Comparison of extra-pulmonary and pulmonary tuberculosis cases: factors influencing the site of reactivation.

SETTING: Mycobacterium tuberculosis bacilli spread by the hematogenous route during primary infection and reactivate later.

OBJECTIVE: To compare factors influencing the reactivation site.

DESIGN: A total of 236 pulmonary tuberculosis (PTB) and 139 extra-pulmonary TB (EPTB) cases were compared in terms of age, co-morbid disease, immunosuppressive drug use, history of contact with a PTB case in a close relative, history of tuberculosis, smoking habit and alcohol intake.

RESULTS: The sex ratio of EPTB and PTB cases was significantly different (P < 0.001): respectively 74% of EPTB cases and 34% of PTB cases were females; 53.3% of PTB cases and 23% of EPTB cases were smokers (P < 0.001); and the disease appeared within the first 5 years after contact in 23.7% of EPTB cases compared to 72.6% in PTB cases (P < 0.001). In logistic regression analysis, gender (OR = 3.69), smoking habit (OR = 0.54) and interval between contact and disease (OR = 1.07) were found to influence the reactivation site.

CONCLUSION: The probability of PTB development was higher in males, in smokers and within the first 5 years of contact. In contrast, the probability of EPTB development was higher in females and after 5 years of contact.