USE OF THE POLYMERASE CHAIN-REACTION TECHNIQUE ON INDUCED-SPUTUM SAMPLES FOR THE DIAGNOSIS OF PNEUMOCYSTIS-CARINII PNEUMONIA IN HIV-INFECTED PATIENTS - A CLINICAL AND COST-ANALYSIS STUDY

The purpose of this study was to assess the sensitivity and specificit y of tile polymerase chain reaction (PCR) on induced sputum (IS) for t he diagnosis of Pneumocystis carinii pneumonia (PCP) in HIV-infected p atients, as well as its diagnostic value and cost as a routine clinica l tool, Forty-nine patients with suspected PCP who had IS were studied and if negative, followed by bronchoalveolar lavage (BAL). Pneumocyst is carinii was detected in these samples using standard staining techn iques, Polymerase chain reaction was used with IS samples in a blinded fashion. The patients with negative BAL samples were closely monitore d for 1 month. In the absence of any clinical or radiologic features o f PCP during this period, they were considered as being free of PCP. T he cost analysis considered only the direct costs of the various tests in three diagnostic strategies: routine BAL (BAL); IS with standard s taining, if negative, followed by BAL (IS); and IS with standard stain ing followed, if negative, by PCR on IS samples (PCR-IS). Using standa rd staining, P carinii was found in 13 cases (6 IS and 7 BAL), None of the 36 patients with negative BAL developed further signs of PCP. Thu s, the prevalence of PCP was 26.5% and the sensitivity and specificity of BAL were 100%. Standard staining of IS had a specificity of 100% a nd a sensitivity of 46.5%. The sensitivity and specificity of PCR-IS w ere each 100%. The costs of strategies BAL, IS, and PCR-IS were $14,01 0, $18,300, and $18,040, respectively. The rests of the BAL strategy d epended only on the cost of the relevant tests, whereas the costs of s trategies IS and PCR-IS depended on the costs of the tests, the sensit ivity of IS with standard staining, and the prevalence of PCP in the t est population, The routine clinical use of PCR-IS is currently limite d by the time required to obtain the results.