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

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.

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

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

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

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.

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).

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.