The prevalence of tuberculin skin test positivity and the effect of BCG vaccinations on tuberculin induration size in the eastern Mediterranean region of Turkey
To evaluate the prevalence of tuberculin skin test (TST) positivity in Kahramanmaraş and interpret the size of purified protein derivative (PPD) induration with respect to the number of Bacillus Calmette-Guerin (BCG) scars and other factors. Materials and methods: A total of 2979 school children between the ages of 7 and 17 years were evaluated. On the basis of socioeconomic levels, 11 schools were selected and categorized into 3 subgroups: schools in the suburbs of the city (Group 1), schools in the city center (Group 2), and private schools (Group 3). Children were injected with 5 TU/0.1 mL of PPD and the sizes of induration were measured after 72 h. The number of BCG scars and the sizes of induration were recorded for each pupil. Results: The TST was positive in 6.3% of the nonvaccinated students and in 7.5% of the vaccinated students (P > 0.05). The number of BCG vaccination scars was 0 in 174 children (5.8%), 1 in 1232 children (41.4%), 2 in 1516 children (50.9%), 3 in 54 children (1.8%), and 4 in 3 children (0.1%). The mean diameter of the size of the PPD induration for 0, 1, 2, 3, and 4 BCG vaccinations was 2.50 ± 4.05 mm, 5.60 ± 5.11 mm, 8.49 ± 5.09 mm, 8.46 ± 4.38 mm, and 7.66 ± 6.80 mm, respectively. The size of the induration was greatest in students vaccinated twice (P < 0.05). The TST positivity rate was highest in children 11-13 years of age (P < 0.05). Conclusion: The BCG vaccination rate was higher in Kahramanmaraş, whereas the TST positivity rate was lower. The factors that affected the size of the PPD induration were the number of vaccination scars and the age of the subject.
Key words: Bacillus Calmette-Guerin vaccination, tuberculin skin test, tuberculosis