Tuberculosis among Tibetan immigrants from India and Nepal in Minnesota, 1992-1995
D. H. Truong, L. L. Hedemark, J. K. Mickman, L. B. Mosher, S. E. Dietrich and P. W. Lowry
Division of Epidemiology, University of Minnesota School of Public Health, Minneapolis 55454-1015, USA.
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, > or =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.
