RESUMO
We assessed (1) the sensitivity and specificity of exercise oxygen saturation measurement (EOS) for the diagnosis of Pneumocystis carinii pneumonia (PCP); and (2) the cost of introducing this indirect diagnostic test compared with that of standard diagnostic strategies for PCP. In a prospective study, 85 HIV-infected patients with suspected PCP underwent 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. The cost ratios of IS to BAL and EOS to BAL were 0.1 and 0.2, respectively. A desaturation of three points was the best cutoff point, giving perfect sensitivity and a specificity of 0.77. The cost analysis showed that the introduction of EOS into diagnostic strategies for PCP is highly justified when the local prevalence is low. Exercise oxygen saturation measurement is simple and safe, and the results are available rapidly; its sensitivity is perfect and its specificity good. Its economic utility depends on its cost and the local prevalence of PCP in the test population.
Assuntos
Infecções Oportunistas Relacionadas com a AIDS/economia , Monitorização Transcutânea dos Gases Sanguíneos/economia , Teste de Esforço/economia , Pneumonia por Pneumocystis/economia , Infecções Oportunistas Relacionadas com a AIDS/diagnóstico , Infecções Oportunistas Relacionadas com a AIDS/epidemiologia , Adulto , Monitorização Transcutânea dos Gases Sanguíneos/estatística & dados numéricos , Líquido da Lavagem Broncoalveolar/economia , Análise Custo-Benefício , Teste de Esforço/estatística & dados numéricos , Feminino , Infecções por HIV/diagnóstico , Infecções por HIV/economia , Infecções por HIV/epidemiologia , HIV-1 , Humanos , Masculino , Pessoa de Meia-Idade , Paris/epidemiologia , Pneumocystis/isolamento & purificação , Pneumonia por Pneumocystis/diagnóstico , Pneumonia por Pneumocystis/epidemiologia , Prevalência , Estudos Prospectivos , Curva ROC , Sensibilidade e Especificidade , Escarro/microbiologiaRESUMO
Sputum induction (SI) is a sensitive and specific method for diagnosing Pneumocystis carinii pneumonia (PCP) in patients with AIDS. Although less expensive than bronchoscopy with bronchoalveolar lavage (BAL), SI followed by BAL does not necessarily reduce costs compared with BAL alone. Cost analysis demonstrates that the cost of diagnosing PCP is dependent on the prevalence of PCP (PCPprevalence) in the studied population, the sensitivity of SI (SIsensitivity) for diagnosing PCP, and the relative costs of SI and BAL (SIcost and BALcost) for diagnosing PCP. In any given clinical setting, SI reduces the cost of diagnosing PCP if (PCPprevalence)(SIsensitivity) greater than SIcost/BALcost. A graphic approach relating these parameters is also presented. Evaluation of reported PCPprevalence and SIsensitivity from recent literature illustrates that SI is not always the least costly method for diagnosing PCP. Cost reduction is not the only measure of a diagnostic procedure's value, and other aspects, such as discomfort, availability, risks, and patient prognosis, must be considered. The cost analysis approach used in this study identifies those variables that can be manipulated to reduce the cost of diagnosing PCP.
