Is PCR Useful for the Clinical Diagnosis of Lyme Disease?

Although polymerase chain reaction (PCR)-based assays are being used more often in clinical settings, in general PCR is not useful for the diagnosis of Lyme disease. Two-tiered serology remains the mainstay of laboratory testing for Lyme disease.

Dr. Christina Nelson, Medical Officer in the Bacterial Diseases Branch of Centers for Disease Control and Prevention (CDC; Atlanta, GA, USA) Division of Vector-Borne Disease, spoke about the appropriate use of polymerase chain reaction assays (PCR) in the clinical diagnosis and management of Lyme disease.

PCR testing has limitations. For example, DNA testing does not distinguish between living and dead organisms, and laboratory contamination with amplified DNA poses a risk for false-positive results.

Borrelia burgdorferi, the spirochete that causes Lyme disease, concentrates in collagen-rich connective tissues. Although spirochetes initially disseminate from the site of an infected tick bite via the blood, the bloodborne phase is relatively brief and the concentration of spirochetes is quite low.

PCR detects Borrelia DNA in the blood of fewer than half of patients in the early acute stage of disease when the erythema migrans rash is present. By the time symptoms of Lyme disease have been present for a month or more, spirochetes can no longer be found in blood. Similarly, PCR testing of cerebral spinal fluid (CSF) specimens is not clinically useful. PCR testing of CSF is positive in only about one third of US patients with early neuroborreliosis, and it is even less sensitive in patients with late neurologic disease. Urine is not a suitable sample for PCR testing at any stage of Lyme disease.

Borrelia burgdorferi can be detected by PCR in biopsy samples of infected skin, synovial tissue, or synovial fluid. These tissues are sometimes tested as part of a research study or to assess treatment response in a patient with previously confirmed Lyme arthritis.

However, skin biopsy is not generally recommended because patients with erythema migrans can be reasonably diagnosed and treated on the basis of history and clinical signs alone. The utility of testing synovial fluid is not well established and should be considered only under special circumstances.

Related Links:
Centers for Disease Control and Prevention