What tests should be ordered to diagnose Lyme and anaplasmosis serology?

Laboratory Testing Orders for Lyme Disease and Anaplasmosis

Lyme Disease Testing Orders

For patients with suspected Lyme disease, order a two-tiered serologic testing approach: start with an enzyme immunoassay (EIA) or immunofluorescence assay (IFA), with reflex Western immunoblot (both IgM and IgG) only if the first test is positive or equivocal. 1, 2, 3

Specific Order Entry Language

• First-tier test: Order "Lyme disease antibody screen by EIA" or "Lyme disease antibody by IFA" 1, 2
• Reflex testing: Specify "reflex to Western immunoblot (IgM and IgG) if positive or equivocal" 1, 2, 3
• Do NOT order Western blot as a standalone test—this dramatically increases false-positive rates and violates standard diagnostic protocols 2, 4

Critical Testing Considerations by Clinical Presentation

• For erythema migrans in endemic areas: Do not order serologic testing—diagnose clinically and treat empirically, as only 30-40% will be seropositive during early infection 2, 5
• For disseminated disease (meningitis, cranial neuropathies, carditis, arthritis): Order the two-tiered testing, which has 88-100% sensitivity for these manifestations 2, 5
• For disease duration <6-8 weeks: IgM Western blot interpretation is valid; for longer duration, only IgG Western blot is clinically interpretable 1

Western Blot Interpretation Criteria

• IgG positivity: Requires ≥5 of 10 specific bands present 1
• IgM positivity: Requires ≥2 of 3 specific bands present (plus positive/equivocal EIA) 1
• These CDC criteria have 96% specificity compared to only 65% specificity for alternative single-tier approaches 4

Anaplasmosis Testing Orders

For suspected anaplasmosis (human granulocytic anaplasmosis), order serologic testing for Anaplasma phagocytophilum antibodies (IgM and IgG) by immunofluorescence assay or immunoblot. 1, 6

Specific Order Entry Language

• Order "Anaplasma phagocytophilum antibody panel (IgM and IgG)" 6
• Consider adding "peripheral blood smear for morulae" as an adjunct test, though negative smears do not exclude the diagnosis 1

Co-infection Considerations

• Co-infection with Lyme disease and anaplasmosis occurs in approximately 8% of cases, as both are transmitted by Ixodes ticks 6
• When clinical suspicion exists for both (fever, headache, myalgia in tick-endemic area), order both Lyme two-tiered testing AND anaplasmosis serology simultaneously 6

Critical Pitfalls to Avoid

• Never order urine antigen tests or CD57 tests for Lyme disease—these lack validation and are not recommended by any guideline 2
• Never retest after treatment—antibodies persist for months to years after successful treatment and do not indicate active infection 2, 3
• Never order testing in low-pretest-probability patients—in non-endemic areas without tick exposure, positive predictive value drops to only 10%, and only 0.7% of patients with arthritis/neuropathy actually have Lyme disease 2
• Geographic exposure is paramount—even highly specific tests produce false-positives when pretest probability is low 2