Exploration of a Novel Diagnostic Approach for Latent Tuberculosis

Abstract

Tuberculosis is a prevalent disease in Pakistan and latent carriers are a big source of spread. The aim of our study was to explore some unorthodox approach for the diagnosis of latent tuberculosis (LTBI) in children. We have compared Mantoux test, T-SPOT.TB test and immunohistochemistry for the diagnosis of latent tuberculosis. 55 children seeking tonsillectomy were selected for the study. Mantoux test was performed by injecting PPD intradermally in the middle third of the forearm. T- SPOT.TB test was performed on blood samples from the same patients. Immunohistochemistry was done on the excised tonsils of the children by using anti- mycobacterium tuberculosis antibody. None of the patients had clinical symptoms of tuberculosis. The results of Mantoux, T-SPOT.TB and immunohistchemical tests were compared. More positive results were obtained by IHC as compared to Mantoux and T-SPOT.TB tests. Overall, one (1.8%) subject was graded positive by Mantoux test, three (5.4%) were detected by T-SPOT.TB test and 08 (14.5%) were confirmed by immunohistochemistry. Children aged 12-14 years were the most affected by latent tuberculosis and prevalence was generally higher in girls as compared to boys. Multiple comparisons of groups showed significantly higher positivity by IHC as compared to Mantoux test (p=0.027). Although the difference between IHC and T- SPOT.TB was also evident, it did not reach statistical significance probably due to limited number of cases. Our findings suggest that immunohistochemistry is more efficient and sensitive technique for establishing an early and specific diagnosis of Mycobacterium tuberculosis infection as compared to Mantoux and T-SPOT.TB tests. We recommend to immunohistochemically stain excised tonsils of children to detect unsuspected cases of latent tuberculosis.