Tuberculin skin test reactivity of health care students in a country with a low prevalence of tuberculosis
OBJECTIVE: To analyse the distribution of tuberculin skin test (TST) reactions and epidemiological factors related to TST reactivity.
DESIGN: TST reactivity was analysed in 1190 students. A linear regression model was created for the relative contribution of background factors of TST reactivity. A subgroup of 287 non-vaccinated subjects was comparatively skin-tested with Mycobacterium avium sensitin and tuberculin.
RESULTS: Among non-bacille Calmette-Guérin (BCG) vaccinated students, 91% had no TST reaction (0 mm induration) and reactions of ≥10 mm were found in 2.9%, whereas 34% of BCG-vaccinated students had no TST reaction and 42% had reactions of ≥10 mm. The expected contribution to TST reactivity was 6.0 mm for a history of BCG vaccination, 3.0 mm for a country of birth with medium/high incidence of TB and 1.6 mm per 10 years of age. The sensitin reactions exceeded the TST reactions by ≥3 mm in 52% of the comparatively tested subjects with TST reactions of ≥1 mm.
CONCLUSION: BCG vaccination, cross-reactivity with non-tuberculous mycobacteria, geographic origin and age had a decisive influence on TST reactivity. Most non-vaccinated health care students were non-reactive, which highlights the need to organise preventive measures in settings where TB exposure is expected.
Document Type: Regular Paper
Affiliations: 1: Department of Respiratory Medicine and Allergology, Institute of Internal Medicine, The Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden 2: Department of Microbiology and Immunology, Institute of Biomedicine, The Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden 3: Department of Medicine, Division of Respiratory Medicine, Karolinska University Hospital, Stockholm, Sweden
Publication date: 2010-10-01
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