Utilization of serology for the diagnosis of suspected Lyme borreliosis in Denmark: survey of patients seen in general practice.
BACKGROUND
Serological testing for Lyme borreliosis (LB) is frequently requested by general practitioners for patients with a wide variety of symptoms.


METHODS
A survey was performed in order to characterize test utilization and clinical features of patients investigated for serum antibodies to Borrelia burgdorferi sensu lato. During one calendar year a questionnaire was sent to the general practitioners who had ordered LB serology from patients in three Danish counties (population 1.5 million inhabitants). Testing was done with a commercial ELISA assay with purified flagella antigen from a Danish strain of B. afzelii.


RESULTS
A total of 4,664 patients were tested. The IgM and IgG seropositivity rates were 9.2% and 3.3%, respectively. Questionnaires from 2,643 (57%) patients were available for analysis. Erythema migrans (EM) was suspected in 38% of patients, Lyme arthritis/disseminated disease in 23% and early neuroborreliosis in 13%. Age 0-15 years and suspected EM were significant predictors of IgM seropositivity, whereas suspected acrodermatitis was a predictor of IgG seropositivity. LB was suspected in 646 patients with arthritis, but only 2.3% were IgG seropositive. This is comparable to the level of seropositivity in the background population indicating that Lyme arthritis is a rare entity in Denmark, and the low pretest probability should alert general practitioners to the possibility of false positive LB serology. Significant predictors for treating the patient were a reported tick bite and suspected EM.


CONCLUSIONS
A detailed description of the utilization of serology for Lyme borreliosis with rates of seropositivity according to clinical symptoms is presented. Low rates of seropositivity in certain patient groups indicate a low pretest probability and there is a notable risk of false positive results. 38% of all patients tested were suspected of EM, although this is not a recommended indication due to a low sensitivity of serological testing.
Department of Clinical Microbiology, Næstved Hospital, Region Zealand, Næstved, Denmark. ramd@regionsjaelland.dk
Ram B
RB
Dessau
Jette M
JM
Bangsborg
Tove
T
Ejlertsen
Sigurdur
S
Skarphedinsson
Henrik C
HC
Schønheyder
D000293:Adolescent; D000328:Adult; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D001733:Bites and Stings; D015748:Borrelia burgdorferi Group; D002648:Child; D002675:Child, Preschool; D003718:Denmark / Q000453:epidemiology; D004797:Enzyme-Linked Immunosorbent Assay / Q000706:statistics & numerical data*; D005260:Female; D058006:General Practice; D058005:General Practitioners; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D007223:Infant; D008193:Lyme Disease / Q000175:diagnosis* / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D011795:Surveys and Questionnaires; D013987:Ticks; D055815:Young Adult
D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; D007075:Immunoglobulin M