Dan Gregson was co-author of the paper, "Lyme Disease: How Reliable are Serologic Results?"
Riley Brandt, University of Calgary
Sept. 1, 2015
Some U.S. labs test inaccurately for Lyme disease, doctors warn
Canadians seeking a second opinion on their symptoms may receive false-positives, article cautions
Lyme disease is becoming increasingly common in Canada, and Canadians with Lyme disease symptoms may seek diagnoses from laboratories in the United States, although many of the results will be false-positives, according to a commentary from a Cumming School of Medicine expert, published Monday in a Canadian Medical Association Journal article.
“Patients with chronic subjective symptoms without a diagnosis can be vulnerable and desperate for an answer as to the cause of their illness," writes Dr. Dan Gregson, divisions of Medical Microbiology and Infectious Diseases, departments of Pathology and Laboratory Medicine, and Medicine, at the University of Calgary’s Cumming School of Medicine, with co-authors. "Giving them a false diagnosis based on flawed testing is misleading." Read the full report.
Canadians with nonspecific symptoms such as joint pain, fatigue and mental fog may turn to commercial laboratories in the U.S. because they suspect they may have Lyme disease. Many of these laboratories use only a single test that relies on nonevidence-based interpretation, such as the Western blot test. A positive test result that relies solely on Western blot testing is most likely a false-positive, or a test result that indicates a condition or finding that doesn't exist.
Recent research has found false-positive results in people without Lyme disease at three of four commercial U.S. laboratories (ranging from 2.5 per cent to 25 per cent), with a rate of more than 50 per cent of false-positives at one lab.
Tests at the National Microbiology Laboratory of Canada, which uses guidelines from the U.S. Centers for Disease Control and Prevention, are as sensitive as those used in specialty U.S. laboratories.
“Patients and physicians should be cautious in choosing a referral laboratory in the U.S. when seeking ‘second opinion’ serology after receiving a negative test result in Canada,” write the authors. “Laboratories that use the standard CDC two-tier testing algorithms should be preferred over those that report results based on unproven, unvalidated, in-house criteria.”
Patients who are experiencing Lyme disease-like symptoms should receive a complete evaluation to determine the cause of their symptoms.