A study led by researchers from the NIHR Imperial BRC and NIHR HPRU in Re`spiratory Infections has found that rapid blood tests used by the NHS are unable to rule out tuberculosis (TB) and should be replaced with a new, more accurate test.
TB is a bacterial infection affecting the lungs, which is spread through droplets in coughs and sneezes from infected individuals. Early diagnosis and treatment is essential for the health of the patient as well as for preventing the spread of TB to others. Rapid, accurate and convenient tests are therefore required to confirm or rule out TB diagnosis in suspected cases.
In the largest study to date of rapid TB tests used by the NHS, the researchers found that the commercially available tests currently used are not sensitive enough to rule out a diagnosis of TB, and so have limited clinical use.
In the study, published in the journal Lancet Infectious Diseases, Prof Ajit Lalvani and Prof Onn Min Kon compared these existing tests against a new second generation rapid blood test, developed at Imperial. Blood samples from 845 patients with suspected TB were collected from 10 NHS hospitals in England, analysed using both sets of tests and benchmarked against a confirmed diagnosis based on positive culture results.
The 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 tests (which range from 67.3% and 81.4%). These findings indicate the test would be much more accurate at ruling out TB infection in suspected cases of TB, saving time and resources and enabling patients to receive treatment more rapidly.
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 Lalvani, Chair in Infectious Diseases at the National Heart & Lung Institute at Imperial College London, 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.”
According to the researchers, the medical need for better TB diagnostics is so high that despite a lack of evidence to support their use in patients with suspected TB, existing tests are widely used in clinical practice in the UK and other developed countries. They add that stopping use of the existing tests could 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.
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