[Evaluation of tuberculin reactivity in different age groups with and without BCG vaccination]

Tuberculin skin test (TST) which is used in the diagnosis of tuberculosis disease and evaluation of latent tuberculosis cases, is an easily applied, reproducible and low cost test. This study was carried out to determine the tuberculin reactivity in BCG vaccinated and unvaccinated population, to investigate the variables (BCG vaccination, the number of BCG scars, age, sex) affecting tuberculin reactivity. It was also aimed to determine the annual risk of tuberculosis infection (ARTI). The study which was a cross-sectional epidemiological one, was carried out during July 2006-January 2007 in Antalya district center and the number of objects to be applied with TST was determined by Power analysis method. A total of 408 participants; 147 children aged 5-7, 165 young adults aged 14-25 and 96 elderly people aged over 60, were included to the study. TST was applied by Mantoux method using 0.1 ml of purified protein derivative (PPD) RT 23/tween 80 antigen containing 5 tuberculin unit (TU). Evaluation of the test is done according to the domestic tuberculin skin test evaluation criteria. It was determined that 83.5% (341/408) of the cases were vaccinated with BCG and the diameter of TST was significantly higher in the vaccinated group when compared to the unvaccinated group (p= 0.005). Mean tuberculin reactivity (diameter of the TST induration) was 2.70 +/- 2.96 mm in 5-7 years age group, 6.44 +/- 4.11 mm in 4-25 years age group and 4.48 +/- 3.72 mm in > or = 60 years age group. Mean TST diameter was statistically significantly higher in 14-25 years age groups compared to 5-7 years (p= 0.003) and > or = 60 years (p= 0.002) age groups. Among the BCG unvaccinated group TST positivity was none in 5-7 years, 2% in 14-25 years and 7% in > or = 60 years age group. These rates were none in 5-7 and > or = 60 years age groups and 1% in 14-25 years age group in the BCG vaccinated population. It was also observed that TST diameters increased with increasing number of BCG scars and there was no difference in sex dependent TST reactivity. Average ARTI was determined to be 6%. It was concluded that to determine the risk of tuberculosis, annual variation in the ratio of ARTI has to be determined by nationwide evaluation of tuberculin skin test.