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Am J Respir Crit Care Med. 2015 Aug 1;192(3):367-73. doi: 10.1164/rccm.201501-0199OC.

T-SPOT.TB Interferon-γ Release Assay Performance in Healthcare Worker Screening at Nineteen U.S. Hospitals.

Author information

1
1 Department of Pathology and Laboratory Medicine, St. Vincent Hospital, Worcester, Massachusetts.
2
2 Occupational Health Services, Detroit Medical Center, Detroit, Michigan.
3
3 Occupational Health Services, Massachusetts General Hospital, Boston, Massachusetts.
4
4 Department of Medicine, Employee Health Services and Occupational Injury Care and Wellness, UMass Memorial Health Care, Worcester, Massachusetts.
5
5 Division of Occupational Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland.
6
6 Occupational Health Services, St. David's Medical Center, Austin, Texas.
7
7 Occupational Medicine, St. Francis Hospital, Indianapolis, Indiana.
8
8 Health, Safety and Environment, Johns Hopkins Health System and University, Baltimore, Maryland.
9
9 Employee Health, Medical City Hospital, Dallas, Texas.
10
10 Risk Management/Occupational Health, Sonora Regional Medical Center, Sonora, California.
11
11 Employee Health, Baptist Health Louisville, Louisville, Kentucky.
12
12 Oxford Immunotec, Marlborough, Massachusetts; and.
13
13 Veristat LLC, Holliston, Massachusetts.

Abstract

RATIONALE:

Interferon-γ release assays have significant advantages over tuberculin skin testing in many clinical situations. However, recent studies have called into question their reliability in serial testing of healthcare workers because of reportedly high rates of positivity and high conversion/reversion rates on retesting.

OBJECTIVES:

To define the performance characteristics of the T-SPOT.TB test, an interferon-γ release assay, during serial screening programs of healthcare workers at 19 U.S. hospitals.

METHODS:

A total of 42,155 T-SPOT.TB test results from healthcare workers at 19 geographically diverse hospitals obtained for routine tuberculosis screening programs were analyzed to determine the rates of positivity, reversion, and conversion in serial testing data.

MEASUREMENTS AND MAIN RESULTS:

In 19,630 evaluable serial pairs from 16,076 healthcare workers, the mean test positivity rate was 2.3% (range, 0.0-27.4%). The mean conversion rate was 0.8% (range, 0.0-2.5%), and the mean reversion rate was 17.6%. Positivity and conversion rates correlated with known tuberculosis risk factors including age and sex. The observed specificity of the T-SPOT.TB test was at least 98.6%.

CONCLUSIONS:

The high concordance and test completion rates in this study suggest that the T-SPOT.TB test is a reliable tool for healthcare worker serial screening. As expected, the observed positivity rates were lower compared with the tuberculin skin test, likely reflecting the higher specificity of this test. Furthermore, the observed rates of conversion were low and significantly correlated with the geographic incidence of tuberculosis. Our findings suggest that the T-SPOT.TB test is an accurate and reliable way to screen healthcare workers.

KEYWORDS:

LTBI; conversion; reversion; serial testing; tuberculosis screening

PMID:
26017193
DOI:
10.1164/rccm.201501-0199OC
[Indexed for MEDLINE]

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