arm participants are estimated to take ACTs.
*Clustering estimated using methods suggested by Hayes and Moulton (2009).23 Details for CV presented in the text with ICC estimated using ICC=CV2×π/(1-π), where π is the assumed control-arm proportion for the outcome.
†Set at the minimum of n per intervention arm cluster and n per control arm cluster, derived using assumed probabilities in figure 3 and based on 40 fevers per cluster.
‡Power at each of 3 follow-up time points for a cluster-randomised trial of 16 control CUs vs 16 intervention CUs at an overall 5% type-1 error rate for each outcome with Bonferroni correction for 3 time points.
§Assumptions based on pilot data as listed on the branches of figure 3.
**Values differ from the IRB protocol because a plausible range of values for the control arm used updated pilot data.
††Not applicable (NA) since assumed to be equal in both arms.
ACT, artemisinin combination therapy; CU, community units; CV, coefficient of variation; ICC, intraclass correlation coefficient; IRB, Institutional Review Board.