Tuberculin sensitivity in tuberculosis.

Seven of twenty-eight (25%) patients with untreated tuberculosis had skin induration of less than 6 mm to one tuberculin unit (TU), and 3 (11%) to 10 TU PPD. Among twenty-four patients with lung disease, there were no detectable differences in radiological extent of disease between reactors and non-reactors to low-dose tuberculin. However, non-reactors were significantly more malnourished (P less than 0.02), excreted more bacilli (P less than 0.02) and took longer for sputum sterilization during chemotherapy (P less than 0.01). Early skin reactions (6-8 h) occurred in fourteen of twenty-four (58%) patients, but in none of twenty-four matched healthy controls (P less than 0.0001); the proportions giving delayed (48-72 h) reactions were similar. Although the patients had larger delayed reactions as a group (P = 0.04), this would not have been of value in making the diagnosis. Repeat tuberculin testing of subjects had a booster effect, but did not induce hypersensitivity in initially healthy non-reactors. All nutritional abnoalities observed in the patients, except arm muscle circumference and serum albumin, reverted to normal during chemotherapy, concomitant with clinical improvement and an increase in dermal reactivity to tuberculin. Antigen overload may lead to both skin anergy and undernutrition. The accelerated tuberculin skin reaction could offer a practical and specific, although not particularly sensitive, method of aiding the diagnosis of active tuberculosis.