A new Lyme disease testing report by investigators from the Centers for Disease Prevention and Control found that 62% of the 3.4 million serologic tests done by large commercial laboratories nationwide in 2008 adhered to the recommended 2-tiered antibody testing approach. However, just12% of the 2.4 million patients tested were infected with Borrelia burgdorferi, the researchers report in an article published online May 30 in Clinical Infectious Diseases.
"We've known that Lyme disease is a very big public health problem," lead author Alison F. Hinckley, PhD, from the CDC's Division of Vector-Borne Diseases, Fort Collins, Colorado, told Medscape Medical News. "With these new data, we now also know that Lyme disease is considered commonly by health practitioners and that most of the testing by these large laboratories is in accordance with diagnostic recommendations." Dr. Hinckley said the number of reported cases in the United States has remained relatively stable since 2008 and that the researchers think the rate of infection has likely remained fairly consistent.
The 12% infection rate raised questions about whether better use of clinical and exposure history might have reduced the $492 million estimated cost for testing. The researchers also note that using 2 enzyme-linked immunoassay tests (also known as EIA or ELISA) might reduce national testing costs by $57 million per year compared with the standard 2-tiered approach.
Dr. Hinckley said, "Before testing a patient for Lyme disease, it is important to consider the likelihood that a patient is infected. If you decide there is a reasonable chance that your patient has Lyme disease, serologic testing may be helpful. Factors to consider are: Symptoms: Does the patient have signs and symptoms consistent with the disease? Geography: Has the patient been in an area where the disease occurs? Behaviors: Does the patient have risk factors for exposure to ticks?"
CDC recommends the 2-tiered approach mainly for patients with signs and symptoms of disseminated disease. The current standard calls for enzyme-linked immunoassay testing followed by Western blots for immunoglobulin G or immunoglobulin M anti–B burgderfori antibodies if the first test is positive or indeterminate. Serologic testing at the time of tick bite in the absence of erythema migrans or other symptoms is not useful because the patient has not yet developed a detectable antibody response.
According to the authors, 2-tiered testing detects less than 40% of early illness (erythema migrans rash, fatigue, chills, fever, headache, muscle and joint aches, and swollen lymph nodes). The 2-tiered test detects 87% of disseminated disease, symptoms of which include additional erythema migrans lesions in other areas of the body, facial or Bell's palsy, severe headaches and neck stiffness resulting from meningitis, pain and swelling in the large joints, shooting pains that may interfere with sleep, heart palpitations, and dizziness.
To estimate the cost of testing and the number of infections among tested patients, the CDC researchers surveyed large commercial laboratories in the United States in 2008 as part of a larger survey of tick-borne diseases. The 7 participating laboratories accounted for more than 76% of Lyme disease tests reported to health departments in Connecticut, Maryland, Minnesota, and New York, the 4 states that are highly endemic for Lyme disease.
The authors report that they also attempted to include laboratories known to provide alternative testing, such as urine or culture testing, but that none of those laboratories agreed to participate.
The participating labs performed about 3.4 million Lyme disease tests on about 2.4 million specimens nationwide. The estimated total direct cost for 2-tiered testing was approximately $336 million. Stand-alone Western blot tests cost $117 million, and stand-alone enzyme-linked immunoassay tests cost $39 million, for a total of $492 million.
The overall estimated percentage of true infections among tested patients from the 4 endemic states was 12%. This estimated rate varied from 10% in Maryland to 18.5% in Minnesota. "Multiplying these percentages by the total number of specimens tested yielded an estimate of 288,000 infected source patients in the U.S., with a range of 240,000 to 444,000," the authors write.
Most of the tests were done using the 2-tiered approach, both overall (62%) and in the 4 Lyme disease–endemic states (68%).
In the 4 endemic states, which would be expected to have the highest incidence of positive tests for Lyme disease, the enzyme-linked immunoassay first-tier tests were positive for 11.89% of patients and confirmed positive for 5.76% of patients using Western blot second tier.
The authors warn that 288,000 is almost certainly an underestimate of the total number of B burgdorferi infections in 2008 because it does not include infections in patients for whom no testing was done, often because they were diagnosed clinically on the basis of the presence of an erythema migrans rash; for whom no test results were available; or who had testing at smaller laboratories, clinics, or hospitals not included in the study.
The authors add, "Serologic testing for the diagnosis of [Lyme disease] has been complicated by inappropriate and excessive use and may be a substantial misuse of healthcare resources. Even when serologic testing is ordered in endemic areas, it may be unwarranted clinically. The low percent positive values reported in this study for tests conducted in four endemic states support this claim."
They conclude, "Given the large number of tests for [Lyme disease] and potential for false results, it is important to consider clinical an exposure history in conjunction with laboratory results for diagnosis and classification of [Lyme disease] for surveillance purposes."
Three coauthors have received funding from the CDC Cooperative Agreement/Connecticut Department of Health contract. Another coauthor has received institutional support through the CDC. Another coauthor has received institutional funding through the CDC Emerging Infections Program Grant, TickNet program. The other authors have disclosed no relevant financial relationships.
Clin Infect Dis. Published online May 30, 2014. Abstract
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Cite this: Many Lyme Tests Unnecessary, Experts Say - Medscape - Jun 06, 2014.