Laboratory Bulletin...

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1 Laboratory Bulletin... Updates and Information from Rex Healthcare and Rex Outreach August 1997 Issue Number 23 Pathology Chairman & Administrative Lab Director Robert E. Kanich, M.D. stepped down as Chairman of the Pathology Department in July after having served in that position since Stephen V. Chiavetta, M.D. has been selected as the new Chairman. The new Administrative Laboratory Director, Mrs. Sharon Logue will arrive on August 25. She is a graduate of the University of Maryland with a major in medical technology. While working as an administrative laboratory director, she received an MBA degree from Loyola College in She has extensive laboratory management experience. Stephen V. Chiavetta, M.D. DVT and the new D-dimer Assay Introduction: The D-dimer is a fibrin split product that can be used to evaluate patients with disseminated intravascular coagulation (DIC), venous thrombosis and pulmonary embolus. The D-dimer is a crossed-linked fibrin fragment that is a result of fibrinolysis of a clot. The current D-dimer assay in use at Rex is not sensitive enough to reliably rule out deep vein thrombosis (DVT) or pulmonary embolus. The new SimpliRED D-dimer assay is proven to be more sensitive in detecting DVT and pulmonary embolus. New Test: The SimpliRED assay will replace the current less sensitive method. The clinical usefulness of the D-dimer test is in its negative predictive value, i.e. if the test is negative it is almost certain that there is no DVT. This test should facilitate more rapid triage of patients with clinical suspicion of DVT and pulmonary emboli and avoid unnecessary testing (i.e. venous duplex ultrasonography, lung scans, etc.). Positive results are seen in thrombotic or embolic disorders as well as other fibrinolytic states such as in DIC, post surgery, cancer and postpartum patients. The new test has been evaluated extensively in the literature. A separate study at Rex done in conjunction with the Vascular Laboratory has proven its reliability. Results: The results of the test are reported as positive or negative. The test may be ordered STAT 24 hours a day, seven day a week. The stat turn-around-time after the sample is in the laboratory is 30 minutes. If fibrin split products (FSP) are ordered, the SimpliRED D-dimer assay will be run. The current FSP assay

2 will be discontinued. The charge for the test is $42.00 when run routine. Testing will begin Monday, August 11. Stephen V. Chiavetta, M.D. S. Wayne Smith, M.D. Changes in fibrinogen testing Effective August 18, 1997, at 10:00 a.m., the fibrinogen method and expected values will change. The new assay is based on the Clauss method, which measures the rate of (clottable) fibrinogen to fibrin conversion in the presence of excess thrombin. This method has been shown to be more consistent over time than the current method. There will be a slight change in the fibrinogen reference range. (The reference range was determined by a study of Rex Blood Plan donors and Same Day Surgery patients.) The change is summarized below. Reference Range Old New Fibrinogen mg/dl mg/dl Robert B. Brainard, Ph.D. Elaine Patterson, MT Diagnosing Lyme Disease using serology Recently the FDA issued a Public Health Advisory (July 7, 1997) concerning the diagnosis of Lyme Disease. A positive serology test for antibodies to B. burgdorferi does not necessarily indicate current infection, and patients with active disease may have a negative test result. Serology for Lyme Disease should only be used to support a clinical diagnosis of Lyme disease. The FDA recommends a two step testing process for Lyme Disease serology. The first step is to perform an assay that detects either total or class specific (IgM, IgG) antibodies by using an enzyme-linked immunosorbent technology or indirect immunofluorescence. IgM levels usually peak 3-6 weeks after infection. IgG antibodies begin to be detectable several weeks after infection. The IgG response may continue to develop over the course of several months and generally persists for years. The second step in the testing algorithm employs an assay that is more specific such as the Western Blot. Rex Healthcare Laboratory uses the Vidas immunodiagnostic assay for the first step. This is a very sensitive enzyme-linked fluorescent assay capable of detecting either IgG or IgM antibodies. Sera from positive tests are then automatically referred to the Mayo Reference Laboratory for a Western Blot assay. A negative initial screening assay at Rex indicates that there was not serologic evidence of infection at the time the specimen was collected. A negative result should not be the basis for excluding the diagnosis, especially if blood was collected within 2 weeks of when symptoms began. If Lyme disease is strongly suspected, a second specimen should be collected 2 to 4 weeks after the first specimen and tested. A positive screening test is presumptive evidence of the presence of antibody, but

