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Application of Long-term cultured Interferon-γ Enzyme-linked Immunospot Assay for Assessing Effector and Memory T Cell Responses in Cattle
Published on: July 11, 2015
Interferon gamma release assays for detection of latent Mycobacterium tuberculosis in older Hispanic people
Julia M Scordo1, Génesis P Aguillón-Durán2, Doris Ayala3
1Host-Pathogen Interactions and Population Health Programs, Texas Biomedical Research Institute, San Antonio, TX, USA; The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
Background:
Interferon gamma release assays (IGRAs) are used to detect latent Mycobacterium tuberculosis (M.tb) infection (LTBI) in adults, but their performance in older people is not well-established. We evaluated IGRAs for LTBI detection in older Hispanic recent TB contacts (ReC) or community controls (CoC).
Methods:
Cross-sectional assessment of LTBI with T-SPOT.TB and/or QuantiFERON-Gold in-tube or -Plus assay in older (≥60 years) and adult (18-50 years) Hispanic people.
Results:
We enrolled 193 CoC (119 adults, 74 older persons) and 459 ReC (361 adults, 98 older persons). LTBI positivity increased with age in CoC (19%-59%, P<0.001), but was similar in ReC (59%-69%, P=0.329). Older people had lower concordance between IGRAs (kappa 0.465 vs 0.688 in adults) and more inconclusive results (indeterminate/borderline 11.6% vs 5.8% in adults, P=0.012). With simultaneous IGRAs, inconclusive results were resolved as positive or negative with the other IGRA. The magnitude of response to M.tb peptides in IGRAs was similar among age groups, but responsiveness to mitogens was lower in older people.
Conclusions:
IGRAs are suitable for LTBI detection in older people. Discordant and inconclusive findings are more prevalent in older people, but results are resolved when IGRA is repeated with a different IGRA test.
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