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Table 3 Detectable effect sizes and assumptions used in sample size calculations for mortality and resistance primary outcomes for the AVENIR trial

From: Age-based targeting of biannual azithromycin distribution for child survival in Niger: an adaptive cluster-randomized trial protocol (AVENIR)

Trial Outcome Comparison Power Alpha Baselinea,b SD or ICCb Number of communities per arm Relative effect size Absolute effect size
Mortalityc Mortality in 1–59-month group Azithromycin 1–59 vs placebo 80% 0.05 27 deaths per 1000 person-years 0.019 1116 10% 2.7 per 1000 person-years
Mortality in 1–11-month group Azithromycin 1–11 vs placebo 80% 0.05
(if 1–59 group
P < 0.05)
45 deaths per 1000 person-years 0.068 1116 19% 8.8 deaths per 1000 person-years
Mortality in the 12–59-month group Azithromycin 1–11 vs azithromycin 1–59 80% 0.05
(if 1–11 group
P < 0.05)
24 deaths per 1000 person-years 0.018 1116 11% 2.7 deaths per 1000 person-years
Resistanced Prevalence of genetic determinants, NP swabs in 1–59-month group Azithromycin 1–11 vs placebo
Azithromycin 1–59 vs placebo
Azithromycin 1–11 vs 1–59
80% 0.05/2 30% 0.045 20 43% 13%
Load of genetic determinants, rectal swabs in 1–59-month groupe Azithromycin 1–11 vs placebo
Azithromycin 1–59 vs placebo
Azithromycin 1–11 vs 1–59
80% 0.05/2 2.13 0.02 20 70% 0.74
  1. ICC intra-class correlation coefficient, SD standard deviation
  2. a Refers to baseline mortality rate for mortality outcomes, and baseline prevalence or load of genetic determinants of macrolide
  3. resistance for resistance outcomes.
  4. b Estimated using data from the MORDOR Niger trial, SD reported for mortality rates and ICC for resistance
  5. c Calculations based on standard Z-test formula for power
  6. d Calculations based on Eqs. 7.11 and 7.12 for prevalence and load, respectively [19].
  7. e Load of genetic determinants of resistance presented on the log2 scale