The Use of Sputum Cultures in the Evaluation of Immigrants Classified as Tuberculosis Suspects

Abstract

Because of possible deficiencies in the evaluation, based on symptoms and chest roentgenogram review, of new immigrants classified during the visa application process as tuberculosis suspects, a prospective (cohort) and a retrospective (case control) study were done to test the usefulness of routinely obtaining sputum specimens for culture in that settling. In the prospective study, 249 consecutive classified immigrants who were considered on the basis of clinical and roentgenographic findings to have nonprogressive tuberculosis submitted at least two sputums for culture: 13 (5.2%) had at least one culture positive for Mycobacterium tuberculosis. Immigrants younger than 50 yr of age and refugees from kampuchea and Laos had a fivefold to tenfold elevated risk of having a positive sputum culture. The cost per case detected of obtaining and processing sputum cultures was estimated to be $1,996 to $2,994. In the case-control study, 37 classified immigrants evaluated from 1981 through 1986 who had sputum cultures positive for M. tuberculosis even though they fulfilled clinical and roentgenographic criteria for nonprogressive tuberculosis served as cases; 48 immigrants similarly classified and evaluated but with negative sputum cultures served as control subjects. Several demographic, clinical, and roentgenographic factors were associated with an increased risk of being culture-positive; age younger than 50 yr, a positive tuberculin test, report of a cough, and a cavitary lesion on chest roentgenogram. The history of prior receipt of antituberculosis drugs was associated with having a negative with having a negative culture, including a marked dose-response effect.