Inverse association between positive tuberculin tests and positive allergy skin tests in children

Abstract

Background The association between Mycobacterium tuberculosis infection and atopy remains controversial. Reaction to tuberculosis infection is mediated by Th-1 immune responses whereas allergic reactions are mediated by Th- 2 immune response. In patients with atopic syndrome who also suffer from tuberculosis infection, the Th-2 response will be suppressed and allergy manifestations will decrease. Therefore, it is important to determine the appropriate allergy test and to predict outcome after completing tuberculosis treatment. Objective To evaluate the influence of a positive tuberculin test on skin test results in diagnosing atopic disease. Methods A cross sectional study was conducted in the pediatric allergy outpatient clinic, Soetomo Hospital, Surabaya, Indonesia between 2004 and 2007. Eighty-five patients were enrolled in this study. The tuberculin test was performed on all patients with allergy. The allergy test was carried out by performing a skin scratch test. Results There was a weak inverse correlation between positive tuberculin tests and positive allergy skin tests in children (house dust mite, food and pet allergies). The correlation between a positive tuberculin test and house dust mite allergy test was r: -0.364 (P=O.OOl; a=O.Ol). The correlation between the tuberculin test and food allergies was r: -0.420 (P=O.OOl; a=O.Ol). The correlation between the tuberculin test and pet allergies was r: -0.344 (P= 0.001; a=O.Ol). Conclusions A positive tuberculin test is weakly correlated with positive allergy skin test results, suggesting that it is appropriate to do allergy skin testing even in children with a positive tuberculin test.

Keywords

• allergy
• skin test
• tuberculin test
• inversed association