Pulmonary tuberculosis (TB) with a positive smear signifies a larger bacterial population in TB lesions whereas several negative smears suggest a smaller bacterial load. The latter should have milder clinical symptoms and signs.
To confirm above hypothesis, we retrospectively reviewed the clinical records and chest radiographs of total 1,199 patients with positive sputum cultures in an University Hospital at Taiwan.
In the 1,199 sputum-culture-positive pulmonary TB patients, 442 (36.9%) of them were smear-negative (SN) and 757 (63.1%) were smear-positive (SP). The mean age was significantly higher in SN (54.1 ± 18.1) than in SP patients (51.4 ± 17.2). The SN patients had less clinical symptoms of cough (84.2 %vs. 92.0 %), fever (50.0 % vs. 57.7 %) and body weight loss (62.5 % vs. 70.7 %). There were significantly more SP patients than SN patients with anemia (68.5 % vs. 61.5 %). In drug sensitivity tests, there was no difference of drug resistance between two groups for INH, RIF, EMB and KM, but SN patients had significantly more drug resistance for SM (17.9 % vs. 13.2 %). There were significantly more SN patients whose TB lesion involved within one lobe 38.7 % vs. 25.4 %), on the contrary, there were significantly more SP patients whose TB lesions involved three or more lobes (51.2 % vs. 37.9 %). The SN patients were more frequently than the SP patients with underlying diseases (54.1% vs. 45.0%). The former was significantly composed of more cancer patients. The mortality rate was significantly higher in SN patients compared to SP patients (12.7 % vs. 9.0 %).
The SN patients were significantly older and with less clinical symptoms e.g., cough, fever, and body weigh loss. However the SN patients were significantly more common with underlying diseases such as cancer and which might account for the higher mortality rate.
Patients with SN pulmonary TB usually have less clinical symptoms/signs but higher mortality. The physician should pay more attention to take care of them.
T.C. Tsao, None.