Bacteriological analysis of induced sputum for the diagnosis of pulmonary tuberculosis in the clinical practice of a general tertiary hospital

Abstract

Objective: To determine the diagnostic sensitivity of bacteriological analyses in induced sputum (IS) for the diagnosis of pulmonary tuberculosis (TB) and to identify the clinical characteristics associated with the confirmed diagnosis, as well as to determine the diagnostic yield of bronchoscopy carried out when IS tests negative for AFB in smear microscopy. Methods: A retrospective, cross-sectional study of patients suspected of having active pulmonary TB and referred to our clinic for sputum induction. We consecutively reviewed the laboratory data of all patients submitted to sputum induction between June of 2003 and January of 2006, as well as their electronic medical records. In addition, the results of the bacteriological analysis of bronchoscopic specimens collected from the patients whose AFB tests were negative in IS were reviewed. Results: Of the 417 patients included in the study, 83 (19.9%) presented IS samples that tested positive for TB (smear microscopy or culture). In the logistic regression analysis, radiological findings of cavitation (OR = 3.8; 95% CI: 1.9-7.6) and of miliary infiltrate (OR = 3.7; 95% CI: 1.6-8.6) showed the strongest association with the diagnosis of pulmonary TB. In 134 patients, bronchoscopy was carried out after negative AFB results in IS and added 25 (64.1%) confirmed diagnoses of pulmonary TB. Conclusions: In our clinical practice, the frequency of confirmed diagnosis of pulmonary TB using IS (19.9%) was lower than that previously reported in controlled trials. Cavitation and miliary infiltrate increase the diagnostic probability of pulmonary TB using IS. The use of bronchoscopy when IS tests negative for AFB significantly increases sensitivity in the diagnosis of pulmonary TB.Keywords: Tuberculosis, pulmonary; Diagnosis; Sputum. ResumoObjetivo: Verificar a sensibilidade diagnóstica da análise bacteriológica do escarro induzido (EI) para o diagnós-tico de tuberculose (TB) pulmonar e identificar as variáveis clínicas associadas com o diagnóstico confirmado. Além disso, avaliar o rendimento diagnóstico da broncoscopia realizada se a pesquisa de BAAR for negativa no EI. Métodos: Estudo transversal e retrospectivo de pacientes com suspeita de TB pulmonar ativa, encaminhados ao serviço para a indução de escarro. Foram revisados consecutivamente os registros laboratoriais de todos os pacientes submetidos à indução de escarro entre junho de 2003 e janeiro de 2006, assim como o prontuário eletrônico de cada caso. Também foram revisados os resultados bacteriológicos das amostras broncoscópicas coletadas dos pacientes cujos resultados de BAAR em EI foram negativos. Resultados: Dos 417 pacientes estudados, 83 (19,9%) tiveram resultados positivos (BAAR e/ou cultura) no EI. Na análise de regressão logística, os achados radiológicos de cavitação pulmonar (OR = 3,8; IC95%: 1,9-7,6) e de infiltrado de padrão miliar (OR = 3,7; IC95%: 1,6-8,6) associaram-se mais significativamente com o diagnóstico de TB pulmonar. A broncoscopia foi realizada, após resultado de BAAR negativo no EI...

Efficacy of Induced Sputum for the Diagnosis of Pulmonary Tuberculosis in Adults Unable to Expectorate Sputum

“…This might reflect that the attending physicians preferred to reach the presumptive diagnose of PTB based on radiological findings and start empirical therapy rather than performing more invasive procedures. Garcia et al 21 also reported that only 32% of IS smear negative patients were submitted to bronchoscopy for the confirmation of the diagnosis in clinical practice.…”

“…Garcia et al 21 showed that performing bronchoscopy after IS when smear results are negative increased the diagnostic yield of PTB by 64.1%. Although, only five of 24 patients (20.8%) who failed early diagnosis with IS underwent bronchoscopy in this study, the addition of bronchoscopy enabled early diagnosis of PTB in 60% (3 of 5) and increased bacteriologically confirmed diagnosis rate in 20% (1 of 5) ( Table 2 ).…”