Assessing the interruption of the transmission of human helminths with mass drug administration alone: optimizing the design of cluster randomized trials

Table 7 Confidence limits (95%) for PPV and NPV values for simulations presented in Fig. 9. Prevalence threshold 30.0% two years after cessation of MDA. Data from 300 village simulations with 250 people per village

Raw data from 300 simulations	Bounce back	Transmission interruption	Totals
Test positive	6	232	238
Test negative	47	15	62
Totals	53	247	300
		95% Confidence limits
	Estimated value	Lower limit	Upper limit
Prevalence of interruption	0.823	0.774	0.864
Sensitivity	0.939	0.900	0.964
Specificity	0.887	0.763	0.953
Probability of simulation being either transmission interruption or bounce back
Interruption	0.792	0.742	0.837
Bounce back	0.207	0.163	0.258
For predicted elimination - probability of being true or false
True positive (PPV)	0.974	0.943	0.990
False positive	0.025	0.010	0.057
For predicted bounce back - probability of true or false
True negative (NPV)	0.758	0.630	0.854
False negative	0.242	0.146	0.5370
Likelihood ratios
Positive (C)	8.300	3.903	17.640
Negative (C)	0.068	0.042	0.112
Positive (W)	38.667	17.544	85.220
Negative (W)	0.319	0.203	0.501

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