Objective

To evaluate the conditions behind the symptoms in patients with suspected Lyme borreliosis (LB) who were referred to an infectious diseases clinic.

Methods

In this retrospective, population-based study, we collected data from the medical records of all patients referred for infectious disease consultations in 2013 due to presumed LB from a population of 1.58 million. The patients were classified according to the certainty of LB on the basis of their symptoms, signs and laboratory results. Data on the outcomes and subsequent alternative diagnoses during the 4-year follow-up period were reviewed from all of the available patient records from public, private and occupational healthcare providers.

Results

A total of 256 patients (16/100 000) were referred as a result of suspicion of LB; 30 (12%) of 256 were classified with definite, 36 (14%) with probable and 65 (25%) with possible LB. LB was unlikely in 121 (47%) patients. A novel diagnosis was discovered in the background symptoms in 73 (29%) of patients. Previously diagnosed comorbidities caused at least some of the symptoms in 48 (19%) patients. Other explanations for symptoms were found in 81 (67%) of 121 of unlikely and 22 (34%) of 65 of possible LB patients. The spectrum of conditions behind the symptoms was quite broad and most often were musculoskeletal, neurological, psychological or functional disorders.

Conclusions

LB was unlikely in half of the patients with presumed LB. In most cases the patients had other conditions that explained their symptoms.