The association of airway hyperresponsiveness and tuberculin responses.

BACKGROUND

The balance between the two subsets of T cell is pivotal for allergic sensitization.

OBJECTIVE

We conducted a cross-sectional study of 486 children vaccinated with bacillus Calmette-Guérin (BCG), aged 10-13 years, to evaluate whether tuberculin responses may contribute to airway hyperresponsiveness (AHR).

METHODS

Tuberculin skin test, allergic skin test, and methacholine challenge test were done. The methacholine concentration causing a 20% fall (PC20) in forced expiratory volume in 1 second (FEV1) was used as a threshold of AHR. Atopy was defined as a reaction showing a mean wheal size of > or = 3 mm to one or more allergens on skin prick test (SPT). Two tuberculin units of polysorbate-stabilized purified protein derivatives (PPD) were injected intradermally into the volar surface of the forearm. Reactions were read at 48-72 h as the transverse diameter in millimeters of induration.

RESULTS

Of the children in the study, 12.3% (60/486) had PPD induration; 7.8% (38/486) of children had PPD induration of greater than 10 mm. The PPD induration size was 10.5 +/- 1.03 mm (confidence interval (CI) 7.19-12.33) in atopic children and 11.2 +/- 0.76 mm (CI 7.89-13.1) in nonatopic children. The differences of PPD induration diameter between the two groups were not significant. There was no difference of log PC20 between PPD induration > or = 10 mm and < 10 mm (0.13 +/- 0.18 vs. 0.42 +/- 0.05). The difference of log PC20 between positive and negative tuberculin response was not significant. Children with atopy had lower log PC20 than those without atopy (0.16 +/- 0.07 vs. 0.51 +/- 0.05, P = 0.001). After adjusting for sex, age, height, weight, tuberculin response, atopy was associated with AHR in multivariate analyses (odds ratio = 1.895, CI 1.285-2.505, P = 0.002).

CONCLUSION

These data suggested that a tuberculin response due to mycobacterial infection status have no effect on AHR in schoolchildren.