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Preferred Sample Type

Dedicated QuantiFERON-Gold IT samples (NIL, TB, MITO) available in all Trust Phlebotomy Departments, and available by request to Immunology Dept ext 42184).
Dedicated QuantiFERON-Gold Plus IT samples (NIL, TB1, TB2, MITO) available in all Trust Phlebotomy Departments, and available by request to Immunology Dept ext 42184).

Specimen Transport

Samples should arrive in laboratory on same day. No Friday service available.

Sample Processing in Laboratory

Lithium Heparin blood (5mls) may also be used, and transferred under aseptic conditions in the immunology Laboratory (by prior arrangement).

Turnaround Time

7 Days

Quantiferon Plus Interferon gamma release assay for TB

General Information

Quantiferon Plus IGRA test can be used to detect exposure to Mycobacterium Tuberculosis.

Special Collection Arrangements apply see section below on blood collection. This assay is currently only available within Heart of England NHS trust sites and by prior arrangement with the laboratory. Please contact the laboratory on 42184 to arrange. This assay is currently not available through Primary Care

The QuantiFERON-TB Gold Plus IT system uses four dedicated blood collection vacutainers containing specific M. tuberculosis proteins or controls (NIL, TB1,TB2, MITO tubes). Tubes are cultured overnight, and the amount of IFN-╬│produced is measured by enzyme linked immunoabsorption assay (ELISA).  Results for test samples are reported in International Units (IU) relative to a standard curve prepared by testing dilutions of manuracturer supplied IFN-╬│.

QuantiFERON TB Gold Plus IT is recommended for routine screening of all patients with normal lymphocyte counts, TB contacts, and healthcare worker pre-employment screening.

Patient Preparation

Blood Collection instructions

RESULTS - Positive, Negative, Borderline and Indeterminate results. 

Reference Range

A negative result suggests no active immune response to Mycobacterium Tuberculosis. A positive results indicates a response to MTB infection, but does not distinguish between active and latent disease. The test cannot be used to exclude active infection, since false-negative results do occur. It should always be interpreted in the context of other clinial and laboratory features.

Due to biological variations, re-testing borderline results is recommended. Indeterminate results indicate failure of positive or negative controls which may be due to technical or patient-specific factors.  Re-testing recommended.  


  • EQA Scheme?: Yes
  • EQA Status: Full EQA scheme