CDC Lyme Disease Case Definition Often Misused

Many physicians mistakenly rely on the CDC Lyme disease case definition when diagnosing patients with Lyme disease. Some clinicians require that patients meet these strict surveillance criteria before making a diagnosis.

However, the CDC Lyme disease case definition was developed as a public health surveillance tool designed to track the number of Lyme disease cases across the country. It was not intended to guide clinical diagnosis or treatment decisions.

Public health surveillance definitions play an important role in tracking disease trends. However, they were never intended to replace clinical judgment when physicians evaluate individual patients presenting with symptoms.

Many physicians mistakenly defer to the CDC’s surveillance definition when evaluating patients. This can lead clinicians to believe that patients must meet the narrow surveillance criteria in order to receive a diagnosis.²

Perea and colleagues surveyed 1,503 family physicians, internists, pediatricians, and nurse practitioners regarding their use of the Lyme disease case definition.

“Which one of the following best describes how you diagnose and treat Lyme disease?”

• More than 60% of clinicians surveyed reported treating patients with Lyme disease.
• Among the 927 clinicians treating Lyme disease patients, 20% reported relying on the CDC surveillance case definition to guide their decisions.
• However, among clinicians who reported relying on the case definition, the authors found that knowledge of the definition itself was limited.

The clinicians who relied on the CDC case definition were also asked:

“Does the case definition include information on diagnosis and management?”

• Only 31 clinicians (16.4%) correctly answered that the surveillance definition does not include guidance on diagnosis or treatment.
• Most respondents incorrectly believed the CDC definition provided clinical guidance.

The authors concluded that misuse of the Lyme disease surveillance case definition in clinical decision-making continues to occur. However, they also noted that interpretation of this finding is complicated because many clinicians who reported using the case definition were unfamiliar with its actual content.

This confusion highlights one of the broader challenges described in Why Lyme Disease Tests the Limits of Medicine, where surveillance definitions, diagnostic criteria, and clinical judgment are sometimes conflated.

Clinical takeaway: Surveillance definitions were created for public health reporting, not for diagnosing individual patients. Physicians evaluating patients with suspected Lyme disease should rely on clinical judgment, patient history, and diagnostic evaluation rather than surveillance criteria alone.

Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

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