Healthcare-seeking behaviour preceding diagnosis of Lyme neuroborreliosis: population-based nationwide matched nested case-control study

Objectives: To identify diagnostic opportunities, we investigated healthcare-seeking behaviour among patients with Lyme neuroborreliosis (LNB) within 28 weeks before diagnosis. Methods: We conducted a population-based, nationwide matched nested case-control study (Denmark, 2009–2021). As cases, we included all Danish residents with LNB (positive Borrelia burgdorferi intrathecal antibody index test and cerebrospinal fluid pleocytosis). We randomly selected controls from the general population and matched 10:1 on date of birth and sex. Exposures were assignment of diagnostic codes for symptoms, contact to medical specialties, medical wandering, and undergoing diagnostic procedures. We calculated the weekly and 3-month proportions of individuals with exposures and calculated absolute risk differences with corresponding 95% CI. Results: We included 1056 cases with LNB and 10 560 controls. Within 3 months before diagnosis, the most frequent assigned symptoms were pain (difference: 13.0%, 95% CI: 10.9–15.1). Cases with LNB exhibited increased contact with most specialties, particularly general practitioners (difference: 48.7%, 95% CI: 46.0–51.4), neurology (difference: 14.3%, 95% CI: 11.7–16.8), and internal medicine (difference: 11.1%, 95% CI: 8.7–13.5), and medical wandering (difference: 17.1%, 95% CI: 14.3–20.0). Common diagnostic procedures included imaging of the brain (difference: 10.2, 95% CI: 8.3–12.1), the spine (difference: 8.8%, 85% CI: 7.0–10.6), and the abdomen (difference: 7.2%, 95% CI: 5.4–9.1). The increase in healthcare-seeking behaviour was observed ≤12 weeks preceding diagnosis. Discussion: Pain appears to be an ambiguous symptom of LNB, potentially contributing to delays in establishing the correct diagnosis. It would be difficult to identify patients with LNB more effectively as the increased healthcare-seeking behaviour preceding diagnosis is distributed across many medical specialties.