3 should always be followed with the second step, Western Blot testing. A negative Western Blot test indicates that no reliable serologic evidence of infection was present at the time the specimen was collected. If a strong clinical suspicion of Lyme Disease remains, a second specimen should be collected 2 to 4 weeks after the first specimen and tested. A positive confirmatory Western Blot result provides serologic evidence of past or current infection. A positive result can support, but not establish a clinical diagnosis. Karl T. Kleeman, Ph.D. Moby Lab: Trolling for Disease on the Sea of Managed Care Call me John. Physicians, patients and payors setting sail for the land of Healthtopia (motto: Community Healthcare at Popular Prices ) are hereby advised of two recent articles 1,2 which will be of assistance in compassing their destination. The reports discuss the utility (or lack thereof) of laboratory testing for identifying disease in asymptomatic adults ( case-finding ). Though the methods of study differ, the conclusions reached are remarkably similar. Boland et al prospectively studied ambulatory well patients (mean age 63 +/- 14 years; 57% female) scheduled for a comprehensive general medical evaluation by means of questionnaires to determine patient expectations regarding laboratory testing, physician rationale for laboratory test ordering (evaluate specific diagnosis vs. follow up of known condition vs. case finding), and results or outcomes following laboratory test completion. 1 Five groups of laboratory tests were studied: CBC (no Diff!!!), general chemistry panel ( M12 type - M7, Ca +2, PO 4, uric acid, Alk Phos, & AST), lipid profile (cholesterol, HDL-C, & triglyceride), urinalysis, and thyroid test (either sensitive TSH or T4). All blood specimens were collected when the patient was in the fasting state. After exclusion criteria were applied, the study population comprised 531 patients who had 1,508 tests (7,008 individual components). Of the 1,508 tests, 544 (36%) were abnormal, 33 (6%) were repeated, and 47 (9%) led to further evaluation (additional tests or consults). As a result, there were 73 new diagnoses (4.8% diagnostic yield) and 60 new treatments (4.0% therapeutic yield). Broken down by test category, the highest therapeutic yield was for the lipid panel (16.5%), followed in distant descending order by the chemistry panel (2.8%, predominantly abnormal glucose), CBC (0.9%), urinalysis (0.8%), and thyroid tests (0.7%). There was no association between therapeutic yield and patient age or sex, but the yield was nearly twice as high for new patients (cf. established patients). The authors concluded that their study supports the recommendations of the US Preventive Services Task Force regarding the utility of lipid assessment for case finding in the ambulatory setting, but that general chemistry panels, CBC s, urinalysis, and thyroid testing should not be used routinely for this purpose. In a more general sense, the authors discussed the role of focused testing for conditions with a higher therapeutic yield than current popular testing strategies provide. The College of American Pathologists (CAP) appointed a Laboratory Testing Strategy Task Force which recently published their report on laboratory panel testing for screening and case finding in asymptomatic adults. The task force reviewed published studies on the subject and graded them on the amount of objective outcome data presented. Most reports represented consensus statements

4 and there was little in the way of explicit outcome data which included information on the benefits and costs of testing. The task force then created its own draft practice parameter document, based upon its investigation, and submitted it for review by selected members of the CAP, other medical specialty societies, health insurance companies, and health care delivery systems. The final report was published recently and an abridged summary follows. 2 General recommendations regarding laboratory testing for screening and case finding were: 1. Disease to be detected should be asymptomatic in preclinical stage but detectable inexpensively by appropriate laboratory test. 2. Early medical intervention can prevent or ameliorate the disease. 3. Disease to be detected should be prevalent in the population to be tested, and responsible for a large financial burden to that population. 4. Detection and treatment of the disease provides a net benefit to both the patient and society. 5. Patients with risk factors for disease may require more frequent testing. 6. The role of negative laboratory tests in reassuring patients (particularly those with risk factors) should be considered. 7. Patient s rights as a consumer should be respected. More specific recommendations follow in the accompanying table. John D. Benson, M.D. References: 1. Boland BJ, Wollan PC, & Silverstein MD. Yield of Laboratory Tests for Case-Finding in the Ambulatory General Medical Examination. Am J Med 101: , Glenn GC & Laboratory Testing Strategy Task Force of the College of American Pathologists. Practice Parameter on Laboratory Panel Testing for Screening and Case Finding in Asymptomatic Adults. Arch Pathol Lab Med 120: , For further information, call the Laboratory ( ). Telephone extensions are: Pathologists Direct Line (3201), Robin Ivosic (Core Lab Manager 3053), Linda Lompa (Blood Services Manager ), Kimberly Skelding (Customer Services Manager 3318), Rex Outreach ( ), Karen Sanderson (Lab Compliance Specialist 3396).

