Am Fam Physician. 1998;57(9):2265-2266
The American College of Physicians (ACP) has developed a guideline for the laboratory evaluation of Lyme disease. The two-part guideline is published in the December 1997 issue of Annals of Internal Medicine. Part 1 is a position paper that summarizes the ACP recommendations for the use of serologic testing in patients with suspected Lyme disease. Part 2 of the guideline is a background paper that provides information on the quantitative and qualitative evaluation of the predictive value of a laboratory diagnosis of Lyme disease. Data from this analysis were used to formulate the recommendations for the laboratory evaluation of Lyme disease. Statements in the three-page position paper (Part 1) are cross-referenced with pertinent sections in the 15-page background paper.
Both documents are available on the ACP Web site (http://www.acponline.org). Part 1 may also be obtained by requesting a copy from the Customer Service Representative, American College of Physicians, Independence Mall West, Sixth Street at Race, Philadelphia, PA 19106-1572.
The background paper was developed through a MED-LINE search of articles on Lyme disease published from 1982 to 1996. Studies eligible for inclusion in the analysis were those that contained a clear statement on the test used, a description of the study that permitted calculation of sensitivity and specificity, data on the presence or absence of criteria for Lyme disease and cases of Lyme disease in which the clinicians were blinded to the results of the diagnostic tests being evaluated. Sensitivity, specificity and likelihood ratios were calculated from the data in the studies reviewed.
In calculations of the sensitivity and specificity of the tests, four categories of endemicity were considered: low (incidence estimate: 0.01 percent), moderate (incidence estimate: 0.1 percent), high (incidence estimate: 1 percent) and very high (incidence estimate: 3 percent). The background paper includes nomograms for the use of enzyme-linked immunosorbent assay (ELISA) in different circumstances depending on the patient's clinical presentation and the endemicity of the disease. Three hypothetical clinical presentations were considered: a patient with nonspecific myalgia, a patient with possible erythema migrans and a patient with recurrent oligoarticular inflammatory arthritis.
The following summarizes the general recommendations in Part 1 of the guideline. The guideline states that laboratory confirmation is not required in patients who present with erythema migrans and are from an area where Lyme disease is endemic. Confirmation of late disease, however, requires objective evidence of a clinical manifestation of disseminated disease and laboratory evidence of infection. The guideline notes that skin culture of erythema migrans lesions may be useful. Published reports indicate that saline-lavage needle aspiration and 2-mm punch biopsies of the leading edge of a suspicious lesion may yield the organisms in 60 to 80 percent of cases.
As stated in the guideline, “a central message . . . is the importance of appreciating the limitations of laboratory tests for Lyme disease.” Limitations are especially a factor when the probability of Lyme disease is low (less than 0.20) on the basis of the incidence of the disease in the community and the lack of objective clinical signs.
The general recommendations state that patients with such symptoms as arthralgia, myalgia, headache, fatigue or palpitations alone, without objective signs, have an extremely low probability of Lyme disease and should not be evaluated with laboratory testing. According to the recommendations, a positive ELISA test result in patients with a low (less than 0.20) probability of Lyme disease is more likely to be a false positive than a true positive. ELISA testing is appropriate, however, when the patient's exposure history and clinical presentation suggest that the probability of late Lyme disease is greater than 0.20. This degree of probability requires the presence of characteristic symptoms and signs of Lyme disease, which, the recommendations state, are almost never present in patients with non-specific diffuse myalgia.
Recommendations for Serologic Testing in Suspected Lyme Disease
The following is a summary of the recommendations for use of serologic testing in patients suspected of having Lyme disease.
The first step should be to determine the probability of Lyme disease based on the clinical findings and the incidence of Lyme disease in the population represented by the patient.
The decision to obtain serologic testing should be based on the patient's probability of Lyme disease and the performance characteristics of the test to be used.
In appropriate patients with objective clinical signs and a probability of Lyme disease of 0.20 to 0.80, ELISA or an immunofluorescence assay should be performed. If this first test yields indeterminate results, Western blot testing should be performed.
In patients who present with myalgia (in whom the probability of Lyme disease is low), treatment of symptoms is recommended. Serologic testing is not recommended, and antibiotic therapy for Lyme disease is also not recommended. If testing is performed, a positive result should not be viewed as an indication for antibiotic therapy. A negative result can be used to guide the decision not to initiate antibiotic therapy.
Empiric antibiotic therapy is recommended in patients who present with a rash that resembles erythema migrans or with arthritis, a history of rash resembling erythema migrans and a previous tick bite. Such patients have a high probability of Lyme disease.
The two-step testing strategy is recommended in patients who present with other objective clinical signs (in whom the probability of Lyme disease is indeterminate).
Laboratories that perform tests for Lyme disease should conform to a quality-control standard and improved proficiency program.
Further serologic testing should be performed with suitable controls to improve the estimates of sensitivity and specificity in different settings.
Recommendations for the laboratory diagnosis of Lyme disease should be reevaluated and changed as new information on testing becomes available.