Guidelines

Many countries have developed guidelines which incorporate the use of interferon gamma release assays (IGRA) such as T-SPOT.TB. The information below is provided as an abbreviated guide to these guidelines. However, we recommend you read the guidelines appropriate for your country.

On 24 March 2011, The National Institute for Health and Clinical Excellence (NICE) published their new clinical Guidelines for TB control in England and Wales. 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'.

In recognition of the mounting clinical evidence in favour of IGRA technology, the new guidelines recommend going straight to an IGRA test in a number of specified indications including: 

• In an outbreak situation when large numbers of individuals may need to be screened
• Recent arrivals from high incidence countries who are from 16 to 34 years old (older subjects may also be screened depending on the risk/benefits of treatment
• The immunocompromised and some HIV subjects
• New NHS employees who have recently arrived from high incidence countries or who have had contact with patients in a setting where TB is highly prevalent
• Hard to reach populations

In addition, the new guidelines recommend that an IGRA test be considered for initial use in individuals for whom Mantoux testing may be less reliable, such as those who have been BCG vaccinated, and for use in individuals whose Mantoux test result is positive.

If your laboratory is in the UK and is not yet able to provide a blood test, then send your samples to Oxford Diagnostic Laboratories National TB Testing Services.

In November 2005 the Swiss Lung Association released recommendations for the diagnosis of TB infection in contact investigations using blood tests in Bulletin 45/10 of the Office Federal de la Sante Publique. The main points are: 

• Confirm a positive Mantoux tests with an IGRA
• Use only an IGRA in immunocompromised subjects
• Children are excluded from being tested with IGRA

In December 2007 the following guidelines were released for the use of IGRA to screen patients prior to administration of anti-TNF alpha therapies.  

• All patients should be screened for LTBI before being given anti-TNF alpha therapies
• Screening should be based on history, chest x-ray and IGRA (TST is no longer recommended)
• Preventive treatment should be given where LTBI is suspected as a result of:
  •  Positive IGRA
  •  Abnormal x-ray suggesting TB which was not adequately treated
  •  History of significant prior exposure

Recommendations for the identification of LTBI were released jointly by the Associazione di Microbiologia Clinica Italiana (AMCLI) and the Federazione Italiana per le Malattie Polmonari Sociali e la Tubercolosi (FIMPST) in May 2006. The main points are: 

• Mantoux testing should be carried out and where positive an IGRA should be performed
• In subjects with an expected TST positivity rate of 40% or more, and in immunosuppressed patients an IGRA should be carried out without a prior TST
•  IGRA may be used along with other tests in the diagnosis of active disease

Dutch guidelines for contact tracing and screening were released in February 2008. The main points are: 

• Carry out a Mantoux test and where the subsequant induration is more than 5mm perform an IGRA.
•  In subjects where the Mantoux “may be less reliable” perform an IGRA without a prior Mantoux.
• IGRA can be used in place of a Mantoux in the work up for active disease diagnosis

The Haute Autorite de Sante issued preliminary guidelines in December 2006 suggesting that IGRA tests should be used in the following settings: 

• Contact tracing in subjects older than 15 years
• Health care workers where a TST may not be reliable
• To assist in the diagnosis of active disease, particularly non-pulmonary
• Pre-TNF alpha therapy screening

Draft guidelines published in July 2008 proposed that IGRA can be used in the following settings: 

• Contact tracing (in conjunction with a TST)
• In certain circumstances IGRA, if available can be considered as the sole test for LTBI:
  • Where the TST may be falsely negative due to immunosuppression
  • When screening large numbers of individuals as part of a public health investigation
•  Pre-employment screening of healthcare workers
• For individuals, commencing immunosuppressive therapy e.g. TNF-α antagonists