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High background rates of positive tuberculosis-specific interferon-? release assays in a low prevalence region of UK: a surveillance study

High background rates of positive tuberculosis-specific interferon-? release assays in a low prevalence region of UK: a surveillance study
High background rates of positive tuberculosis-specific interferon-? release assays in a low prevalence region of UK: a surveillance study
Background: Background rates of latent tuberculosis infection in low prevalence regions of Britain are unknown. These would be valuable data for interpreting positive IGRA results, and guiding cost-benefit analyses. The management of a large outbreak of tuberculosis occurring in a rural district hospital provided an opportunity to determine the background rates and epidemiology of IGRA-positivity amongst unselected hospital patients in a low-prevalence region of U.K.

Methods: As part of a public health surveillance project we identified 445 individuals exposed to the index cases for clinical assessment and testing by a TB-specific interferon-? release assay (IGRA): T-Spot.TB. Uniquely, an additional comparator group of 191 age-matched individuals without specific recent exposure, but with a similar age distribution and demographic, were recruited from the same wards where exposure had previously occurred, to undergo assessment by questionnaire and IGRA.

Results: Rates of IGRA positivity were 8.7% (95%CI, 4.2-13, n=149) amongst unexposed patients, 9.5%(3.0-22, n=21) amongst unexposed staff, 22%(14–29, n=130) amongst exposed patients, 11%(6.1-16, n=142) amongst exposed staff. Amongst the individuals without history of recent exposure to the outbreak, IGRA-positivity was associated with prior TB treatment (OR11, P.04) and corticosteroid use (OR5.9, P.02). Background age-specific prevalences of IGRA-positivity amongst unexposed individuals were: age <40 0%(N/A), age 40–59 15%(12–29), age 60–79 7.0%(1.1-13), age?80 10%(5.9-19).

Conclusions: Background rates of IGRA-positivity remain high amongst unselected white-Caucasian hospital inpatients in U.K. These data will aid interpretation of future outbreak studies. As rates peak in the 5th and 6th decade, given an ageing population and increasing iatrogenic immunosuppression, reactivation of LTBI may be a persistent hazard in this population for several decades to come.
1471-2334
1-6
Hinks, Timothy S.C.
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Varsani, Nimu
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Godsiff, David T.
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Bull, Thomas C.
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Nash, Katherine L.
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McLuckie, Lisa
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Maule, Catherine
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Flower, Tessa
acde7a26-4f28-4689-b028-f35d6e970548
Warley, Anthony
b46a5009-9521-4863-957e-970dc8f6af8e
Hinks, Timothy S.C.
14664ded-022f-47af-9d65-f49724a36e2f
Varsani, Nimu
e2eb9a1f-775d-46c9-ba72-0ac3631f24e1
Godsiff, David T.
1682eb82-5f97-4b8d-b349-cccdf015a6df
Bull, Thomas C.
1e4292dd-f3d8-4734-adb8-e9435d501d77
Nash, Katherine L.
4f1d98cc-aaa4-49a6-a68d-e7d42541f1d8
McLuckie, Lisa
4a5702f4-2a06-44eb-ab93-ddd89d913c3f
Maule, Catherine
426f5adc-a9af-4ec9-9722-bb1917fd5694
Flower, Tessa
acde7a26-4f28-4689-b028-f35d6e970548
Warley, Anthony
b46a5009-9521-4863-957e-970dc8f6af8e

Hinks, Timothy S.C., Varsani, Nimu, Godsiff, David T., Bull, Thomas C., Nash, Katherine L., McLuckie, Lisa, Maule, Catherine, Flower, Tessa and Warley, Anthony (2012) High background rates of positive tuberculosis-specific interferon-? release assays in a low prevalence region of UK: a surveillance study. BMC Infectious Diseases, 12 (339), 1-6. (doi:10.1186/1471-2334-12-339). (PMID:23216965)

Record type: Article

Abstract

Background: Background rates of latent tuberculosis infection in low prevalence regions of Britain are unknown. These would be valuable data for interpreting positive IGRA results, and guiding cost-benefit analyses. The management of a large outbreak of tuberculosis occurring in a rural district hospital provided an opportunity to determine the background rates and epidemiology of IGRA-positivity amongst unselected hospital patients in a low-prevalence region of U.K.

Methods: As part of a public health surveillance project we identified 445 individuals exposed to the index cases for clinical assessment and testing by a TB-specific interferon-? release assay (IGRA): T-Spot.TB. Uniquely, an additional comparator group of 191 age-matched individuals without specific recent exposure, but with a similar age distribution and demographic, were recruited from the same wards where exposure had previously occurred, to undergo assessment by questionnaire and IGRA.

Results: Rates of IGRA positivity were 8.7% (95%CI, 4.2-13, n=149) amongst unexposed patients, 9.5%(3.0-22, n=21) amongst unexposed staff, 22%(14–29, n=130) amongst exposed patients, 11%(6.1-16, n=142) amongst exposed staff. Amongst the individuals without history of recent exposure to the outbreak, IGRA-positivity was associated with prior TB treatment (OR11, P.04) and corticosteroid use (OR5.9, P.02). Background age-specific prevalences of IGRA-positivity amongst unexposed individuals were: age <40 0%(N/A), age 40–59 15%(12–29), age 60–79 7.0%(1.1-13), age?80 10%(5.9-19).

Conclusions: Background rates of IGRA-positivity remain high amongst unselected white-Caucasian hospital inpatients in U.K. These data will aid interpretation of future outbreak studies. As rates peak in the 5th and 6th decade, given an ageing population and increasing iatrogenic immunosuppression, reactivation of LTBI may be a persistent hazard in this population for several decades to come.

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Accepted/In Press date: 3 December 2012
Published date: 6 December 2012
Organisations: Faculty of Medicine

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Local EPrints ID: 352559
URI: http://eprints.soton.ac.uk/id/eprint/352559
ISSN: 1471-2334
PURE UUID: b968be10-d7c8-44a5-ab46-c215a37e1868

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Date deposited: 16 May 2013 11:32
Last modified: 19 Jul 2019 21:36

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Contributors

Author: Timothy S.C. Hinks
Author: Nimu Varsani
Author: David T. Godsiff
Author: Thomas C. Bull
Author: Katherine L. Nash
Author: Lisa McLuckie
Author: Catherine Maule
Author: Tessa Flower
Author: Anthony Warley

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