Objective: To determine the reason(s) why serologic tests for Lyme disease are performed, who initiates the test requests, and how the test results are used in a clinical setting.
Design: Retrospective cohort.
Setting: Prepaid health plan in northern California.
Patients: Consecutive sample of 117 patients for whom at least one serologic test for Lyme disease was performed during a 3-month period.
Main outcome measures: Reason for ordering and result of the serologic test, differential diagnoses, and treatment.
Results: One of 117 patients had antibodies to Borrelia burgdorferi. Fifty-six percent of test requests were initiated by the physician and 35% by the patient. Of 66 tests ordered by the physician, 20% were performed because of suspected early Lyme disease, 6% as follow-up of a tick bite, 2% to confirm a prior history of Lyme disease, 14% as a workup for arthritis, and 60% as one of a battery of laboratory tests for vague symptoms. Of 41 tests initiated by the patient, 51% were performed because of a history of a tick bite. The reasons for ordering 10 tests were undetermined.
Conclusion: Only 19% of all serologic tests for Lyme disease were performed because the physician suspected Lyme disease in the patient. Particularly in light of the low probability of contracting Lyme disease in California, it appears that this serologic test is being overused. Indiscriminate testing increases health care costs and does not appear to affect treatment decisions. Education is needed regarding the limitations of this serologic test.