Ajax Harwood Clinic

Lyme disease testing: should I be tested?

Last reviewed 2026-09-23Content vef1216ebf782
Reference tool — not medical advice. Clinician judgement always required.

Lyme disease

Defined testing criteria

Also called: Lyme disease, borreliosis, tick bite disease, erythema migrans, bullseye rash

Patients ask about Lyme disease after a known tick bite, after finding a rash, after reading about Ontario's expanding tick risk areas in the news, or after an ND suggests it as an explanation for fatigue, joint pain, or other chronic symptoms. Lyme risk areas now cover much of southern Ontario, so a real exposure history is worth taking seriously. Public Health Ontario's risk map shows the current areas.

Raises suspicion

  • • A known tick bite, or time in a wooded, grassy or brushy area within an Ontario Lyme risk area in the weeks before symptoms started. Risk areas have expanded across southern Ontario; check Public Health Ontario's current risk map, which updates yearly [5]. Locally, Durham Region Health reports that black-legged ticks can be found throughout Durham Region [6]
  • • An expanding red rash, often but not always with central clearing (erythema migrans), starting days to weeks after a tick bite
  • • New facial droop, other neurologic findings, or a new irregular heartbeat, fainting, or chest discomfort several weeks after a tick bite (possible neurologic or cardiac Lyme disease)
  • • A single swollen joint, often the knee, appearing weeks to months after a tick bite, in someone from a Lyme risk area (Lyme arthritis)

Does not raise suspicion

  • • Chronic fatigue, brain fog, or generalized body aches with no known tick bite, no rash, and no time spent in a Lyme risk area
  • • A single positive Lyme test result from a private, non-PHO laboratory used to explain long-standing, multisystem symptoms with no other supporting feature
  • • A tick bite alone with no rash and no other symptom: most tick bites in Ontario do not transmit Lyme disease, and a bite by itself is not a reason to test

Red flags

  • • Facial palsy, other new neurologic deficits, or symptoms of meningitis (severe headache, neck stiffness, light sensitivity)
  • • New palpitations, fainting, or chest pain suggesting Lyme carditis (heart block), which can progress quickly and needs prompt assessment

Who to test

  • A classic expanding erythema migrans rash with a compatible exposureThis is a clinical diagnosis. Treat without waiting for serology; antibody levels are often still negative this early.
  • A compatible exposure and symptoms of disseminated or late Lyme disease (facial palsy or other neurologic findings, carditis, or Lyme arthritis) with no erythema migrans to diagnose clinically: Lyme disease serology (two-tier, via Public Health Ontario) (Situation-specific)Two-tier serology via Public Health Ontario. Facial palsy, carditis or meningitis symptoms need prompt assessment; do not wait for results if red flags are present.

More likely instead

  • • Fatigue, brain fog, or generalized aches with no tick exposure history are far more often explained by chronic-fatigue-syndrome, fibromyalgia, depression, apnea, or another cause of fatigue than by Lyme disease
  • • A single swollen joint can also be from ra, osteoarthritis, gout, or a septic joint, which need their own assessment regardless of tick exposure

Counselling script

“If you have a tick bite followed by an expanding rash, that's Lyme disease and we can treat it now, without waiting on a blood test. If you don't have a rash but you have a real exposure and something like a swollen joint, facial weakness, or heart symptoms, two-tier testing through Public Health Ontario is the right next step. Without an exposure history or one of those specific features, a positive result from a private out-of-province lab isn't something I'd act on.”

Chart snippet (OSCAR-safe plain text)

Concern discussed, not tested

Concern re: Lyme disease discussed.
Discriminating features: tick bite or time in a Lyme risk area, erythema migrans rash, facial palsy or other neurologic findings, carditis, single swollen joint; absent.
Assessment: no exposure history or discriminating feature identified today.
Plan: Lyme serology not ordered; reassurance given.
Ref: PHAC Lyme disease health professionals guidance 2026; IDSA/AAN/ACR Lyme guideline 2020.
Patient given info page: https://lyme.ajaxharwoodclinic.com/patient
Revisit if: tick bite, expanding rash, facial weakness, new irregular heartbeat, or a swollen joint develops.

Testing ordered

Ordered: two-tier Lyme serology via Public Health Ontario. Indication: compatible exposure with symptoms of disseminated or late Lyme disease, no erythema migrans present to diagnose clinically.
Plan: erythema migrans with compatible exposure is treated clinically without serology. Facial palsy, carditis or meningitis features assessed and treated promptly regardless of test turnaround.
Ref: PHO Lyme Disease Serology test information 2026; PHAC Lyme disease health professionals guidance 2026.

