Is Lyme disease underdiagnosed or overestimated?
Ten years ago, most Canadians hadn’t heard of Lyme disease, a bacterial infection spread by a tick bite. But with 144 cases officially confirmed in Canada in 2009 and 707 cases in 2015, it’s on the rise.
Far more people think they should be counted in that number, but aren’t. Media articles abound featuring Canadians who have been diagnosed by US labs because they don’t trust the standard process for diagnosing Lyme in Canada.
But experts say that many people overestimate their Lyme risk and seek out treatment based on questionable results from unregulated US labs.
Is the alarm over Lyme disease warranted or overblown? Here’s what we know so far.
How Lyme disease is diagnosed in Canada
Lyme is spread by blacklegged ticks that are infected with the disease-causing bacteria, Borrelia burgdoferi. (Depending on the area, large or small percentages of the blacklegged tick population will be infected.) The only way to test for Lyme disease is to test for the antibodies that the body makes to combat this bacterium. Because it takes weeks for the antibodies to appear, the testing isn’t reliable in the initial stages of Lyme disease.
For this reason, guidelines from the Centres for Disease Control (which are used by doctors in Canada) advise doctors to immediately treat people if they’ve been in an area where Lyme disease is endemic and have a rash known as erythema migrans. Even if the rash isn’t present, the doctor can treat the patient without testing, if Lyme is highly suspected.
When Lyme is possible but not likely, health providers tend to first investigate other, more likely reasons for a person’s symptoms, such as influenza. “Often, if you don’t know what is causing a symptom like a fever, nothing is the right thing to do because it is likely a virus that will get better on its own,” explains Daniel Gregson, an infectious disease consultant with the University of Calgary and Alberta Health Services.
It’s important to note that the symptoms of Lyme disease, including muscle pain and arthritis, are common to many other – more likely – conditions. In one study, out of 297 people who had Lyme-like symptoms in a low-incidence region, only six tested positive, one of whom was found to have another condition that led to the positive antibody test.
But if no other diagnosis is found, and if Lyme-like symptoms persist, doctors can test. The tests are helpful in disseminated Lyme disease, when the bacterium has spread from the area around the bite to the rest of the body and the immune system is producing antibodies. This occurs anywhere from a few weeks to up to three months after a bite.
The first line of testing is the ELISA test. It picks up antibodies in disseminated Lyme disease 98% of the time (but misses them in 2% of cases). The problem with the ELISA test is that it has a high rate of false positives – the test diagnoses Lyme disease in 4% to 11% of patients who don’t actually have the disease. For this reason, another antibody test, the Immunoblot test is recommended after a positive ELISA result to confirm Lyme disease.
In general, the current testing protocol is accurate. This two-tier test approach has been reported to be 70% to 100% accurate in disseminated Lyme disease, depending on how early the test is done and how quickly a person develops antibodies. If a test comes back negative and it’s possible the test was done too early – within the first month or two since the onset of symptoms – it’s recommended that the person be tested again four to six weeks later, Gregson explains.
By the time someone has late-stage nervous system symptoms or Lyme-induced arthritis, the tests are 97% to 100% accurate. “Based on what we know, if you’ve been symptomatic for months, the tests we have in Canada should tell you whether you have Lyme disease,” says Todd Hatchette, an infectious disease doctor and professor at Dalhousie University.
Of course, for patients who have to wait weeks to have an answer for what can be debilitating symptoms, the tests aren’t good enough. “The longer you wait to be diagnosed, the longer the duration of disease, and the longer the recovery time,” says Doug Sider, medical director of communicable disease prevention and control at Public Health Ontario.
Controversies over missed Lyme diagnoses
Some patients worry that the Lyme-diagnosing criteria are too stringent. For one, the circular, expanding rash known as erythema migrans often doesn’t appear, says Marguerite Glazer, president of the Quebec Association of Lyme Disease. According to CDC data, 70% to 80% of patients who have Lyme disease will develop erythema migrans. But Glazer points to other studies that suggest less than half of people who get Lyme will notice a rash. (Hatchette says it’s possible the 70% to 80% number does not reflect real world situations, because people in studies may have been more closely monitored for signs of a rash.)
Secondly, Lyme advocates argue doctors only test when patients have been exposed to an ‘endemic’ area. “You can get Lyme disease anywhere,” says Glazer. That’s technically true, says Samir Patel, a clinical microbiologist in the Public Health Ontario Laboratory. Because Lyme-carrying ticks can travel on birds and other animals “there is no area in Ontario that is zero risk for Lyme disease.” (He argues, however, the likelihood of a person getting Lyme disease in a typical urban backyard would be a “freak occurrence.”)
Meanwhile, areas that have recently become endemic might not be marked on a Lyme surveillance map. Climate change is allowing blacklegged ticks to survive and breed for longer, as well as thrive in areas that used to be too cold. “We’re seeing a growth in tick numbers every year,” says Vett Lloyd, a biologist at Mount Allison University in Sackville, New Brunswick. And surveillance maps are always playing catch up, Lloyd explains. Typically, provincial public health officials find out about new endemic areas when people in these areas catch ticks on themselves and send them to their local public health units for testing.
Lyme advocates say doctors often don’t think of Lyme unless the erythema migrans rash is present or a patient is from an area where Lyme is known to be highly endemic, such as in certain southwest regions of Nova Scotia. “There’s this idea that unless you’ve been hunting or fishing, you can’t have Lyme disease,” says Jennifer Ringgard, a Montreal-based patient who paid a private lab in Canada for testing when her doctor refused to refer her because she never had a rash and hadn’t travelled to a Lyme-endemic area. (Gregson, says, however, that Ringgard’s experience is an exception – most doctors will order a Lyme test if a patient has persisting symptoms and is very concerned about Lyme, even if the disease is unlikely, he says.)
