Diagnosis of active tuberculosis by immunological methods. 2. Qualitative differences in the dermal response to tuberculin in patients with active pulmonary disease and healthy tuberculin-positive individuals.

The tuberculin reactivity of 107 patients with active pulmonary tuberculosis and 143 healthy age-matched control subjects were compared. At 48 hours 96% of patients and 76% of control subjects were positive reactors. The diameters of the reactions were of similar size. At 24 hours 93% of patients and 65% of controls were positive: the reactions tended to be larger in the patient group but the difference was of no diagnostic value. The greatest discrimination was apparent at 6-8 hours when 72% of patients and only 3.5% of control subjects reacted. Although probably an Arthus reaction, this early response did not correlate significantly with antibody levels measured by enzyme-linked immunosorbent assay. Accordingly the two tests, to some extent, complemented each other diagnostically.