Evaluating Evidence From A Decision Analysis

Abstract

A 28-year-old man comes to your office with a 6-month history of recurrent attacks of artbritis in his left knee. During each episode the knee is tender, swells slightly, and is mildly red. He denies fevers, chills, gastrointestinal symptoms, or morning stiffness. Each attock lasts about 2 to 3 weeks, then slowly subsides. Last summer, the patient went on a week-long backpacking trip in the mountains. He does not recall seeing a tick on his person or his clothing during the trip, nor did he notice a rash during his outing or after he returned. You find nothing remarkable during his physical examination. You consider Lyme disease in your differential diagnosis, remembering that one of your colleagues treated a patient empirically for Lyme disease early last fall when that patient had a rash that resembled erythema migrans. You are considering testing the patient for Lyme disease but are uncertain about the best approach to take, so a brief review of the literature is in order.

Searching the literature, you come across a decision analysis of test-treatment strategies for patients with suspected Lyme disease.¹ The article describes three common clinical scenarios where Lyme disease is considered in the differential diagnosis: (1) myalgic symptoms, (2) rash resembling erythema migrans, and (3) recurrent oligoarticular inflammatory arthritis. For inflammatory arthritis symptoms (your patient), the article recommends no testing or empirical treatment for Lyme disease. Because this article is a decision analysis and not a report from a high-quality clinical trial, you question whether the findings are valid and should guide your clinical approach to the patient.