NICE has today published draft clinical guideline on diagnosing latent TB in children and adults.
The draft is a partial update of NICE’s 2006 guidelines and focuses on the diagnosis of latent TB using tuberculin skin tests - also known as Mantoux and Heaf tests - as well as the newer interferon-gamma tests.
The draft addresses which diagnostic strategy is most accurate in diagnosing latent TB in adults and children who: are recent arrivals from countries where TB is highly prevalent; have been in close contact with patients with active TB; and who are immunocompromised.
The original guidance recognised a lack of good quality evidence to show whether interferon-gamma tests are acceptable to patients and whether they are more effective than tuberculin skin tests for predicting subsequent development of active TB, or diagnosing or ruling out current active TB.
NICE recommended further research to compare the strategies of skin test only, skin test then interferon gamma test if positive, and interferon gamma test only. Concern was raised about the appropriateness of IGT use in current clinical practice during the planned review process for the original NICE guideline on the diagnosis and management of TB.
Based on a detailed analysis of this further research, the independent guideline development group concluded the relative benefit of IGT over TST in determining the need for treatment of latent TB infection is not certain - and in the case of younger children it feels that IGT may even perform less well.
However, the GDG has made recommendations in populations where they considered IGT to be of clear benefit, especially in cases where IGT would reduce the uncertain diagnosis of TST. Recommendations in the draft guideline therefore include:
To diagnose latent TB in:
Household contacts 5 years and older, non household contacts and adult contacts:
- A Mantoux test should be performed. Those with positive results (or in whom Mantoux testing may be less reliable) should then be considered for IGT.
Recent arrivals from highly prevalent countries aged 5 - 34 years:
- Offer a Mantoux test followed by IGT if positive.
Recent arrivals from highly prevalent countries aged 16 years and above:
- An IGT test alone can be used.
Recent arrivals from highly prevalent countries aged under 5 years:
- Use Mantoux as the initial test. If positive, taking into account BCG history, undertake clinical assessment to exclude active disease and consider treatment of latent TB.
People who are immunocompromised:
- For people with HIV and CD4 counts (also called T-cells, these are types of cells that help protect the body from infection) of less that 200, perform both an IGT test and a TST. If either test is positive assess for active TB. Consider treatment of latent TB if active disease is excluded.
- For people with HIV and CD4 counts of 200-500, perform an IGT test alone or and IGT test with concurrent TST. If either test is positive, assess for active TB. Consider treatment of latent TB.if active disease is excluded.
Dr Fergus Macbeth, director of the Centre for Clinical Practice at NICE, said: “If TB is left untreated it can be very serious or fatal but antibiotic treatments are highly effective. Up to 15% of adults with latent TB will go on to develop active TB at some point in their lives and the risk in children may be much higher. In people who are immunocompromised - for example, if they are HIV positive - the chance of developing active TB within five years of infection is up to 50%. Detection of latent TB is therefore important in controlling the disease.
He continued:”The newer interferon gamma tests for latent TB may offer some advantages over the current internationally recognised standard test - the Mantoux test. However, despite the studies that have been carried out since the original NICE TB guidance was published, important questions remain unanswered about the potential role of these new tests in clinical practice in the UK.
“The draft guideline therefore adopts a cautious, pragmatic approach by recommending that for many cases the most effective way to diagnose latent TB infection is a Mantoux test followed, depending on the result, by an IGT test.”
Stakeholders wishing to submit their comments on the draft guideline are invited to do so via the NICE website by 5 August 2010. NICE plans to publish its final guideline in December 2010.