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Table 2 Statistical power for comparison of outcomes among study arms

From: Testing strategies for couple engagement in prevention of mother-to-child transmission of HIV and family health in Kenya: study protocol for a randomized controlled trial

1. CHTC uptake (assuming 23% uptake in the standard care arm (arm 3))

 Proportion (%) of CHTC uptake in arm 1 or arm 2

31

33

35

37

 Corresponding odds ratio (ref = arm 3)

1.50

1.65

1.80

1.97

 Power (%) to detect a significant difference among arms at 0.017 significance level with an auto-correlation (rho) = 0.50

63

84

95

99

 Power (%) to detect a significant difference among arms at 0.017 significance level with an auto-correlation (rho) = 0.10

87

97

100

100

2. HIV-free child survival at 18 months (assuming 91% survival in the standard care arm (arm 3))

 Proportion (%) of HIV-free survival in arm 1 or arm 2

93

95

97

99

 Corresponding odds ratio (ref = arm 3)

1.31

1.88

3.20

9.79

 Power (%) to detect a significant difference among arms at 0.025 significance level

7

26

62

93

3. Maternal viral load suppression at 18 months (assuming viral load suppression of 85% in the standard care arm (arm 3))

 Proportion (%) of viral load suppression in arm 1 or arm 2

90

92

94

96

 Corresponding odds ratio (ref = arm 3)

1.59

2.03

2.77

4.24

 Power (%) to detect a significant difference among arms at 0.025 significance level

24

49

77

94