IGRA in HIV+ patients

USEFULNESS OF INTERFERON-GAMMA RELEASE ASSAYS IN THE DIAGNOSIS OF TUBERCULOSIS INFECTION IN HIV-INFECTED PATIENTS IN BULGARIA

R. Markova1, Y. Todorova1, R. Drenska1, I. Elenkov2, M. Yankova2, D. Stefanova3
National Center of Infectious and Parasitic Diseases, Department of Immunology and Allergology, Sofia, Bulgaria1
Infectious Diseases Hospital “Prof. Ivan Kirov”, AIDS Clinic, Sofia, Bulgaria2
University Hospital for Lung Diseases “St. Sofia”, TB Clinic, Sofia, Bulgaria3
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ABSTRACT
We aimed to evaluate the usefulness of incorporating the result from an IFN-gamma release assay (IGRA) in the algorithm for initial diagnosis of tuberculosis (TB) in prospectively enrolled HIV-infected subjects. Ninety HIV-infected subjects with clinical and/or radiological features consistent with a possible diagnosis of active-TB were tested with QuantiFERON®-TB Gold In-Tube (QFT) and T-SPOT.TB™ (SPOT). All information, including IGRA results, was available to clinicians for making their diagnosis. Those diagnosed with TB were given anti-TB treatment and samples were collected for microbiological culture.

Overall, 35/90 patients were QFT positive and 30/90 by SPOT. QFT was indeterminate for 5/90 subjects (5.5%) and SPOT for 11/90 (12.2%; p=0.0313). Active-TB was microbiologically confirmed in 13 subjects and twelve (92%) were positive by QFT and one was negative. For SPOT, 8/12 (62%; p=0.125) were positive, one- negative, and 4 were indeterminate. Of the 77 HIV-positive subjects without microbiologically confirmed active-TB, 23 (30%) were positive, 49 (64%) negative, and 5 (6%) indeterminate by QFT, compared with 22 (29%), 48 (62%) and 7 (9%) by SPOT. Those IGRA positive, and two who were IGRA indeterminate, had a final presumptive diagnosis of active-TB, based upon initial clinical symptoms and improvement with anti-TB treatment. All IGRA negative subjects had a diagnosis other than tuberculosis and none have since developed active TB over a period of more than 12 month.

In conclusion, both IGRAs provided useful additional information for assisting the diagnosis and early treatment of Mycobacterium tuberculosis infection in immunocompromised HIV/AIDS patients with negative smear microscopy. A positive IGRA result was a significant factor in making initial diagnoses of TB, diagnoses that were later supported by clinical outcome following anti-TB therapy, and diagnoses other than TB in those IGRA negative. The QFT and SPOT tests had similar high sensitivity, with QFT having fewer indeterminate results, in our HIV-infected immunocompromised population