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QuantiFERON conversion following tuberculin administration is common in HIV infection and relates to baseline response.

QuantiFERON conversion following tuberculin administration is common in HIV infection and relates to baseline response.
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Esmail H, Thienemann F, Oni T, Goliath R, Wilkinson KA, Wilkinson RJ,


Esmail H, Thienemann F, Oni T, Goliath R, Wilkinson KA, Wilkinson RJ, (click to view)

Esmail H, Thienemann F, Oni T, Goliath R, Wilkinson KA, Wilkinson RJ,

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BMC infectious diseases 2016 Oct 716(1) 545

Abstract
BACKGROUND
HIV-1 infection impairs tuberculosis (TB) specific immune responses affecting the diagnosis of latent TB. We aimed to (1) determine the proportion of HIV-1-infected adults with a negative QuantiFERON®-TB Gold in-tube (QFT-GIT) and Tuberculin skin testing (TST) that convert to QFT-GIT positive following TST, and (2) evaluate the relationship between conversion and baseline QFT-GIT results.

METHODS
HIV-1 infected adults being screened for a TB vaccine study in South Africa underwent QFT-GIT followed by TST. As per protocol, QFT-GIT was repeated if randomization was delayed allowing for evaluation of TST boosting in a proportion of participants.

RESULTS
Of the 22 HIV-1 infected, TST and QFT-GIT negative adults (median CD4 477/mm(3) IQR 439-621) who had QFT-GIT repeated after median 62 days (IQR 49-70), 40.9 % (95 % CI 18.6-63.2 %) converted. Converters had a significantly greater increase in the background subtracted TB antigen response (TBAg-Nil – all units IU/mL) following TST, 0.82 (IQR 0.39-1.28) vs 0.03 (IQR -0.05-0.06), p = 0.0001. Those who converted also had a significantly higher baseline TBAg-Nil 0.21(IQR 0.17-0.26) vs 0.02(IQR 0.01-0.07), p = 0.002. Converters did not differ with regard to CD4 count or ART status. ROC analysis showed a baseline cut off of 0.15 correctly classified 86.4 % of converters with 88.9 % sensitivity.

CONCLUSIONS
Our findings support the possibility that there are 2 distinct groups in an HIV-1 infected population with negative QFT-GIT and TST; a true negative group and a group showing evidence of a weak Mtb specific immune response that boosts significantly following TST resulting in conversion of the test result that may represent false negatives. Further evaluation of whether a lower cut off may improve sensitivity of QFT-GIT in this population is warranted.

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