Research to Improve the Detection and Treatment of Latent Tuberculosis Infection: Diagnostics

Is a new skin test (C-Tb) a useful and cost effective way of diagnosing latent tuberculosis in the UK?

What is this study about?

RID-TB: Dx is a randomised controlled trial to evaluate a RD-1 based C-Tb skin test diagnostic strategy for detection of latent tuberculosis (TB) infection and initiation of TB preventive treatment in the UK.

The trial aims to improve how latent tuberculosis infection (LTBI) is identified within the NHS. People with latent TB have been infected with the bacteria that cause tuberculosis (TB), but are not ill and do not have any symptoms. Identifying people with latent TB and starting them on anti-TB medications can prevent them developing active TB, which is infectious and requires a longer treatment period.  

The main study will investigate whether a new latent TB skin test, called C-Tb, can be offered as an alternative to the standard interferon gamma release assay (IGRAblood test to diagnose LTBI.

C-Tb is as accurate as the IGRA blood test (which provides results in 1-4 weeks), but is conducted, and the results checked, in the exact same way as the current skin test, which quickly delivers results in 2-3 days. The study will assess how use of the test affects LTBI care. Although the study is a randomised controlled trial (RCT), enrolled participants will have an IGRA test if they would prefer not to have the C-Tb test, or if they are not eligible to receive the C-Tb test.

A small pilot study will explore whether it is possible for the C-Tb skin test to be read remotely, using a supported video call with the study team. If these remote reads are as accurate as the skin test being read in the clinic, then the option to have a remote appointment, rather than attending the clinic in person, will be offered for the remainder of the study.  

We will also look at how people feel about LTBI, including how they feel about the C-Tb test and whether they decide to receive the test if it is offered to them, in an optional behavioural sub-studySome people may also be invited to a short (15-20 minute) recorded interview, to talk in more depth about their views on the LTBI tests.  

We are also analysing how much it costs people to come to the clinic for the appointments alongside other health service use data, using an optional health economics sub-study that will allow us to see if the C-Tb test offers value for money for the NHS.

Type of study

Randomised trial

Contact details


Who is funding the study?

RID-TB: Dx is a part of a 5-year programme of work, RID-TB, which is funded by the National Institute of Health and Care Research (NIHR).

When is it taking place?

2018 - 2024

Where is it taking place?

RID-TB: Dx will recruit patients from hospitals, GP practices and community settings (e.g. temples) in London, UK.

Who is included?

Adults who are eligible for NHS LTBI screening.