Characteristics of tuberculosis patients who generate secondary cases.

OBJECTIVE

To determine the characteristics of smear positive tuberculosis (TB) patients who generate secondary TB cases.

METHODS

Those smear positive TB patients detected by the Barcelona Tuberculosis Program between 1990-1993, and for whom contact studies had been performed, were studied. We analyzed the predictive role of the variables: age, sex, intravenous drug use (IVDU), the presence of the acquired immune deficiency syndrome (AIDS), human immunodeficiency virus (HIV) infection, radiology pattern, district of residence, history of imprisonment, alcoholism, smoking, history of TB, treatment compliance and the number of secondary cases generated. Statistical analysis was based on the logistic regression model, calculating the odds ratios (OR) with 95% confidence intervals (CI).

RESULTS

Of the 1079 patients studied, 78 (7.2%) had generated only one secondary case, and 30 (2.8%) two or more. The variables associated with generating two or more secondary cases were: IVDU (P < 0.001; OR = 4.06; CI: 1.80-9.15), cavitary radiology pattern (P = 0.002; OR = 3.69; CI: 1.62-8.43), and age (P = 0.016; OR = 0.98; CI: 0.96-0.99). When we examined those who had generated one or more secondary cases, the following variables were significant: IVDU (P = 0.043; OR = 1.75; CI: 1.02-3.02), cavitary radiology pattern (P < 0.001; OR = 3.07; CI: 1.98-4.77) and age (P < 0.001; OR = 0.98; CI: 0.97-0.99).

CONCLUSION

The study of the contacts of smear positive TB patients allows us to detect an important number of secondary cases. Young adults, those with cavitary radiology pattern, and IVDU are more likely to generate secondary cases.