Figure 3

Predictive relationship between pool size, number of tests and confidence intervals. Panel A: Expected point estimate and confidence interval for pools of sizes 2 through 30. Blue line and band represent point estimate and confidence interval for an imperfect test based on the values calculated in the LCM (True Prevalence: 8.0%, Sensitivity: 96.0%, Specificity: 99.1%). Confidence interval is not shown for pool sizes where confidence interval includes 100% prevalence (pool sizes >25). Green line and shaded area represent point estimate and confidence interval for a perfect test as would be assumed setting PCR as a gold standard (true prevalence 8.4%, sensitivity: 100%, specificity: 100%). Point estimate and confidence intervals for samples processed individually using imperfect test characteristics represented in black. Panel B: Expected number of tests required for one-step and two-step pooling strategies by pool size. Closed blue circle represents individual testing. Open blue circles represent expected number of tests from randomly-mixed one-step pools with an imperfect test. Closed green circles represent expected number of tests from two-step pools with an imperfect test. Reduction in number of tests relative to individual testing (individual tests/pooled tests) is represented for two-step pooling (green solid line) and one-step pooling (blue solid line).