Evaluation of Tuberculosis Skin Test in Al-Hilla Province

Abstract
Background: The accurate diagnosis of latent tuberculosis infection (LTBI) is an important component of any tuberculosis control programme and depends largely on tuberculin skin testing. The appropriate interpretation of skin test results requires knowledge of the possible confounding factors such as previous BCG vaccination. This study aimed to assess tuberculin skin testing in patient with latent tuberculosis infection.
Methods: The study was performed at Tuberculosis Centre in Babylon Province in the period from February 2016 to February 2017, it included 1109 patients.
History and physical examination were performed, the history included information about age, gender, address, history of contact with tuberculosis patients , and history of BCG vaccination. Tuberculin skin test was performed by mantox test,0.1 unit of purified tuberculin protein injected intra-dermally and read after 48 hours, the result was measured in millimeter (mm) .
Results: The age ranged from 1-85 years and the mean age was 24.30±20.241, percentage of females was more than males (52% versus 48%), the number of positive cases of BCG were 966 (87%) while the negative cases was 143 (13%),
the number of positive cases of tuberculin skin test was 86 (7.8%) while the negative cases were 1023 (92.2%). The diameter of skin test was higher in vaccinated subjects than non-vaccinated and the result was significant (p value=0.004).The number of positive skin test was higher in vaccinated than non-vaccinated patients and the difference was significant.
Conclusions: In subjects without active tuberculosis, immunization with BCG largely increases the likelihood of a positive tuberculin skin test. The interpretation of the skin test therefore needs to be made in the individual clinical context and with evaluation of other risk factors for infection. The size of the induration should also be considered when making recommendations for treatment of latent infection.