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Causes of False Positive and False Negative Results for Tuberculosis Using the T-SPOT.TB Test

Description

The T-SPOT.TB Test is an interferon gamma release assay for tuberculosis. While interferon gamma release assays have advantages over the tuberculin skin test, false positive and false negative results may occur. Accurate diagnosis is important to avoid over or under treatment of a serious communicable disease.


Test: T-SPOT.TB from Oxford Immunotec in England

 

Causes of a false negative result:

(1) older age

(2) obesity (body mass index >= 25 kg per square meter)

(3) longer duration of illness prior to hospitalization (> 6 months)

(4) extrapulmonary tuberculosis (bone or joint infection, meningitis)

 

Causes of a false-positive result:

(1) "cured" tuberculosis (test may be unable to distinguish active current from past infection)


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