Active tuberculosis in surgical patients with negative preoperative sputum smear results

To determine the proportion of negative preoperative sputum smear results among patients presenting active TB, as identified through the evaluation of surgical samples.

A retrospective study of patients undergoing surgery between 2003 and 2006 at a university hospital and receiving a histopathological diagnosis of active or latent TB. We reviewed patient histories, TB-related clinical aspects, acid-fast bacilli (AFB) test results, type of surgery performed and histopathological findings in surgical samples.

We included 43 patients, 27 of whom were male. The mean age was 44 + or - 19 years. Twenty-eight patients had a history of TB (treated appropriately), and 15 reported no history of the disease. The main reason for seeking treatment was recurrent infection, followed by alterations seen in imaging studies. Of the 43 patients, 35 underwent preoperative AFB testing: 32 tested negative, and 3 tested positive. Among those 35 patients, the histopathological diagnosis was active TB in 26 and latent TB in 9. The 8 patients not submitted to preoperative AFB testing were also diagnosed with latent TB. The proportion of active TB in patients with negative sputum smear results was 72% (23/32), whereas that of negative sputum smear results in patients with active TB was 88% (23/26). Only 11.5% (3/26) of the patients had tested positive for AFB.

Direct sputum smear microscopy has a very low yield. Many previously treated patients can present negative sputum smear results and yet have active TB. Active TB can be mistaken for secondary infections or for cancer.