Initial drug regimen for active tuberculosis cases in Montreal, 1995 to 1998

Abstract

Objectives: To evaluate the proportion of tuberculosis (TB) cases initially treated with the recommended four-drug regimen of isoniazid (INH), rifampin (RIF), pyrazinamide (PZA) and ethambutol (EMB) or streptomycin; and to identify factors associated with the choice of initial therapy.

Design: Descriptive analysis of surveillance data obtained by TB case notifications from physicians and microbiology laboratories.

Setting: The island of Montreal (with a population of 1,854,435 people).

Study population: All TB cases reported between January 1, 1995 and December 31, 1998.

Outcome measure: The proportion of TB cases initially treated with a four-drug regimen by sex, age, country of birth, site of disease and year of reporting.

Main results: Seven hundred forty-one cases were reported during the study period. Among the 687 analyzed cases, 406 (59.1%) received the recommended initial four-drug regimen (INH-RIF-PZA-EMB), 187 (27.2%) received an INH-RIF-PZA regimen, 61 (8.9%) received an INH-RIF-EMB regimen and 33 (4.8%) received an INH-RIF regimen only. In a logistical regression model, a four-drug regimen was significantly associated with respiratory disease (odds ratio [OR] 4.48; 95% CI 3.15 to 6.39), age younger than 65 years (OR 2.32; 95% CI 1.55 to 3.45), being foreign-born (OR 1.62; 95% CI 1.06 to 2.48) and later year of reporting (OR 1.27; 95% CI 1.09 to 1.47).

Conclusions: The proportion of TB cases initially treated with a four-drug regimen has increased steadily since 1995, reaching 65% in 1998. However, given the rate of INH resistance in Montreal, efforts to promote the use of the initial four-drug regimen must continue.

Keywords: Antitubercular agents; Communicable disease control; Disease notification; Microbial drug resistance; Multidrug-resistant tuberculosis; Population surveillance; Public health; Tuberculosis.