Positive: M. tuberculosis infection is likely.
Negative: M. tuberculosis infection is unlikely but cannot be excluded (especially if a patient is at high risk or has symptoms).
Indeterminate (QFT only) or Invalid (T-Spot only): The test did not provide enough information. Indeterminate and Invalid results indicate the test should be recollected for repeat testing.
Indeterminate or Invalid results may be due to:
- low lymphocyte count, reduced lymphocyte activity, or inability of the patient's cells to release IFN-γ (immune status factors)
- nonspecific IFN-γ circulating in the patient's blood or the presence of heterophile effects
- occurrence in patients with very low CD4 counts
- pre-examination, examination, or post-examination errors (technical factors)
Borderline or Equivocal (T-Spot only): Borderline results indicate the test result is valid but should be repeated with a new specimen. A TST may also be helpful in this case.
