Comparison of erythema and induration as results of tuberculin tests

Abstract

Setting: Schoolchildren, tuberculosis (TB) patients, and hospital employees in Tokyo, Japan.

Objective: To compare erythema and induration resulting from tuberculin tests among TB patients, normal children, and hospital employees with and without evidence of atopy.

Design: The distributions of diameters of erythema and induration were compared among three groups: 951 TB patients, 6139 first-grade and 6185 seventh-grade children, and 97 volunteer employees classified as atopic or non-atopic on the basis of skin tests and serum immunoglobulin E (IgE) concentrations.

Results: Erythema and induration were highly correlated. The distribution of erythema diameters was unimodal, and the distribution of induration diameters was bimodal. Erythema was considerably greater than induration among persons classified as being atopic.

Conclusion: Both erythema and induration appear to be adequate indices of tuberculin sensitivity. However, because most of the world uses induration as the index and virtually all studies of tuberculin sensitivity rely on induration, there are advantages in the use of induration. It would be desirable to initiate a large prospective study to see whether erythema or induration is the better predictor of subsequent tuberculous disease, and to confirm our finding that erythema is more likely to be confounded by atopy than induration.