Underutilization of isoniazid chemoprophylaxis in tuberculosis contacts 50 years of age and older. A prospective analysis.

STUDY OBJECTIVES

To examine the utilization of chemoprophylaxis for tuberculosis in certain high-risk groups, ie, infected contacts 50 years and older, and to study the safety of isoniazid (INH) preventive therapy in such persons.

DESIGN

From 1987 to 1992, two-part questionnaires were sent to each of the regional health offices within the 95 counties of Tennessee to document cases of purified protein derivative skin test conversion or reaction among close contacts of new patients with active tuberculosis. Infected contacts 50 years and older were included in the study.

METHODS

Data collected from these questionnaires were grouped according to age, sex, race, liver functions test (LFT), and whether chemotherapy was completed. Reasons for early discontinuation were also recorded. High values of LFTs were classified in the various groups as either twofold elevation or greater than threefold elevation.

RESULTS

Of the 829 responses for persons fitting the criteria for INH chemoprophylaxis, 415 began treatment; 249 (60%) of those completed the full course (9 months) and 166 stopped prematurely. Of the 414 persons (50%) who did not start preventive therapy, 233 (56.5%) respondents listed age as the reason. No patients started on a regimen of therapy developed hepatitis. Of those completing therapy, 6.9% had a rise in liver enzyme values but remained asymptomatic for hepatitis. Liver enzyme level elevation was significantly higher among patients who discontinued therapy, particularly white women, than those who completed the full course. Asymptomatic liver enzyme level elevation (> or = 3 times normal value), private practitioners' preferences, and patients arbitrarily stopping therapy were the leading reasons for incomplete INH preventive therapy.

CONCLUSION

We conclude that 30% of tuberculosis-infected contacts deserving chemoprophylaxis were actually provided the full benefit of INH preventive therapy, indicating underutilization of this prevention strategy, particularly in contacts older than 50 years.