Targeting tuberculosis testing: the yield of source case investigations for young children with reactive tuberculin skin tests

Abstract

Objective: This study was designed to determine the yield of investigations whose aim is to identify a source case for tuberculosis infection among tuberculin reactors 3 years of age or younger.

Methods: The authors describe the results of associate investigations conducted for child tuberculin reactors reported from January 1, 1996, through June 30, 1998. Associates were defined as individuals who live with or spend significant time with a child reactor. An associate investigation was defined as evaluation of at least one associate. A source case was an associate older than 10 years of age who had culture-positive, pulmonary tuberculosis during a period when the child could have been exposed.

Results: Two hundred seven children had an associate investigation performed with a median of four associates investigated per child (range 1-21). Birthplace was known for 187 (90%); 128 were U.S.-born. Of 1,222 associates identified, 980 (80%) were evaluated. Among 452 (46%) associates for whom birthplace was known, 250 (55%) were non-U.S.-born. Of 980 associates, 668 were household contacts; 198 (30%) were infected, three had prior tuberculosis disease, and three had active tuberculosis. Two active cases met source case criteria; the yield was 0.9 (2 of 207) source cases per 100 children investigated. Of 312 non-household contacts, 57 (18%) were infected and none had the disease.

Conclusions: Although few source cases were identified for young tuberculin skin test reactors in New York City, investigations identified a proportion of cases and infection in associates similar to that identified among contacts to pulmonary tuberculosis cases. Such investigations may be identifying a high-risk group and should be considered, depending on program resources.