ABSTRACT

Aims:

To determine the culture positivity rate in patients suspected of having smear-negative pulmonary tuberculosis (PTB) and to determine the contribution of tuberculin skin test to discrimination of culture positive cases from culture negative cases and active PTB from inactive cases.

Method:

According to hospital records (1999-2002), 77 patients suspected of having smear-negative PTB were studied. One hundred and thirteen sputum, 57 gastric aspiration fluid and 33 bronchial washing fluid specimens were examined and none of them was positive for acid-fast bacilli under the microscobic examination. The cases were groupped as high, intermediate and low risk for PTB according to their chest X-rays. Culture positivity rates for Mycobacterium tuberculosis (MTB) were compared among groups. Tuberculin skin test results were compared to determine whether there was a difference between culture positive and negative groups and active PTB and inactive cases.

Results:

Thirty seven of the patients had culture positivity for MTB at least in one specimen (48%). The mean value of tuberculin skin test results is higher in culture positive group than in culture negative group. In addition, this value is also higher in cases with active ATB than in inactive cases, but none of them were statistically significant.

Conclusion:

The incidence of active PTB is high in patients suspected of having smear-negative PTB. There are culture positive cases among the ones who are radiographically inactive. Tuberculin skin test seems that it has no contribution for discriminating culture positive cases from culture negative cases and active PTB from inactive cases.