TB blood test promises cheap, quick results
[DHAKA] Bangladeshi scientists have developed a cheap, 30-hour tuberculosis (TB) test based on blood samples rather than sputum.
The 'antibodies in lymphocyte supernatant' (ALS) test was developed by a team at the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B), whose members say it can even detect forms of TB that are difficult to diagnose. It has earned the ICDDR,B its first patent.
"If our body is infected by TB or any other germs, it responds automatically by producing antibodies," Rubhana Raqib, who led the team, told SciDev.Net. While some diseases are easily treated in this way, it has proven difficult to test in active tuberculosis as most people carry the background antibodies.
Raqib and colleagues developed the test in 2001 and have been improving it ever since.
At least four other TB tests are widely used in Bangladesh and elsewhere: chest X-rays; sputum smear microscopy; culturing Mycobacterium tuberculosis, the pathogen that causes the disease, from either sputum or the site of infection; and the polymerase chain reaction, which amplifies and identifies the pathogen's DNA from the patient's sputum or the site of infection.
The sputum culture method is the most reliable way of diagnosing TB, but it is expensive, takes four to five weeks, and requires special equipment and biosafety measures.
The ALS test is therefore a major breakthrough, Raqib claimed. According to the WHO, more than 300,000 people in Bangladesh are infected with TB each year and 70,000 die from it.
But the ALS test also needs special equipment. "Hospitals in Bangladesh are not adequately equipped yet. So it is not possible to introduce this method until they have the proper laboratory facilities," Raqib said.
Asif Mujtaba, a tuberculosis specialist at the National Institute of Diseases of the Chest & Hospital (NIDCH), Bangladesh's biggest TB hospital, said: "This method of testing is an addition [to existing detection methods]. But this method works better for children." This is because children do not show typical clinical symptoms of TB, ruling out some diagnosis methods.
Alexander Yule, a UK-based consultant who has studied TB diagnostic tests, compared the ALS test with the DNA test developed by Cepheid and recently endorsed by the WHO. "[The] DNA test is less complicated because Cepheid has spent a great deal on R&D [research and development] to simplify testing and to remove the need for scrupulous sample processing, hence the very high unit cost," he said.
"ALS is physically and technically simpler [but it] still needs validation in larger and more challenging patient populations."
Raqib said: "We have already trained a group of researchers in Rwanda on how to test [for] TB using [the] method, and we have just completed research in Ethiopia on co-infected patients in collaboration with Swedish and African scientists".