Analysis of a community hospital employee tuberculosis screening program 31 months after its inception

The employee tuberculosis screening program for this 450-bed, medical-surgical hospital was evaluated as of November 30, 1975. On that date, there were 1,488 employees, excluding physicians and medical and nursing students. Of the 626 employees tested at least twice with purified protein derivative, 28 converted their test from negative (zero induration) to positive (greater than or equal to 10 mm of induration), and 20 converted their tests from weakly reactive (3 to 9 mm of induration) to positive (greater than or equal to 10 mm of induration and showing a 6-mm or greater increase in induration over that resulting from the first test). The rate of conversion (tests with purified protein derivative going from negative to positive) was no different between the groups with high and with low degrees of exposure to tuberculous patients, suggesting the possibility of nonhospital-acquired infection in the latter group. A direct relationship existed between increasing age and increasing rate of conversion, suggesting that some of the convertors were not newly infected, but were persons with boosted reactivity. These data illustrate some of the practical problems of monitoring for tuberculous infections and subsequently offering preventive therapy to convertors.