[Primary prevention and treatment of latent tuberculosis infection with isoniazid: efficacy of a control program,...

To analyze the efficacy of a specific program for the study and follow up of tuberculosis contacts. To study factors related to low adherence to treatment and to the development of liver toxicity caused by isoniazid.

Between December 1996 and December 2002, we found 458 contacts of 79 cases of pulmonary tuberculosis in patients uninfected by human immunodeficiency virus. The contacts were screened for tuberculosis infection and chemoprophylaxis was prescribed according to the recommendations of the Spanish Society of Pulmonology and Thoracic Surgery (SEPAR).

We identified 3 cases of tuberculosis among the contacts (prevalence 0.8%). Chemoprophylaxis with isoniazid was prescribed for 215 contacts. One hundred sixty-nine (79%) completed the prophylaxis protocol. The rate of adherence to treatment was lower in immigrants than in nonimmigrants (odds ratio, 3.42; 95% confidence interval, 1.03-11.04; P=.02). Forty-three patients (22%) developed liver toxicity during treatment, which had to be suspended in 3 cases. Duration of chemoprophylaxis was the only independent variable associated with liver toxicity (odds ratio, 3.80; 95% confidence interval, 1.10-13.13; P=.03).

Our study demonstrates the effectiveness of a specific program of study and follow up of tuberculosis contacts. Immigrants require tailored strategies to improve their adherence to the program. The duration of chemo-prophylaxis plays an important role in the development of liver toxicity.