Two way sensitivity analyses of the sensitivity and specificity of HSV-2 type specific ELISA. Each line represents a different estimate of ELISA specificity. Two way sensitivity analyses of the sensitivity and specificity of HSV-2 type specific ELISA. Each line represents a different estimate of ELISA specificity. For any specificity, increasing sensitivity results in a decrease in the incremental cost effectiveness ratio of screening relative to no screening. Where ELISA specificity is equal to 80% or 90%, the cost effectiveness ratio represented is that of ELISA→WB relative to no screening. When ELISA specificity is equal to 100%, screening with ELISA→WB (broken line) costs more, but is no more effective than screening with ELISA alone (bottom solid line), and so is dominated by the latter strategy. Asterisk represents the base case. D N Fisman et al. Sex Transm Infect 2003;79:45-52 ©2003 by BMJ Publishing Group Ltd