TORONTO -- A study has shown that a new rapid tuberculosis test can change treatment in Nunavut, where rates of the disease are among the highest in the country.
Next-day results are now available, whereas it previously took at best a week, and often several, to diagnose the disease.
That allows doctors to put infected -- and contagious -- people on treatment far faster, which is better for their health and for the health of the people with whom they come in contact.
Nunavut's TB rate is about 50 times that of the Canadian average.
Dr. Gonzalo Alvarez says in each of the past four to five years, Nunavut has had between 80 and 100 active TB cases out of a population of about 37,000. Ottawa, with a population of about 1.3 million people, has about half that number of cases a year.
Despite that, the territory does not have a laboratory that can do TB testing; previously all samples were being sent to Ottawa.
But a study Alvarez and some colleagues recently published shows the rapid test is about 85 per cent successful at detecting TB in people who have it. That is actually more effective than the current first-line test, called smear microscopy.
"To be able to have someone come in to my clinic and for me to suspect that they might have tuberculosis and to be able to definitely tell them whether they have tuberculosis or not by the next day is a really big improvement," says Alvarez, a respirologist and scientist at the Ottawa Hospital Research Institute. Alvarez does research in Nunavut.
Traditionally, people who are suspected of having active tuberculosis are asked to produce a sample of sputum, mucus coughed up from the lungs.
Smear microscopy involves looking for TB bacteria under a microscope. But the test isn't terribly accurate. If the results come back negative, it's not a guarantee that the person is free from infection.
The best test involves trying to grow bacteria from the sputum sample. But Mycobacterium tuberculosis, the bug that causes the disease, grows very slowly. Getting an answer can take weeks.
The new test looks for the DNA of the bacteria in the sputum sample. The equipment needed to run the test is about the size of a computer hard drive, Alvarez says. He calls it "a lab in a box."
A Toronto-based TB expert applauded the findings, but noted it would be better if the test were more sensitive. Dr. Michael Gardam says that with an 85 per cent sensitivity rate, doctors will still have to wait for smear tests -- and maybe culture results -- on 15 per cent of the suspected cases.
"So you're still stuck waiting for the culture," said Gardam, who is director of infection prevention and control for the University Health Network, a conglomeration of four University of Toronto teaching hospitals.
The test is called Xpert MTB/RIF and is made by Cepheid Inc., of Sunnyvale, Calif. The study was funded by the Canadian Institutes of Health Research.
