Lyme Disease: Avoiding Inappropriate Serologic Testing
Excerpted from Family Practice News ( Posted: 08/21/2012)
Dr. DeBiasi conceded Lyme serology is confusing, even for infectious disease physicians. The key message is that it must always be a two-step process: Use an enzyme immunoassay or immunofluorescence assay as a screening test and, if it’s positive or equivocal, send the specimen for a standard IgM/IgG Western immunoblot. Antibodies aren’t detectable in the first few weeks of infection but by week 4 the screening test will pick up nearly all B. burgdorferi–infected individuals, albeit with a 5%-7% false-positive rate.
VAIL, COLO. – Misconceptions abound regarding the appropriate use of diagnostic serologic testing for Lyme disease.
The end result is needless difficulties for patients, families, and their physicians, Dr. Roberta L. DeBiasi asserted at a conference on pediatric infectious diseases.
The first point to understand about serologic testing is that it isn’t even guideline recommended in patients who have early localized Lyme disease in the form of erythema migrans. Erythema migrans is a clinical diagnosis that in and of itself is sufficient to trigger the decision to treat.
“This is a major pitfall we see: A child or adult comes in with a classic rash of erythema migrans and the physician decides to do the serology. It comes back negative because the sensitivity and specificity of serologic testing at that stage is abysmal. So the patient’s Lyme disease goes untreated,” she explained.
Children with untreated early-stage Lyme disease have up to a 50% risk of later developing Lyme arthritis, a 10% risk of Lyme meningitis, and a 5% risk of Lyme chronic carditis, according to Dr. DeBiasi, acting chief of the division of pediatric infectious diseases at Children’s National Medical Center in Washington.