3rd International AIDS Society Conference on HIV Pathogenesis and Treatment Rio de Janeiro - July 24 - 27, 2005

EVALUATION OF AN ESAT-6 AND CFP-10 BASED WHOLE BLOOD IFN-γ ASSAY (QUANTIFERON-TB GOLD) FOR THE DIAGNOSIS OF TUBERCULOSIS AMONG TANZANIAN PATIENTS CO-INFECTED WITH HIV

IAS Conf HIV Pathog Treat 2005 Jul 24-27;3rd: Abstract No. TuPe7.1C09

Seshadri C.¹, Uiso L.O.², Diefenthal H.³, Asmuth D.A.⁴, Crump J.A.¹, Thielman N.M.¹, Bartlett J.A.^1
1Duke University Medical Center, Durham, United States of America, ²Kibong'oto National Tuberculosis Hospital, Sanya Juu, United Republic of Tanzania, ³Kilimanjaro Christian Medical Centre, Moshi, United Republic of Tanzania, ⁴University of California, Davis Medical Center, Sacramento, United States of America

INTRODUCTION: QuantiFERON-TB GOLD (QFTG) (Cellestis Inc, Carnegie, Australia) is a commercially available whole blood assay that measures IFN-γ response to stimulation with ESAT-6 and CFP-10, peptides specific for M. tuberculosis. We sought to evaluate its performance among patients with and without HIV infection.

METHODS: Adult inpatients were recruited from two hospitals in northern Tanzania between March and May 2004. Patients were evaluated with HIV serology, chest radiography, sputum for acid-fast bacilli, and tuberculin skin test (TST). Blood was processed for QFTG per manufacturer recommendations.

RESULTS: We enrolled 83 patients: median age 35 (20 to 82) years with 36 (43%) female and 29 (35%) HIV-infected. Two patients without chest radiographs were excluded from analysis. QFTG yielded indeterminate results in 10 (19%) of 53 HIV-uninfected and 13 (46%) of 28 HIV-infected patients. Among those with smear-positive pulmonary tuberculosis, TST was positive in 40 (100%) of 40 HIV-uninfected patients compared with 7 (54%) of 13 HIV-infected patients (p<0.001), and QFTG was positive in 28 (70%) of 40 HIV-uninfected patients compared with 3 (23%) of 13 HIV-infected patients (p=0.003). QFTG was less sensitive than TST in detecting patients with smear positive pulmonary tuberculosis among both HIV uninfected (p<0.001) and HIV infected (p=0.008) patients. Among five HIV-uninfected patients without clinical symptoms of tuberculosis, a normal chest radiograph, and a negative TST, QFTG was negative for 4 (80%).

CONCLUSIONS: The presence of HIV co-infection was associated with a significant reduction in sensitivity of both the TST and QFTG suggesting both are similarly limited by immune compromise. The high proportion of indeterminate QFTG and lack of sensitivity, particularly among HIV infected patients, may limit its applicability in settings like Tanzania. Larger studies in resource-poor areas with high rates of co-infection are required.

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050724
Clinical | TuPe7.1C09 | Chetan Seshadri
Tuberculosis

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