Extra-pulmonary tuberculosis: differential aspects and role of 16S-rRNA in urine

Early diagnosis of extra-pulmonary tuberculosis (EPTB) is important for successful treatment.

All cases of EPTB diagnosed at Ramon y Cajal Hospital, Madrid, Spain, from 1997 to 2008 were analysed and compared with pulmonary tuberculosis (PTB) patients to identify differential parameters that could serve to predict the presence of EPTB at initial presentation. Different microbiological techniques were analysed, including amplification of 16S-rRNA in urine.

During the study period, 814 cases of TB were diagnosed at our centre; 330 (40.5%) were EPTB. Concomitant PTB was detected in 45% of EPTB cases. The main clinical forms of EPTB were lymphadenitis (86, 26%), miliary TB (60, 18%), and multifocal TB (43, 13%). Variables independently associated with EPTB were human immunodeficiency virus (HIV) infection (OR 3.6, 95%CI 2.4-5.4), older age (>60 years) (OR 3.7, 95%CI 2.5-5.6) and mortality (OR 2.9, 95%CI 1.3-6.3). 16S-rRNA in urine was performed in 82 EPTB patients (25%), among whom a positive result was obtained in 70%; in the PTB group, a positive result was found in 5 of 28 patients (18%) (P <0.001).

HIV infection and older age appear to be the main risk factors associated with EPTB. In this study, mortality was significantly higher in patients with EPTB. A positive 16S-rRNA test result in urine is a useful marker of EPTB.