Actual cases of Lyme disease may be much higher than the official numbers. Patients who have been treated for Lyme after a rash without being tested aren’t always included in these numbers, Sider points out. Physicians are supposed to report these cases to local public health units but in Ontario, this often doesn’t happen, due to time constraints or a lack of awareness of their reporting duties, Sider explains. Meanwhile, those diagnosed in the US aren’t likely to be reported to Canadian public health agencies. And some Lyme disease patients might not be diagnosed or treated at all. In cases where a patient doesn’t report a rash, for example, doctors might not even consider the rare possibility of Lyme, and could instead diagnose patients with diseases that have similar symptoms.
“Physicians in low-risk areas would probably go years without seeing Lyme disease,” says Sider. “It’s a real challenge to get something that’s as infrequent as Lyme high enough in the minds of clinicians, whether family doctors, rheumatologists or infectious disease doctors.”
Meanwhile, for patients, Lyme can be too much on their minds. With the proliferation of inaccurate information about Lyme disease on the Internet, and given that Lyme causes a range of rather common symptoms, patients can end up erroneously thinking they have Lyme, explains Hatchette. (Many other doctors share this concern.)
Private US labs report questionable Lyme disease diagnoses
Current Lyme disease tests are not perfect, but medical experts say they’re the best we’ve got. Advocates for changes in the mainstream diagnosis and treatment of Lyme disease disagree. “Contrary to bureaucratic statements, late stage Lyme disease antibody testing is much less accurate,” the website for advocacy group Can Lyme says. Additionally, some patient advocates including Glazer say the first-line ELISA test is highly inaccurate even in late stages of the disease, and she argues the Immunoblot test should always be performed. “There’s no evidence to back that up,” says Hatchette, who points out that large, well-designed studies trusted by the CDC and Canadian Public Health Laboratory underscore the accuracy of the ELISA test in late Lyme disease.
Not trusting Canada’s testing methods, many Lyme disease advocates encourage Canadian patients to get tested at for-profit labs that specialize in Lyme disease. (The tests can cost around $1,000 per patient.) These labs are allowed to use non-standard methods for testing, due to a regulatory exemption. “They use their own testing criteria that haven’t been peer reviewed,” says Patel.
In a study published in 2014, researchers sent two Lyme specialty labs samples of 40 healthy ‘control’ patients – patients who had no history of Lyme disease and hadn’t been recently exposed to an endemic area. In one of these labs, 11 of the ‘control’ patients tested positive according to the “in-house” interpretation of the Immunoblot IgG test, while only one of the 40 patients tested positive on the CDC version of this test in a university lab. (The test has a false positive rate of about 1%.)
“I’m very worried about people who don’t trust we’re doing our best to provide the current state-of-the-art testing available and instead hang their hat on a result from a private US lab, which in many instances is falsely positive,” says Sider.
The positive results can lead some people to seek doctors who treat them with months or even years of antibiotics – treatment that most in the medical community think is not beneficial and potentially dangerous. Plus, says Hatchette, “If you think you have Lyme disease without great evidence for it, you may be missing something else.”
Glazer finds that argument unfair. “It’s not as if people are getting all these other diagnoses and they’re fixated on Lyme disease.” Glazer says patients who think they have Lyme disease have been told their symptoms are “psychosomatic,” or have been given a diagnosis that doesn’t make sense to them. For example, doctors thought Glazer had fibromyalgia or chronic fatigue syndrome, but those conditions tend not to worsen while Glazer was getting “sicker and sicker.”
Hatchette is sympathetic to patients’ frustrations. “There’s no question that people who think they have Lyme disease are suffering from something and their stories are quite moving,” he says. He thinks other provinces should introduce complex chronic disease clinics like those established at the BC Women’s hospital, which can help researchers learn from patients and more quickly arrive at diagnoses. “We need to do more for these patients,” he says.
What’s being done to improve Lyme disease surveillance and diagnosis
In recent years, Ontario has started to do “more active surveillance” of Lyme disease, says Sider. Public Health Ontario is working to increase public health units’ usage of a standardized questionnaire for patients who have tested positive for Lyme disease. When people in an area not known to be endemic begin developing Lyme disease (in spite of not travelling to an endemic area), public health employees will go to those areas and drag sheets of diaper flannel, a material that ticks latch on to, and then test those ticks. Increasingly, more of these surveys will inform Public Health Ontario’s Lyme risk maps.
Provincial and federal Public Health Agencies are working to raise awareness among doctors regarding Lyme disease symptoms and that Lyme can be found in areas not officially recognized as ‘endemic’. “I think we are better equipped for responding to the growing risk of Lyme disease than we were five years ago,” says Marc Ouelette, scientific director of the Institute of Infection and Immunity at the Canadian Institutes for Health Research. Indeed, part of the increase in Lyme diagnoses could be a result of increased awareness, rather than increased risk, he points out.
Meanwhile, researchers are working to improve tests. Scientists are looking for biomarkers that might be present in early Lyme disease that could be tested for before the development of antibodies, says Patel. He estimates, however, that it would be years before such tests are available. And Ouelette points out that CIHR is funding several projects to better understand Lyme disease.
As we wait for these improvements, the Lyme diagnosis controversies continue. And in reality, both the advocates who think Lyme is underdiagnosed and the experts who think Lyme concerns are overestimated are right, explains Gregson. “If you have symptoms and you’re in an area where Lyme is a possibility but you haven’t been tested, or you’ve been tested too early and not retested, then there’s an issue of Lyme disease being missed,” he says. “But if you’re getting tested for Lyme by a laboratory that uses non-standardized methods, then your biggest risk is getting a false positive.”