COST-EFFECTIVENESS OF NONINVASIVE OXYGEN-SATURATION MEASUREMENT DURING EXERCISE FOR THE DIAGNOSIS OF PNEUMOCYSTIS-CARINII PNEUMONIA

We assessed (1) the sensitivity and specificity of exercise oxygen sat uration measurement (EOS) for the diagnosis of Pneumocystis carinii pn eumonia (PCP); and (2) the cost of introducing this indirect diagnosti c test compared with that of standard diagnostic strategies for PCP. I n a prospective study, 85 HIV-infected patients with suspected PCP und erwent EOS, followed by induced sputum (IS) and bronchoalveolar lavage (BAL) if IS was negative for P. carinii. The prevalence of PCP was 0. 22, the sensitivity of IS was 0.6, and its specificity was perfect. Th e cost ratios of IS to BAL and EOS to BAL were 0.1 and 0.2, respective ly. A desaturation of three points was the best cutoff point, giving p erfect sensitivity and a specificity of 0.77. The cost analysis showed that the introduction of EOS into diagnostic strategies for PCP is hi ghly justified when the local prevalence is low. Exercise oxygen satur ation measurement is simple and safe, and the results are available ra pidly; its sensitivity is perfect and its specificity good. Its econom ic utility depends on its cost and the local prevalence of PCP in the test population.