Tuberculosis Among Tibetan Immigrants From India and Nepal in Minnesota, 1992-1995

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Abstract
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, ≥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.