Determining the Indeterminate and Positivity Rates of the T-SPOT.TB Test in High-risk Populations

Background: Oxford Diagnostic Laboratories performed the T-SPOT.TB test on healthcare workers, patients and international students attending U.S. universities.

Objective: The objectives of this study were to determine the indeterminate and positivity rates of the T-SPOT.TB test in at-risk groups for tuberculosis infection.

Methods: Specimens were received by Oxford Diagnostic Laboratories, a CLIA and CAP certified laboratory, located in Marlborough, MA. Specimens were received from healthcare facilities and universities throughout the U.S. All samples were tested with the T-SPOT.TB test, an in vitro diagnostic test for the detection of tuberculosis infection. The reported sensitivity and specificity of the test is 95.6% and 97.1%, respectively.

Results: Between June 17, 2009 and October 31, 2009, 2923 specimens were tested by Oxford Diagnostic Laboratories. The positivity rate of the T-SPOT.TB test was 10.2%.  The T-SPOT.TB test indeterminate rate was 0.3%.  

Conclusions: The T-SPOT.TB test may be an effective replacement of the tuberculin skin test in the healthcare setting.