The value of proper sputum collection instruction in detection of acid-fast bacillus

PURPOSE: This study was conducted to assess clinically whether intervention with instruction applying respiratory rehabilitation method for expectorating sputum was useful or not to obtain more suitable sputum for smear examination of acid-fast bacilli. SUBJECT: All specimens examined were sputa obtained from 163 patients without the instruction group and 161 patients with the instruction group, who visited our outpatients clinic during one year from September 1, 2000 to August 31, 2001 and the following one year, respectively. METHOD: Gross appearance of the sputum according to Miller & Jones' classification (M1, M2, P1-P3) and smear positive rate by fluorescence staining method after N-Acetyl-L-cysteine-NaOH treatment and centrifugation were compared between the two groups. RESULTS: M1 and P1 sputa were 21.5% and 21.5% in the no instruction group, while those were 8.1%, 36.6% in the instruction group. Difference in M2, P2 and P3 sputa were not significant between the groups. Smear positive rate was 10.4% in the no instruction group, while it was 21.1% in the instruction group. According to gross appearance of M2, P1 and P2, positive rate was 11.1%, 11.4% and 30.8% in the no instruction group, and 17.7%, 28.8%, and 26.3% in the instruction group. Chest roentogenographic findings judged by type (cavitary and non-cavitary) and extent of the pulmonary lesions of these smear positive cases (17 in the no instruction group and 34 with the instruction group), revealed that the no instruction group consisted of more predominantly severer disease with cavity and moderately or far advanced lesions as compared with the instruction group. CONSIDERATION: We could exclude that the difference in gross appearance and smear-positive rate of the sputum specimen between groups without and with the instruction might be due to differences in disease severity between the two groups with and without the instruction. CONCLUSION: The instruction for sputum expectoration seems to be useful to increase positive rate in the smear examination of acid-fast bacilli.