Tuberculosis among Tibetan immigrants from India and Nepal in Minnesota, 1992-1995

Objective.-To study screening outcomes among a group of Tibetan immigrants at high risk for developing active tuberculosis (TB) after arrival in Minnesota. Design.-Retrospective cohort study. Participants.-A total of 191 Tibetan immigrants undergoing medical screening. Main Outcome Measures.-Occurrence and treatment outcomes of active TB. Setting.-A health maintenance organization and a public TB clinic in Minneapolis, Minn. Results.-Positive (induration, greater than or equal to 10 mm) tuberculin skin test results were documented in 98% of Tibetans, compared with 44% of Vietnamese, 10% of Hmong, and 51% of Russian refugees in Minnesota (P<.001 for each group). Sixteen active cases (8.4%) were confirmed by isolation of Mycobacterium tuberculosis; however, 5 (31%) were culture-negative on initial screening in Minnesota. Seven cases (44%) were diagnosed during initial screening efforts, and 9 cases (56%) were diagnosed a mean of 19 months (range, 10-27 months) after their initial medical evaluation. Of these 9 cases, 6 (38% of all Tibetan cases) had isolates resistant to 1 or more antituberculous drugs, and 3 (19% of all Tibetan cases) were multidrug resistant (MDR TB). All 3 MDR TB cases were culture-negative on initial screening; these cases constituted 75% of the MDR TB isolates in Minnesota in 1994. The presence of MDR TB was associated with a known history of active TB in Asia (P<.02), Any abnormality on chest radiograph noted either during the Immigration and Naturalization Service screening evaluation in India (relative risk [RR], 5.2; P=.006) or on arrival in Minnesota (RR, 6.8; P=.005) was associated with an increased risk of subsequent active TB. Conclusions.-Tuberculosis infection is nearly universal among Tibetans settling in Minnesota, A single screening evaluation failed to detect the majority of TB cases among Tibetans. Even in the face of negative M tuberculosis cultures, persons with a history of active TB require particularly close follow-up.