Rapid blood tests which are used by the NHS are unable to rule out tuberculosis (TB). They should be replaced with a newer, more accurate blood tests, according to a study from Imperial College London.
TB is a bacterial infection which affects the lungs and is spread by droplets from the coughs and sneezes of infected patients. It causes a cough, weight loss and fevers. Early treatment and diagnosis is essential for both the health of the individual patient and to prevent the spread of the infection to others. This means there is a need for rapid, convenient blood tests to rule out a diagnosis in suspected cases.
The current blood tests
The rapid tests which are currently available to the NHS are known as interferon-gamma release-assays (IGRAs). These can indicate if a patient has a TB infection by detecting their immune response to TB bacteria based on a blood sample. The findings are then confirmed with cultured patient samples in the laboratory.
In the study co-led by Professor Onn Min Kon of Imperial College Healthcare NHS Trust, researchers compared the existing IGRA tests which are commercially available with new generation tests in 845 patients with suspected TB in 10 NHS hospitals in England.
The analysis revealed that the second-generation blood tests have a 94 percent diagnostic sensitivity in patients with a confirmed case. This means they give a positive result for 94 percent of patients with infection. This is statistically significantly higher than either of the currently commercially available IGRA tests (ranging between 67.3 percent and 81.4 percent).
Saving the NHS money
The findings indicate the test would be much more accurate at ruling out TB infection in suspected cases, so saving time and resources and enabling patients to receive treatment more rapidly.
Professor Ajit Lalvani, Chair in Infectious Diseases at the National Heart & Lung Institute at Imperial College London, who led the study, said: “Tens of thousands of patients undergo diagnostic assessment for symptoms suggestive of TB, resulting in over 5,000 cases of TB diagnosed each year. Stopping the use of the existing, inadequate tests could save the NHS a lot of money. In contrast, the new, more accurate rapid blood test, will improve and accelerate diagnostic assessment of patients with suspected TB.”