Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1402 page)

   Initial TST indeterminate or equivocal test result is seen in patients in whom TB cannot be ruled out by other factors.

   Special Collection and Transport Instructions

   Specimens must be collected into tubes specified by the manufacturer.

   Specimens must be collected strictly following the manufacturer’s instructions.

   Specimens must be inverted or shaken vigorously according to the manufacturer’s instructions.

   Transport at room temperature. Specimens should not be refrigerated or frozen during transport.

   Interpretation

   
Expected results:
Negative.

   
Positive results:
Positive results suggest that infection with
M
.
tuberculosis
is likely, but cannot determine the stage of infection. Reactive specimens support a diagnosis of acute, active or, latent infection, or reactivation TB.

   
Negative results:
Infection with
M
.
tuberculosis
is unlikely.

   
Indeterminate or borderline:
M
.
tuberculosis
infection is not established. Alternative or sequential testing may resolve the diagnosis.

   Limitations

   The performance of IGRAs has not been adequately evaluated in certain patient populations, like pregnant women, children, patients with malignancies and other chronic infections, patients treated with medications that affect immune response, and patients with extended therapy with antituberculous agents.