Comparison of diagnostic yield of AFB with sputum induction to spontaneous sputum examination in suspected pulmonary tuberculosis.

Abstract

To compare the diagnostic yield of AFB positivity with sputum induction to spontaneous sputum examination in suspected cases of pulmonary tuberculosis. Comparative study. Military Hospital, Rawalpindi, from January to December 2006. Sputum specimens were collected by both techniques from 164 patients with clinical and radiological suspicion of pulmonary tuberculosis admitted in medical wards. All specimens were examined for AFB smear and culture positivity. Sputum induction was done for 15-20 minutes with 3% sterile hypertonic saline solution by nebulization in all cases. Proportions were compared using Chi-square test. Among 164 patients, 32 patients (19.5%) were not expectorating spontaneously. Sputum induction was successful in 22 (68.75%) cases and AFB smear was positive in 03 (9.37%) and AFB culture was positive in 7 (21.8%) of these cases. One hundred and thirty two (80.5%) patients were already expectorating and both Day-1 (spontaneous) and Day-2 (induced) sputum samples were available. Day-1 (spontaneous) sputum specimens revealed AFB smear positive results in 20 (15.15%) patients, and AFB culture positive results in 24 (18.18%) patients. Smear positivity on Day-2 (induced) sputum samples was 21.21% (28) with 27.27% (36) culture positivity. In expectorating patients, AFB smear and culture positivity results remain comparable with spontaneous and induced sputum sampling. Sputum induction improves the diagnostic yield for AFB in patients unable to expectorate adequate sputum sample.