Should I test my patient with Reactive arthritis for Lyme disease or other infections?

Testing for Lyme Disease in Patients with Reactive Arthritis

Testing for Lyme disease is not routinely recommended in patients with reactive arthritis unless there is specific clinical or epidemiologic support for Lyme disease diagnosis. 1

Diagnostic Approach for Reactive Arthritis vs. Lyme Arthritis

Understanding the Distinction

• Reactive arthritis is typically triggered by gastrointestinal or genitourinary infections
• Lyme arthritis is specifically caused by Borrelia burgdorferi infection

When to Consider Lyme Disease Testing

Testing for Lyme disease should be considered in patients with arthritis when:

1. Geographic and exposure factors are present:

   • Patient lives in or has traveled to a Lyme-endemic region 1
   • History of tick exposure or tick bite 2
   • Previous erythema migrans rash 2

2. Clinical presentation is consistent with Lyme arthritis:

   • Mono- or oligoarticular arthritis (fewer than 5 joints) 2
   • Predominant knee involvement, followed by ankle, wrist, and elbow 2, 3
   • Symptoms beginning months after potential tick exposure 4

When NOT to Test for Lyme Disease

• In patients with typical reactive arthritis following known gastrointestinal or genitourinary infection
• In patients with no epidemiologic risk factors for Lyme disease 1
• In low-incidence regions without travel history to endemic areas 1

Diagnostic Testing Algorithm

1. Assess pretest probability based on:

   • Geographic exposure (endemic vs. non-endemic region)
   • Clinical presentation (joint pattern, associated symptoms)
   • History of tick exposure or erythema migrans

2. For high pretest probability:

   • Proceed with two-tiered serologic testing (EIA followed by Western immunoblot) 1
   • IgG antibodies are necessary to confirm Lyme arthritis 2
   • Absence of IgG antibodies essentially rules out Lyme arthritis 2

3. For low pretest probability:

   • Consider alternative diagnoses first
   • Testing has poor positive predictive value and may lead to false positives 1

Testing for Other Infections in Reactive Arthritis

• Standard workup for reactive arthritis should include testing for:
  • Gastrointestinal pathogens (Salmonella, Shigella, Campylobacter, Yersinia)
  • Genitourinary pathogens (Chlamydia, gonococcal infection)
  • HLA-B27 status may be helpful in some cases

Common Pitfalls to Avoid

1. Overdiagnosis in non-endemic areas:

   • Positive Lyme serology has poor predictive value in low-incidence regions 1
   • Even clinical signs considered consistent with Lyme disease have poor predictive value in non-endemic regions 1

2. Misinterpreting persistent antibodies:

   • IgG antibodies can persist for years after treated infection 2
   • Positive serology alone doesn't indicate active infection

3. Inadequate testing methodology:

   • Using Western immunoblot without first-tier EIA is not recommended 1
   • PCR testing has limited clinical utility due to low sensitivity and risk of contamination 1

4. Overlooking other causes of reactive arthritis:

   • Antibacterial treatment is generally ineffective for fully developed reactive arthritis not caused by Borrelia 5
   • Early treatment of triggering infections may prevent or improve reactive arthritis 5

Remember that while Lyme arthritis is a common manifestation of late Lyme disease in endemic regions, reactive arthritis has multiple potential infectious triggers that should be considered in the diagnostic workup.