Received February 29, 2008
Accepted on April 16, 2008

ORIGINAL ARTICLES

Interferon- Release Assays for Diagnosing Mycobacterium tuberculosis Infection in Renal Dialysis Patients

Kevin L. Winthrop ^*||1, Melissa Nyendak , Helene Calvet , Peter Oh ^||, Melanie Lo ^||, Gwendolyn Swarbrick , Carol Johnson , Deborah A. Lewinsohn , David M. Lewinsohn , and Gerald H. Mazurek ^*

*Division of Tuberculosis Elimination, National Center for HIV, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia; Oregon Health and Science University and the Portland VA Medical Center, Portland, Oregon; Long Beach Department of Health and Human Services, Long Beach, California; and ||Division of Communicable Disease Control, California Department of Health Services, Richmond, California

¹ To whom correspondence should be addressed. E-mail: Winthrop{at}ohsu.edu.

	Abstract

Background and objectives: End-stage renal disease (ESRD) patients are at high risk for tuberculosis (TB). IFN- release assays that assess immune responses to specific TB antigens offer potential advantages over tuberculin skin testing (TST) in screening such patients for Mycobacterium tuberculosis infection. This study sought to determine whether IFN- release assay results are more closely associated with recent TB exposure than TST results.

Design, setting, participants, and measures: Prospective cohort investigation of patients at a hemodialysis center with a smear-positive case of TB. Patients without a history of TB underwent initial and repeat testing with TST, and with the IFN- assays QuantiFERON-TB Gold^® (QFT-G) and ELISPOT test. Outcome measures included the prevalence of positive test results, identification of factors associated with positive results, and test result discordance.

Results: A total of 100 (47% foreign born; median age, 55 yr; age range, 18 to 83 yr) of 124 eligible patients were enrolled. Twenty-six persons had positive TST results, 21 had positive QFT-G results, and 27 had positive ELISPOT results. Patients with TB case contact were likely to have a positive QFT-G result (P = 0.02) and ELISPOT results (P = 0.04), whereas TB case contact was not associated with positive TST results (P = 0.7). Positive TST results were associated with foreign birth (P = 0.04) and having had a TST in the previous year (P = 0.04).

Conclusions: Positive IFN- assay results were more closely associated with recent TB exposure than were positive TST results. QFT-G and ELISPOT might offer a better method for detecting TB infection in ESRD patients.