Revisit if

  • • New tick bite or expanding rash
  • • Facial weakness, other new neurologic symptoms, or symptoms of meningitis
  • • New palpitations, fainting, or chest discomfort
  • • A new swollen joint, particularly the knee

References

  1. 1. Public Health Agency of Canada. Lyme disease: For health professionals (2026)Early localized Lyme disease with erythema migrans is diagnosed clinically, without serology
  2. 2. Public Health Ontario. Lyme Disease - Serology: Test Information Index (2026)Public Health Ontario performs two-tier Lyme serology using a modified two-tier testing algorithm
  3. 3. Canadian Rheumatology Association (Pediatric Rheumatology) / Choosing Wisely Canada. Recommendations: Pediatric Rheumatology (2025)Lyme serology should not be ordered without an exposure history or residence in a Lyme-endemic area and a characteristic clinical presentation
  4. 4. Infectious Diseases Society of America / American Academy of Neurology / American College of Rheumatology. Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA), American Academy of Neurology (AAN), and American College of Rheumatology (ACR): 2020 Guidelines for the Prevention, Diagnosis and Treatment of Lyme Disease (2020)The 2020 IDSA/AAN/ACR guideline is the current evidence-based clinical practice guideline for diagnosis and treatment of Lyme disease, including neurologic and cardiac presentations
  5. 5. Public Health Ontario. Ontario Vector-Borne Disease Tool (2026)Public Health Ontario's Vector-Borne Disease Tool maps blacklegged tick established risk areas and Lyme disease trends across Ontario (updated yearly)
  6. 6. Region of Durham Health Department. Lyme Disease in Durham Region (2021-2025) infographic (2026)Durham Region Health: black-legged ticks can be found throughout Durham Region
Evidence notes

Tag A: Lyme disease has a defined clinical diagnosis pathway for erythema migrans and validated two-tier serology for disseminated/late disease; not borderline. Durham Region's specific risk-area status was drawn from this session's web search of Public Health Ontario's Vector-Borne Disease Tool and Durham Region public health materials rather than a session-verified quote naming Durham Region by name in a registry source (the registered quote from [5] covers the tool's scope, not the region-by-region risk map itself); the reviewer should confirm current Durham Region risk-area status directly against PHO's interactive map before publication, since it updates annually. Lyme carditis, meningitis and facial palsy are flagged as red flags per [1] and [4] general disease-spectrum knowledge rather than a specific verbatim quote on carditis urgency; this is standard, uncontroversial teaching but worth a direct citation on reviewer pass. Reviewer: removed unverified Durham-specific risk statements from patient and clinician text. A March 2026 Durham Region Health provider update reportedly states that all of Durham Region is now a risk area, but the PDF returned 404 when fetched, so it could not be verified. Before publication (Phase 2), confirm Durham's status on PHO's live Vector-Borne Disease Tool and, if confirmed, restore a sourced local statement, since it matters for Ajax patients. 2026-09-23 (Dr. Yu approved): local Durham line restored, sourced to Durham Region Health's 2021-2025 infographic.

Popular labels: what they mean

"Chronic Lyme disease"

Not a recognized medical diagnosis

Also called: chronic Lyme, chronic Lyme disease, persistent Lyme, Lyme co-infections, Lyme-MSIDS, post-treatment Lyme

Patients hear about 'chronic Lyme disease' from an ND, a support group, or online searches for persistent fatigue, pain, or brain fog, sometimes after a standard Lyme test was negative or was never done. The label is often used loosely to cover very different situations: some patients really did have treated, documented Lyme disease and still have symptoms afterward (a recognized picture called post-treatment Lyme disease syndrome, or PTLDS); others have never had a positive standard test or a plausible exposure at all. Both groups deserve to be taken seriously, and this page treats them separately.

Raises suspicion

  • • This label itself has no discriminating features. A documented history of treated Lyme disease (positive validated testing or a clinically diagnosed erythema migrans, treated with antibiotics) with persistent fatigue, pain, or cognitive symptoms afterward is PTLDS, a real, described picture, not what this page means by 'chronic Lyme'; see the main lyme page for testing and treatment of confirmed Lyme disease.

Does not raise suspicion

  • • Persistent fatigue, joint pain, or brain fog with no tick bite, no exposure to a Lyme risk area, and no positive validated (two-tier) test
  • • A positive result from a private, non-PHO laboratory (IGeneX, Armin Labs, LTT-Lyme, CD57 panel) used on its own to diagnose ongoing infection
  • • Multiple 'co-infections' (babesiosis, bartonellosis, and others) diagnosed by unvalidated private testing to explain the same persistent symptoms

Red flags

  • • None specific to this label. If red flags for active Lyme disease (facial palsy, carditis, meningitis) are present, see the main lyme page.

