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American College of Physicians Issues Guidelines on Laboratory Evaluation of Lyme Disease

SHARON SCOTT MOREY

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 MEDLINE 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.

General Recommendations

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 nonspecific 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.

American Academy of Pediatrics Releases Report on Cholesterol Levels in Children and Adolescents

SHARON SCOTT MOREY

The Committee on Nutrition of the American Academy of Pediatrics (AAP) has developed a statement on cholesterol levels in children, which is published in the January 1998 issue of Pediatrics. The report reviews the scientific evidence for recommendations of dietary changes in all healthy children and describes the management approach for children who are at increased risk of atherosclerosis in early adult life. The following summarizes the recommended strategies to reduce cholesterol levels in children and adolescents. The strategies include those directed to the population of children at large and those directed specifically to children and adolescents with elevated cholesterol levels.

The AAP statement notes that the aim of the population approach is to lower average blood cholesterol levels in children and adolescents through changes in nutrient intake and eating patterns. According to the AAP statement, no restriction of fat or cholesterol intake is recommended in infants younger than two years of age. By five years of age, though, children should be eating a diet in which saturated fatty acids constitute less than 10 percent of the total calories, total fat intake over several days is no more than 30 percent of the total calories and no less than 20 percent of total calories, and dietary cholesterol is kept at less than 300 mg per day.

Selective Screening of At-Risk Children

Selective cholesterol screening is recommended in children and adolescents with a family history of premature cardiovascular disease or with at least one parent with a high blood cholesterol level. The AAP report specifies that cholesterol screening should be performed under the following circumstances: (1) in children and adolescents whose parents or grandparents, at 55 years of age or younger, underwent diagnostic coronary arteriography and were found to have coronary atherosclerosis (this includes parents and grandparents who have undergone balloon angioplasty or coronary artery bypass surgery); (2) in children and adolescents whose parents or grandparents, at 55 years of age or younger, had myocardial infarction, angina, peripheral vascular disease, cerebrovascular disease or sudden cardiac death; and (3) in children and adolescents with a parent whose total blood cholesterol level is 240 mg per dL (6.20 mmol per L) or higher. If the child's biologic parental history is unavailable, particularly in children with other risk factors, cholesterol levels may be measured to identify children in need of nutritional and medical advice.

Optional cholesterol testing may be appropriate for children who are judged to be at higher risk for coronary heart disease independent of family history. These children might include those who smoke, consume large amounts of saturated fats and cholesterol, have diabetes, have elevated blood pressure or are overweight. AAP also recommends that physicians strongly encourage parents who do not know their cholesterol levels to have them measured.

The AAP report states that the screening protocol varies according to the reason for testing. This variation is suggested to limit the need for more sophisticated analyses. If cholesterol screening is performed because a parent has a total cholesterol level higher than 240 mg per dL (6.20 mmol per L), the initial test should be a total cholesterol measurement. If the child's cholesterol level is higher than 200 mg per dL (5.20 mmol per L), a fasting lipoprotein analysis should be obtained to measure high-density lipoprotein (HDL) cholesterol and low-density lipoprotein (LDL) cholesterol levels. If the child's total cholesterol level is borderline-high (170 to 199 mg per dL [4.40 to 5.15 mmol per L]), a second determination should be obtained and averaged with the first result. If the average is borderline-high or high, a fasting lipoprotein analysis should be obtained.

If cholesterol screening is being performed because of a family history of premature cardiovascular disease, the initial test should be a lipoprotein analysis, which requires a 12-hour fast to obtain an accurate triglyceride level and computation of the LDL cholesterol level. An elevated LDL cholesterol level is considered to be 130 mg per dL (3.40 mmol per L) or higher, and a borderline-high LDL cholesterol level ranges from 110 to 129 mg per dL (2.85 to 3.35 mmol per L). Because of considerable variability among children, the AAP Committee on Nutrition recommends repeating the test so that an average LDL cholesterol level can be calculated.

Management

Management depends on the child's average LDL cholesterol level. For children with acceptable LDL cholesterol levels, the physician should provide education on the recommended dietary guidelines for all healthy children. Lipoprotein analysis should be repeated in five years.

In children with borderline-high LDL cholesterol levels, the physician should provide advice about the risk factors for cardiovascular disease. Step 1 of the American Heart Association diet should be recommended, and other risk factor intervention should be undertaken as appropriate. Lipoprotein analysis should be repeated in one year.

In children with elevated LDL cholesterol levels, an evaluation should be conducted to exclude secondary causes, such as thyroid, liver and renal disorders, and familial disorders. All family members should undergo screening. The Step 1 diet should be followed and, if necessary, the Step 2 diet should be instituted.

The AAP suggests drug therapy only for children 10 years of age or older after six to 12 months of diet therapy has been tried and whose LDL cholesterol level remains 190 mg per dL or higher (4.90 mmol per L or higher) or whose LDL cholesterol level remains 160 mg per dL or higher (4.15 mmol per L or higher) and there is a family history of premature cardiovascular disease (at 55 years of age or under) or two or more other risk factors are present in the child or adolescent after vigorous attempts have been made to control those risk factors. Drugs recommended by the AAP include the bile acid sequestrants cholestyramine and colestipol.

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