From the Guidelines
Lyme disease is considered a clinical diagnosis, and physicians should primarily diagnose it based on symptoms, physical findings, and the possibility of exposure to infected ticks, rather than relying solely on laboratory testing. The clinical approach is crucial in diagnosing Lyme disease, especially in early stages, as laboratory tests may not be positive until several weeks after infection. According to the 2021 clinical practice guidelines by the Infectious Diseases Society of America (IDSA), American Academy of Neurology (AAN), and American College of Rheumatology (ACR) 1, in patients with potential tick exposure in a Lyme disease endemic area who have one or more skin lesions compatible with erythema migrans, clinical diagnosis is recommended rather than laboratory testing.
Some key points to consider in the clinical diagnosis of Lyme disease include:
- The presence of a characteristic erythema migrans rash, which is a gradually expanding annular lesion greater than 5 cm in diameter
- The possibility of exposure to infected ticks, particularly in endemic areas
- The patient's clinical presentation, including symptoms such as fever, lymphadenopathy, myalgias, or arthralgias
- The geographic location and season, as Lyme disease is more common in certain regions and during certain times of the year
Laboratory tests, such as the two-tier testing approach (ELISA followed by Western blot), can be used to support the diagnosis, but should not be the sole basis for diagnosis, especially in early disease 1. Treatment should not be delayed if clinical suspicion is high, and early Lyme disease is typically treated with doxycycline, amoxicillin, or cefuroxime. The clinical approach is crucial because waiting for serological confirmation could delay treatment and lead to more severe manifestations of the disease, including neurological, cardiac, or arthritic complications.
It is also important to note that while laboratory testing is necessary to confirm the diagnosis of extracutaneous manifestations of Lyme disease, clinical findings alone are sufficient for the diagnosis of erythema migrans 1. However, the most recent and highest quality study, the 2021 IDSA guidelines 1, recommends clinical diagnosis over laboratory testing for patients with potential tick exposure and skin lesions compatible with erythema migrans.
From the Research
Clinical Diagnosis of Lyme Disease
- Lyme disease is considered a clinical diagnosis, with diagnosis typically made based on clinical manifestations and serology 2, 3.
- The clinical features of Lyme disease are well-characterized and include early localized infection, early disseminated infection, and late disseminated infection 3, 4.
- The disease is transmitted through the bite of an infected tick and can cause a range of symptoms, including erythema migrans, fever, malaise, fatigue, headache, myalgias, and arthralgias 3.
Diagnostic Challenges
- Diagnosis of Lyme disease can be challenging due to the varied clinical manifestations and the need for a two-step serological approach 4.
- Serologic features can be misinterpreted, and false positives can occur if confirmatory laboratory testing is not performed 2.
- Clinical expression of Lyme disease is in part determined by Borrelial variability, with some strains being more arthritogenic than others 5.
Treatment and Prognosis
- Treatment of Lyme disease typically involves antibiotics, such as doxycycline or amoxicillin, and is usually curative 5, 3.
- Late or severe disease may require intravenous antibiotics, such as ceftriaxone or penicillin G 3.
- With early diagnosis and appropriate treatment, patients with Lyme disease typically have a good prognosis 6.