[Differences between smear positive and smear negative pulmonary tuberculosis]

The decision related to treatment initiation in smear-negative pulmonary TB is controversial. To determine differences between the characteristics of smear-negative, culture-positive pulmonary TB (Group D-) cases, we compared them with those patients who presented positive smear microscopy and cultures (Group D+). In addition, we compared the characteristics found in Group D- cases, in whom the treatment was started before confirmation by culture (sub-group D-TI) with those who were treated only after a positive culture was obtained (subgroup D-TD). We compared 270 patients of Group D+ with 48 of Group D-. The subgroups of Group D- (D-TI and D-TD) were compared with Group D+. Clinical symptoms, history, X-rays, other lung diseases and related extrapulmonary diseases were analysed Significant differences between groups D+ and D- related to age, history, X-rays and other lung diseases were found. There were no significant differences between Group D+ and subgroup D-TI, except for the age. The same and even more accentuated differences between Group D+ and D- were found between Group D+ and subgroup D-TD.

Group D- was divided into to subgroups: D-TI, similar to D+, determined the decision to immediately start the treatment and D-TD, completely different; other possible diagnoses were considered and decision of treatment was delayed until a positive culture was obtained. This conduct proved to be the correct one in these cases where the diagnosis by culture was available.