How can I tell if I am infected with Borrelia (the cause of Lyme disease)?

How to Know If You Have Borrelia (Lyme Disease)

Start with Clinical Assessment and Exposure History

The diagnosis of Lyme disease is based primarily on clinical findings and exposure history, which takes precedence over laboratory testing, especially in endemic areas. 1

Key Clinical Features to Identify

• Erythema migrans (EM) rash is the hallmark sign, present in 70-80% of cases, appearing as an expanding skin lesion that can range from homogeneous erythema to classic bull's-eye patterns 1, 2, 3
• If you have a physician-documented erythema migrans rash in an endemic area, you can be diagnosed and treated based on clinical signs alone without laboratory confirmation 4, 2
• Accompanying symptoms include fever with sudden onset, chills, headache, myalgia (muscle pain), and arthralgia (joint pain) 1

Critical Exposure History Elements

• Document recent tick exposure and geographic location - patients without recent travel to endemic regions have only a 10% positive predictive value for Lyme serology 1
• Lyme disease occurs primarily in temperate regions of the Northern hemisphere, transmitted by Ixodes ticks 2, 5
• In the northeastern United States, exposure occurs primarily in areas immediately around the home 5

Laboratory Testing Algorithm

Two-Tiered Serologic Testing Approach

Use a stepwise diagnostic approach starting with screening tests, followed by confirmatory testing only if positive or borderline. 6, 1

Step 1: Initial Screening

• Perform IgG-ELISA and IgM-ELISA (or IFA) as screening tests 6, 1
• These tests have high sensitivity but risk cross-reactivity 1

Step 2: Confirmatory Testing

• If screening is positive or borderline, proceed to confirmatory IgG and IgM immunoblot (Western blot) 6, 1
• Do not perform confirmatory testing if screening is negative 6

Interpretation Based on Disease Duration

The timing of your symptoms critically affects test interpretation:

• Early disease (<4 weeks): Both IgM and IgG immunoblot are valid, but sensitivity is only 30-40% because antibodies have not yet developed 1, 4
• If initial testing is negative but symptoms are <4 weeks duration, repeat testing 2-4 weeks after symptom onset to allow for antibody development 4
• Disease >6-8 weeks: Only IgG immunoblot is clinically interpretable; disregard IgM results to avoid false positives 1, 7
• Late disease: Sensitivity increases to 70-100% in disseminated disease 1

Specific Immunoblot Criteria

• IgG positivity requires ≥5/10 specific bands 1
• IgM positivity requires ≥2/3 specific bands 1

Critical Pitfalls to Avoid

The Antibody Window Period Problem

Do not rely solely on serology in early disease - negative serology does not exclude Lyme disease in the first 2-4 weeks because of the antibody window period 1, 4

• Specific antibodies develop approximately 2 weeks after symptom onset 4
• Antibodies reach maximum titers after 3-4 weeks 4
• Early antibiotic treatment can blunt or abrogate the antibody response 4

Persistent Antibodies Are Not Active Infection

Do not misinterpret persistent antibodies as active infection - antibodies persist for months to years after successful treatment and cannot be used as markers of active disease 1, 7

Rule Out Cross-Reactivity

• Perform a T. pallidum hemagglutination assay to exclude cross-reactivity with syphilis, as Borrelia can cross-react with Treponema pallidum 6, 1

Additional Diagnostic Methods for Specific Scenarios

Direct Pathogen Detection (Culture or PCR)

Consider culture or PCR only in specific circumstances:

• Seronegative patients with suggestive clinical presentations (atypical EM, suspected neuroborreliosis without detectable antibodies) 6
• Sensitivity varies by specimen type: skin (EM) 50-70%, CSF (neuroborreliosis) 10-30%, synovial fluid (Lyme arthritis) 50-70% 6
• Should only be attempted by reference laboratories 6

Neuroborreliosis Evaluation

• If CNS symptoms are present, lumbar puncture with CSF analysis is recommended 7
• CSF should show lymphocytic pleocytosis and intrathecal antibody production in true neuroborreliosis 7
• Most cases of neuroborreliosis show intrathecally produced antibodies in CSF 4

Disease Staging Context

Understanding the stage helps guide testing interpretation:

• Stage 1 (Early localized): Erythema migrans, often with negative or low antibody titers 2
• Stage 2 (Early disseminated): Neurological abnormalities, developing antibody response 2
• Stage 3 (Late): Arthritis (North America) or acrodermatitis chronica atrophicans (Europe), high IgG titers 4, 2