Background: Mtb infection is a major cause of morbidity and mortality in immunocompromised pts. Little is known about the performance of the available IGRAs in this population. We aimed to evaluate the utility of the QuantiFERON-TB Gold (QFT) and the T-SPOT.TBtests for diagnosing latent or active Mtb infections in cancer pts.
All available IGRA results, from 2011-2014, were evaluated and were correlated with concomitant Mtb infection diagnosed by AFB/culture when done for suspected cases. For pts with active Mtb infection, additional data on demographics, clinical characteristics, management and outcomes were collected from the medical records.
From a total of 808 IGRAs (512 T-SPOT.TB and 296 QFT), 60 (12%) T-SPOT.TB were invalid and 118 (40%) QFTs were indeterminate (figure). When screening for latent Mtb, the T-SPOT.TB performed better than the QFTs (179 T-SPOT.TB [96% negative, 3% positive, 1% borderline] and 122 QFT [62% negative, 3% positive, 34% indeterminate]). When IGRAs were done for suspected Mtb, 2 out of 18 (11%) pts who tested positive by T-SPOT.TB and 9 out of 17 (53%) pts who tested positive by QFT had active Mtb infection confirmed by culture. Of concern, 5 pts with active Mtb infection had negative (2) or indeterminate (3) QFT results. Of the 16 pts with active Mtb infection, the median age at time of diagnosis was 58 (range 22-76) and 4 pts had hematopoietic cell transplantation, 3 had leukemia, 5 had solid tumors and 4 did not have any underlying malignancy. Eight pts had pulmonary Mtb while 4 pts had extra-pulmonary Mtb (lymphadenitis (3), pelvic mass (1)), and 4 had more than one organ involvement. All patients received RIPE and only 10 completed therapy at a median duration of 6 months (range 1-11). No Mtb-attributable death occurred.
High rates of indeterminate QFT results were observed while T-Spot.TB. performed better in our cancer patients. Accurate diagnosis of latent and suspected Mtb in this patient population should be underscored given atypical presentations and significant morbidities.
F. El Chaer, None
E. Ariza-Heredia, Oxford Immunotec: Grant Investigator , Research grant
E. A. Graviss, None
V. E. Mulanovich, None
R. Chemaly, Oxford Immunotec: Consultant and Grant Investigator , Consulting fee and Research grant