Introduction & Objective: The World Health Organization estimates that 1.3 million Tubercu-losis cases occur in children each year. Due to the lack of sputum examination in children, the diagnosis of pediatric tuberculosis is based on three criteria close contact history, chest x ray finding and positive tuberculin skin test..On the other hand, BCG vaccine that in our na-tional immunization schedule, routinely administered is able to make a positive skin test. The aim of this study is to evaluate the tuberculin skin test reactions in children who have re-ceived BCG vaccine.

Materials & Methods: This analytic cross sectional study was performed on 564 cases of 1-6 year old children previously vaccinated with BCG at birth and chosen by cluster sampling. Data of each child obtained for age, sex and retained BCG scar. In the second step informed parental consent was obtained then TST was administered by injecting 0.1 ml of 5 units puri-fied protein derivated (PPD) into the volar surface of the forearm.The TST induration was measured 48-72 hours after injection of PPD .TST administration and measurement of indu-ration were done by trained healthcare workers. Data were analyzed with One-Way ANOVA and t-test by SPSS version14.

Results: In our study, out of 564 children, 288 were male and 278 were female. 319(56.4%) cases didn’t show any reaction . Out of all, 228 cases (40.6%) had TST reaction 1-10mm 9 cases (1.6%) had TST 10-15 mm and only 8 cases (1.4%) had TST induration>15 mm . Mean indurations diameter was 2.9±1.8 mm and according to the definition of positive TST only 12 cases (2.1%) had positive TST. There was no statistically sexual preference in TST reaction but with increasing of age induration diameter of TST decreased meaning that there is an inverse relationship between age and TST reaction.

Conclusion: According to our results, BCG vaccination at birth did not have any major effect in tuberculin skin test and each child with positive TST after 2 year age should be evaluated carefully.