Stability of Tuberculin Reaction.

P ERIODIC REPORTS HAVE EMPHASIZED the lack of stability of repeated tuberCulin skin tests in children. Kunofsky and Katz1 reported on two large groups in two schools for mental defectives. Reversion rates of 4 to 19 per cent were found. Marks et al.2 reported reversion rates between 12 and 26 per cent, depending on Criteria used, during a one-year period of observation of 1,100 tuberculin positive children. Adams et al.3 found the reversion rate for early converters to vary inversely with the initial degree of tuberculin positivity. Using National Tuberculosis Association definitions for tuberculin positivity, they found that children who were recent converters with a 1 + tuberculin skin test reaction had a reversion rate of 76 per cent within two years; 2+ initial tuberculin reactions had a reversion rate of 50 per cent; 3+ initial reactions had a rate of 38 per cent; and 4+ initial tuberculin reactions had a reversion rate of 17 per cent. The 160 children were mainly under 16 years of age, and 50 per cent were under six years of age. Kent and Blum4 report a one year reversion rate of 7.6 per cent among school children. In their series, the reversion rate dropped sharply for children older than 12 years. Dahistrom ei al.5 reported a reversion rate of 3.6 per cent per year for untreated and 15 per cent for children treated with isoniazid. Kunofsky and Katz stated: “Although most emphasis is placed in this study upon changes involving decreases or loss of sensitivity, the unstable tuberculin reaction may,