Urine test for TB shows promise
[NEW DELHI] Testing urine samples for specific chemicals could serve as a quick and painless way to detect tuberculosis (TB), according to Indian researchers.
The urine test offers a less invasive diagnostic method for an infectious disease that causes three million deaths and 10 million new cases worldwide each year. Developing countries account for 95 per cent of new infections and 98 per cent of deaths.
The Delhi-based International Centre for Genetic Engineering and Biotechnology (ICGEB) and the Lala Ram Sarup Institute of Tuberculosis and Respiratory Diseases, collaborated with the National University of Singapore to develop the test.
The test measures five specific chemicals present in urine, the researchers reported last month (July) in Analytical Chemistry, published by the American Chemical Society.
TB diagnosis relies mainly on a test to detect Mycobacterium tuberculosis in blood or sputum samples taken from the lung and examined under a microscope.
Diagnostic tests based on 'serum' — the clear liquid separated from clotted blood — are not sensitive, especially in people vaccinated against TB.
Drug-resistant cases need an expensive, sophisticated test that takes two weeks of culturing blood samples to detect the bacterium.
Developing countries prefer a simple test requiring minimum resources and trained personnel, and one that gives quick and easily interpreted results, the Delhi scientists observed.
Their technique measures five 'volatile organic compounds' (VOCs) in urine that have a low boiling point and vaporise at room temperature.
The team tested the method in 117 fresh cases of TB and found significantly different levels of these chemicals in TB patients, compared with healthy people.
It found a distinct pattern — three VOCs showed higher levels and two lower levels — in TB patients, not seen in healthy persons or in patients with lung ailments such as lung cancer or asthma.
The levels could also indicate the effect of treatment, the team said.
"A major advantage of the proposed method is the non-invasive nature of urine collection. Urine is a comparatively safer matrix as compared to sputum and painless in collection as compared to blood," it added.
ICGEB scientist Ranjan Nanda, one of the authors of the paper, explained to SciDev.Net that this was the first stage.
Nanda's team plans to validate the findings from multiple sites across India and involve a larger number of patients using improved data acquisition methods.
The team also plans to profile other VOCs in urine samples “to identify the maximum number of molecules,” Nanda said.
Analytical Chemistry doi:10.1021/ac200265g (2011)