New blood tests for TB could help accelerate diagnosis

New blood tests for TB could help accelerate diagnosis

Date: 21 January 2019

A new rapid blood test could enhance the way NHS doctors detect or rule out tuberculosis (TB), an NIHR-funded study has found.

The IDEA study, led by researchers at Imperial College London, is the largest of its kind to evaluate rapid TB tests used by the NHS, and the team compared new second generation rapid blood test to existing tests.

Researchers say that the new test, if implemented, could enable doctors to quickly detect or rule out TB infection and help them to distinguish patients who need further investigation and treatment from those who do not and pose no infectious risk to others. 

The study, funded by the NIHR’s Health Technology Assessment (HTA) Programme research has now been published in the journal Lancet Infectious Diseases.

TB is a bacterial infection affecting the lungs, causing cough, weight loss and fevers, and is spread through droplets from coughs and sneezes from infected patients.

Diagnosing and treating the condition early is essential for the health of the patient and for preventing TB spreading to others. Therefore, there is a need for rapid, convenient tests to rule out a TB diagnosis in suspected cases based on a blood sample.

While laboratory cultures of patient samples, such as sputum or invasive biopsies, are used to confirm the presence of the bacterium, the cultures can take several weeks. A negative result does not rule out a diagnosis of TB, as the bacteria cannot be cultured from samples in a large proportion of TB patients.

Currently available rapid tests for TB used by the NHS, known as interferon-gamma release-assays (IGRAs), can help to indicate if a patient has TB infection by detecting their immune response to TB bacteria based on a blood sample. The findings would then be confirmed with cultured patient samples in the laboratory.

Researchers compared existing commercially available IGRA tests against new generation tests in 845 patients with suspected TB in 10 NHS hospitals in England. Patient blood samples were analysed using both sets of tests, the results of which benchmarked against a confirmed diagnoses based on positive culture results.

Analysis of the rapid test results revealed that the second-generation test has a diagnostic sensitivity of 94% in patients with confirmed TB – meaning it gives a positive result for 94% of patients with infection – significantly and substantially higher than either of the existing commercially available IGRA tests (which range from 67.3% and 81.4%).

The study team say the findings indicate the test would be much more accurate at ruling out TB infection in suspected cases of TB, potentially saving time and resources and enabling patients to receive treatment more rapidly.

Researchers say that stopping use of the existing tests could potentially save the NHS over £2 million per year, with further savings likely generated by implementing the new tests – which could be available to health services within one to two years, pending regulatory approval.

The study was led by Professor Ajit Lalvani, Chair in Infectious Diseases at the National Heart & Lung Institute at Imperial College London.

More information on the study is available in the NIHR Journals Library.

  • Summary:
    A new rapid blood test could enhance the way NHS doctors detect or rule out tuberculosis (TB), an NIHR-funded study has found.
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