From the Guidelines
The Lyme antibody screen result is negative, with a value less than 0.90 index, indicating no serological evidence of Lyme disease infection at this time. This result is based on the 2-tiered serologic analysis, which is the recommended laboratory test in the United States for confirming the diagnosis of Lyme disease 1. The test measures antibodies produced by the immune system in response to Borrelia burgdorferi, the bacterium that causes Lyme disease. A negative result suggests that the patient has not been infected with this bacterium, or the infection is too recent for antibodies to have developed. Some key points to consider when interpreting this result include:
- The sensitivity of the 2-tiered testing is low (30%–40%) during early infection, while the antibody response is developing (window period) 1.
- For disseminated Lyme disease, the sensitivity is 70%–100%, and specificity is high (>95%) during all stages of disease 1.
- If the patient is experiencing symptoms consistent with early Lyme disease (such as rash, fever, fatigue, or joint pain) despite this negative result, follow-up testing might be warranted, as antibodies may take several weeks to develop after infection 1. It is essential to interpret this test result alongside the patient's symptoms and exposure history to determine the best course of action.
From the Research
Interpretation of LYME AB SCREEN Results
The LYME AB SCREEN results are interpreted based on the index value, with the following categories:
- Negative: index value < 0.90
- Equivocal: index value 0.90-1.09
- Positive: index value > 1.09
Treatment of Lyme Disease
According to the studies, the following antibiotics are effective for treating Lyme disease:
- Oral amoxicillin (1.5 g/day) 2
- Oral azithromycin (0.5 g/day) 2
- Injectable ceftriaxone 2, 3
- Injectable cefotaxime 2
- Doxycycline 4, 5
Diagnosis of Lyme Disease
The diagnosis of Lyme disease is based on a two-tier strategy:
- Screening test using an immunoenzymatic technique (ELISA) 4, 6, 5
- Confirmatory test with a Western blot technique for its better specificity 4, 6, 5 The seroconversion occurs after approximately 6 weeks, with IgG detection (sensitivity and specificity both >90%) 4
Pediatric Decision Limits for Serologic Screening of Lyme Disease
The proposed ranges for IgM and IgG are:
- IgM: negative ≤0.20, equivocal ≥0.21 to <0.32, positive ≥0.32 6
- IgG: negative ≤0.50, positive >0.50 6
Key Points
- The efficacy and safety of antibiotics for treating Lyme disease are still controversial 2
- Ceftriaxone and doxycycline can induce seroconversion in previously seronegative patients with clinically suspected disseminated Lyme disease 3
- The treatment of Lyme disease should be based on clinical criteria, and serological follow-up is not recommended 4
- The duration of antimicrobial therapy for babesiosis in severely immunocompromised patients should be extended to 6 weeks or longer 5