Is it valuable to examine more than one sputum smear per patient for the diagnosis of pulmonary tuberculosis?

The simplest, cheapest, and fastest diagnostic method for tuberculosis (TB) is the detection of acid-fast bacilli (AFB) by microscopy. The algorithm advised for the diagnosis of TB recommends examination of three consecutive sputum specimens from TB suspects for the presence of AFB. In the present study, we evaluated the contribution of each specimen to the final detection of TB suspect patients with culture-proven disease. The collection and analysis of retrospective data on patients with culture-proven pulmonary TB, from June 2002 to August 2006 at Dokuz Eylul University Hospital, Turkey, have enabled us to assess the value of examining two sputum specimens in diagnosing this disease. AFB were detected from one or more sputum specimens with direct microscopy in 42% of the cases. An analysis of results of smear examination showed that 97% of AFB were detected from the first specimen and only 3% were obtained from the second smear. The third specimen did not have any additional diagnostic value for the detection of AFB by microscopy. As a conclusion the present study shows that examining two sputum smears is sufficient for the early detection of AFB in our laboratory.