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On 22 March 2006, The National Institute for Health and Clinical Excellence (NICE) published their Guidelines for TB control in England and Wales. The information here is provided as an abbreviated guide to the Guidelines. However, we recommend you read the Guidelines themselves for completeness. They are available online at www.nice.org.uk and are titled ‘Tuberculosis: clinical diagnosis and management of tuberculosis, and measures for its prevention and control’.

The NICE Guidelines recommend:

use of blood tests as the front line test for latent TB infection in preference to the skin test in all immunocompromised patients
use of blood tests as a secondary, confirmatory test in all cases when the tuberculin skin test (TST) is positive. The blood test is used as a means of screening out TST false positives
that the blood tests also have a role to play in the diagnosis of TB disease especially in non-pulmonary TB and as a rule-out test in TB suspects

If your laboratory is in the UK and is not yet able to provide a blood test, Oxford Immunotec also offer T-SPOT.Service.

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In October 2007, The Health Protection Agency published a position statement on the use of Inteferon Gamma Release Assay (IGRA) tests for Tuberculosis (TB), providing an update on the NICE guidelines descibing the use of IGRA's forTB control. The information here is provided as an abbreviated guide to this position statement. However, we recommend you read the document for completeness. It is available online at www.hpa.org.uk and is titled ‘Health Protection Agency Position Statement on the use of Inteferon Gamma Assay (IGRA) test for Tuberculosis (TB)’.

The main points are as follows:

Active disease

IGRAs should not be used for routine diagnosis of active TB but should be used when it has not been possible to confirm a diagnosis by culture and when radiological and histopathological evidence is lacking.

Latent Infection

In LTBI IGRAs are at least as sensitive at the TST and in BCG vaccinated populations are more specific. TST should be carried out first and those that are positive should be considered for IGRA testing if available. This would also apply to new entrant screening.

IGRAs should be the only test used in the following situations:

Where TST may be falsely negative due to immunosuppression
When screening a large number of people as part of a public health investigations since repeated visits would be impractical

Health care worker screening

New health care workers should be tested with IGRAs as they may come into contact with immunosuppressed patients and because of the logical simplicity of the tests.

Pre-TNF alpha screening

IGRAs may be a suitable alternative in BCG vaccinated subjects.

Switzerland

The Swiss Lung Association have also recommended confirming positive TST results with a blood test and indicate that either the blood test or the TST may be used as the initial test for immunosuppressed subjects.