Comparing Tuberculin Anergy Skin Test Reactions and Lymphoblastic Transformation in Medical Students

Background: Tuberculin Skin Test (TST) reaction is an accepted screening test for diagnosing acute and latent Tuberculosis (TB) infection among at-risk populations. It is performed with a standard Protein Purified Derivative (PPD) solution. The skin reaction of PPD is unreliable to distinguish natural infection from the Bacillus Calmette Guerin (BCG) effect. The present survey aimed to determine the prevalence of Tuberculin Anergy (TA) reactions among medical students. Accordingly, we evaluated its sensitivity, specificity, and efficiency by applying the Recall Panel Antigen Test (RPAT) and the Lymphoblastic Transformation Test (LTT). Methods: The participants were sequentially enrolled in this study according to the designed protocol. The current study was conducted on healthy medical students before registering for the hospital training course. All research subjects were healthy, having a cicatrix of Bacillus Calmette Guerin (BCG) vaccination on the arm, and at a young age (20-24 years). Results: In total, 180 medical students met the inclusion criteria of the study. The study subjects’ Mean±SD age was 22±3.07 years (male=89, female=91). Moreover, 75 (42%) subjects presented a TA reaction in the first step of TST screening. Furthermore, 13 (64%) individuals presented a negative result of the RPAT. The sensitivity and specificity of the TST reactions, compared with the LTT were 100% and 94.4 %, respectively. Conclusion: Significant TA reactions were found among medical students with positive cicatrix post-vaccinated. The obtained data suggested that the BCG protection for individuals may be decreased as time expired. Consequently, the medical students will especially be at high risk for TB infection during the clinical training course. The collected data highlighted the patient-safety from the viewpoint of forensic medicine.