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In the largest study to date of rapid TB tests used by the NHS, a team led by researchers at Imperial College London found that available tests are not sensitive enough to rule out a diagnosis of TB in suspected cases, and so have limited clinical use.
The research looked at a new second generation rapid blood test, developed at Imperial, and found it to be substantially more accurate than the existing tests.
According to the team, once implemented the new test 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.
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.” 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 as well as for preventing the spread of TB to others.
There is therefore 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.