Can a urine test identify TB?
Urinary compound may also track treatment response
SAN DIEGO -- A substance found in urine appears able to distinguish between people with and without tuberculosis, a researcher said here.
And a prospective case-control study suggests that, in those with confirmed TB, it also appears to diminish as treatment progresses and the disease is cured, according to Flonza Isa, MD, of Weill Cornell Medical College in New York City.
If the results are confirmed, the substance -- dubbed simply Compound 490 -- could form the basis of inexpensive, non-invasive TB testing at the point of care, Isa reported at the annual IDWeek meeting, held jointly by four medical organizations with an interest in infectious illness -- the Infectious Diseases Society of America (IDSA), the HIV Medicine Association (HIVMA), the Society for Healthcare Epidemiology of America (SHEA), and the Pediatric Infectious Diseases Society (PIDS).
Such a test is badly needed, Isa said, because current ways of diagnosing TB -- smear microscopy, culture, or polymerase chain reaction (PCR) testing are inaccurate, slow, or expensive.
And with an estimated 9 million new infections and 1.5 millions deaths around the world every year, better therapy for TB -- starting with better diagnosis -- is important, Isa said.
"We need a urinary biomarker or any real biomarker for TB because it's a disease that is notoriously hard to diagnose," commented Amesh Adalja, MD, of the University of Pittsburgh Medical Center and a spokesman for the IDSA.
It's also difficult to judge the progress of treatment, he told MedPage Today, so a biomarker that helped in both areas would markedly improve both diagnosis and therapy.
Indeed, the study suggests that Compound 490 is functioning "as you'd want an ideal biomarker to perform," he said.
But Adalja cautioned that the study is preliminary. "There's a lot more work that needs to be done -- they actually need to identify what this biomarker is, how well it holds up in all different types of populations, what happens in different scenarios," he said.
The first question is high on the research agenda, Isa said.
She and colleagues used a method called high-performance liquid chromatography-coupled time of flight mass spectrometry, which separates substances in a sample by weight but does not actually identify them.
So the researchers know that Compound 490 has a molecular weight of 490 -- hence the name -- but don't know yet what it is or whether it is a product of the TB or a result of some host immune process, she said.
What they do know is that it was quite reliable in distinguishing between people with TB confirmed by other methods and controls who did not have the disease.
To find the compound in the first place, she and colleagues worked with the Gheskio centers in Port-au-Prince, Haiti, which treat some 2,100 TB patients a year. The Caribbean nation has the highest TB rate in the Americas, at 254 per 100,000 people.
The researchers identified 102 people with active TB (defined by chest radiography, sputum smear for acid-fast bacilli, or TB culture) and matched them with 102 controls by age, sex, and HIV status.
The participants had an average age of 34 and 52% of them were male, Isa reported, with the only significant difference between the groups being that the TB patients weighed about 26 pounds less on average than the controls.
They collected urine samples at enrollment from all participants, which for cases meant before treatment was started. As well, they collected urine samples from a subset of cases several times during the first 3 months of therapy.
A three-stage analysis eventually showed that only Compound 490 was significantly different in samples from cases and controls, at P=0.0001, with an average abundance of 54,896 counts in cases versus 7,545 counts in controls.
The area under the receiver operating characteristic curve -- a measure of how well a test discriminates between samples -- was 0.991, where an area of 1.0 would represent a perfect test, Isa reported.
Importantly, she said, the relative abundance of the compound fell over time in the 28 patients who were followed longitudinally for 3 months.
The study had support from the NIH. Isa made no disclosures.
Primary Source: IDWeek
Source Reference: Isa F, et al "A novel urinary biomarker of tuberculosis and response to chemotherapy" IDWeek 2015; Abstract 101.
Source: MedPage Today