Who to test

  • Persistent symptoms with no documented history of treated Lyme diseaseInvestigate the persistent symptoms on their own merits (see more_likely_instead), rather than reaching for private-lab Lyme or 'co-infection' testing to keep the Lyme hypothesis open. If a genuine new exposure and compatible presentation exist, use two-tier Lyme serology (see the lyme page).
  • Persistent symptoms after documented, treated Lyme disease (PTLDS)No test confirms or monitors PTLDS. A repeat course of antibiotics has not been shown to help and carries its own risk; investigate and manage the persistent symptoms directly.

More likely instead

  • • ME/CFS
  • • Fibromyalgia
  • • Depression
  • • Post-COVID condition (long COVID)
  • • Sleep apnea
  • • A prolonged but self-limited post-infectious recovery, in someone with a genuine, documented, treated Lyme infection

Counselling script

“If you had a documented, treated Lyme infection and still feel unwell, that's a recognized picture called post-treatment Lyme disease syndrome, and I take it seriously, but a large randomized trial found that extending antibiotics doesn't improve quality of life beyond shorter treatment, so I wouldn't recommend that route. If you don't have a documented Lyme infection, a positive result from a private lab like IGeneX isn't something health authorities consider reliable, and I'd rather look directly at what's causing your symptoms.”

Chart snippet (OSCAR-safe plain text)

Concern discussed, not tested

Concern re: 'chronic Lyme disease' discussed. Patient reports a private-laboratory result or ongoing symptoms attributed to Lyme disease.
Discriminating features: documented history of treated Lyme disease, new exposure with compatible clinical picture; absent or present as noted.
Assessment: unvalidated private-lab testing and 'co-infection' panels do not confirm ongoing infection; if PTLDS, prolonged antibiotics have not shown benefit.
Plan: private-lab Lyme or co-infection testing not ordered or acted on; alternative causes of symptoms discussed.
Ref: CDC caution on unvalidated Lyme testing 2005; Berende et al. PLEASE trial, NEJM 2016.
Patient given info page: https://lyme.ajaxharwoodclinic.com/patient#"Chronic Lyme disease"
Revisit if: red flags for active Lyme disease develop, or symptoms significantly affect daily function despite reassurance.

Revisit if

  • • New tick bite, rash, facial weakness, palpitations, or joint swelling (reassess for active Lyme disease)
  • • Symptoms significantly affecting daily function despite reassurance: reassess for chronic fatigue syndrome, fibromyalgia, depression, sleep apnea, or another treatable cause

References

  1. 1. US Centers for Disease Control and Prevention (MMWR). Notice to Readers: Caution Regarding Testing for Lyme Disease (2005)— older guidelineSome laboratories use Lyme testing methods and interpretive criteria that have not been adequately validated, including lymphocyte transformation tests
  2. 2. New England Journal of Medicine (PLEASE trial). Randomized Trial of Longer-Term Therapy for Symptoms Attributed to Lyme Disease (2016)Randomized trial found longer-term antibiotic treatment gave no additional quality-of-life benefit over shorter-term treatment in patients with persistent symptoms attributed to Lyme disease
  3. 3. Infectious Diseases Society of America / American Academy of Neurology / American College of Rheumatology. Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA), American Academy of Neurology (AAN), and American College of Rheumatology (ACR): 2020 Guidelines for the Prevention, Diagnosis and Treatment of Lyme Disease (2020)Current multidisciplinary evidence-based guideline addressing prevention, diagnosis and treatment of Lyme disease, including persistent symptoms after treatment
Evidence notes

Tag C, not borderline for the 'no documented infection, unvalidated private testing' version of this label, which is the version most often meant by 'chronic Lyme' in ND settings. PTLDS itself (persistent symptoms after a documented, adequately treated Lyme infection) is a genuinely described research entity, not a fabricated one, and this record says so plainly rather than folding it into the same dismissal; the C label here specifically targets the unvalidated-diagnosis and prolonged-antibiotic practice, not the patient's real, ongoing symptoms after real treated Lyme disease. This is the batch's most nuanced tag call and the reviewer should confirm the PTLDS framing reads as respectful rather than dismissive. Host is 'lyme' per the C-label hosting convention (schema.md; consistent with mthfr/adrenal-fatigue precedent).

General clinical reference for Ajax Harwood Clinic. Not medical advice, and not a substitute for individualized clinical assessment.