Tuberculin skin test reactions by time of reading among Dutch travellers.

SETTING: Five travel and TB control clinics in The Netherlands. OBJECTIVE: To assess the variation of skin test reactions between different days of reading. DESIGN: Cohort study of non-BCG-vaccinated travellers. Mantoux skin test data were analysed for associations between time interval between administration and reading and reaction size. RESULTS: There were no significant differences in reaction size to 1 TU PPD between readings at day 3 or 4, either for pre-travel (n = 1004) or post-travel (n = 577) tests, before (P = 0.990 and 0.210, respectively) or after exclusion of 0 mm reactions (P = 0.330 and 0.474). Time intervals were not different for reaction sizes of 0, 1-9 or > or = 10 mm (P = 0.826 and 0.306). There were also no significant associations for simultaneous tests with a sensitin of Mycobacterium scrofulaceum. CONCLUSIONS: Tuberculin skin tests can be read on day 3 or 4, without compromising their validity.