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 t uberculosis in certain high-risk groups, ie, infected contacts 50 year s and older, and to study the safety of isoniazid (INH) preventive the rapy in such persons. Design: From 1987 to 1992, two-part questionnair es were sent to each of the regional health offices within the 95 coun ties of Tennessee to document cases of purified protein derivative ski n test conversion or reaction among dose contacts of new patients with active tuberculosis. Infected contacts 50 years and older were includ ed in the study. Methods: Data collected from these questionnaires wer e 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 variou s groups as either twofold elevation or greater than threefold elevati on. Results: Of the 829 responses for persons fitting the criteria for INH chemoprophylaxis, 415 began treatment; 249 (60%) of those complet ed the full course (9 months) and 166 stopped prematurely. Of the 414 persons (50%) who did not start preventive therapy, 233 (56.5%) respon dents listed age as the reason, No patients started on a regimen of th erapy developed hepatitis, Of those completing therapy, 6.9% had a ris e in liver enzyme values but remained asymptomatic for hepatitis, Live r enzyme level elevation was significantly higher among patients who d iscontinued therapy, particularly white women, than those who complete d the full course. Asymptomatic liver enzyme level elevation (greater than or equal to 3 times normal value), private practitioners' prefere nces, and patients arbitrarily stopping therapy were the leading reaso ns 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, indicat ing underutilization of this prevention strategy, particularly in cont acts older than 50 years.