5 SUMMARY OF RECOMMENDATIONS FOR SCREENING AND CASE FINDING IN ASYMPTOMATIC ADULTS* College of American Pathologists Laboratory Testing Strategy Task Force 2 Atherosclerotic diseases and cholesterol (screening) Serum cholesterol and HDL-cholesterol measured every 5 years on all adults 20 years of age and older. Fasting specimen not required. Abnormal results should lead to testing for dyslipidemia secondary to hypothyroidism (TSH), diabetes mellitus (glucose) and renal disease (BUN, creatinine). The original sample may be used for this to minimize patient inconvenience. Alternatively a fasting sample may be used. If there is clinical suspicion of renal disease, a creatinine clearance and complete urinalysis may be desirable. If secondary dyslipidemia is not identified by above testing, definitive lipoprotein analysis (lipid panel) is recommended. Thyroid disease (case finding) Test females age 50 years of age or older if they seek medical care. Test all geriatric unit patients on admission and at least every 5 years thereafter. Test any adult aged 50 years or older who visits a medical facility complaining of having other than minor transitory ailments at least every 5 years. Test all adults with newly discovered dyslipidemia for thyroid disease to rule out secondary dyslipidemia. Test for thyroid dysfunction using a sensitive TSH as the initial, front-line analytic procedure. 1. If the TSH measurement is normal, the patient is euthyroid and further thyroid testing is unnecessary. 2. If the TSH measurement is undetectable (<0.1 IU/L), suspect primary hyperthyroidism. Confirm the diagnosis by detecting an elevation of free T 4 (FT4) or perhaps a total T 4 (TT 4 ), total T 3 (TT 3 ), or the FT 4 index, although these latter three tests are less optimal. 3. If the TSH measurement is subnormal but detectable, suspect borderline or fluctuating hyperthyroidism, which may be confirmed as in situation 2 (above). If these measurements fail to confirm hyperthyroidism, recommend repeat testing at a later date and/or consider recommending an endocrinologic work up, which could include a radionuclide scan of the thyroid and a thyrotropin-releasing hormone stimulation test. 4. If the TSH and FT 4 (or TT 4 ) measurements are low, suspect secondary hypothyroidism. Refer for endocrinologic work up. 5. If the TSH measurement is slightly elevated, suspect subclinical or fluctuating hypothyroidism. The diagnosis is confirmed if the FT 4 (or TT 4 ) measurement is low. 6. If a patient has a significant non-thyroidal illness and the TSH measurement is undetectable, hyperthyroidism is probable, but an elevated FT 4 is a more reliable test in this situation. 7. If a patient has a significant non-thyroidal illness and the TSH measurement is elevated and the FT 4 is low, primary hypothyroidism is indicated. In seriously ill patients, thyroid function test results may be altered by the major disease or pituitary function that is suppressed by glucocorticoids, dopamine, or other medications. In general, these patients are not candidates for application of this parameter, which addresses asymptomatic disease. Hemochromatosis and serum iron measurements (screening) Measure iron and iron binding capacity in all adults using a random sample of serum. If the % saturation exceeds 60%, retest using a serum sample following an overnight fast. If the repeat % saturation exceeds 60%, a serum ferritin measurement is indicated. If serum ferritin exceeds 400 ng/ml (400 μg/l) in men or postmenopausal women, or 200 ng/ml (200 μg/l) in premenopausal women, further evaluation is indicated. If serum % iron saturation and ferritin are both below these decision levels on two occasions, the likelihood of hereditary hemochromatosis is very low. Gestational diabetes mellitus, diabetes mellitus, and glucose testing (case finding) Case finding for diabetes mellitus is advised every 3 years or more often in adults aged 40 years or older if there is a history of the disease in a firstdegree relative; in patients with obesity greater than 20% over ideal body weight; in American Indians, Hispanics, or African-Americans with any of the cited risk factors; in patients with previously diagnosed glucose intolerance, unless related to prescription drug use; in patients with hypertension; in women with a history of newborn macrosomia or proven dyslipidemia; and if significant hypercholesterolemia or hypertriglyceridemia are present. If abnormal results are found, consider a glucose tolerance test and a glycohemoglobin test. Test all pregnant females for gestational diabetes, preferably between 24 and 28 weeks gestation, using a 50-g oral glucose load and measuring whole blood, plasma, or serum glucose 1 hour later. Testing requires no preparation and is given without regard to time of last meal. If the 1-hour glucose measurement exceeds 140 mg/dl (7.77 mmol/l), consider retesting the patient using the traditional 100-g oral glucose tolerance test and measure whole blood, plasma, and serum glucose at 1, 2, and 3 hours. Cervical carcinoma and cervical cytology (screening) All sexually active women and any woman 18 years of age or older should have an annual, adequate cervical smear. Postmenopausal women should be examined according to the same program. Follow-up studies are recommended for any degree of abnormality in squamous or glandular cells of undetermined significance. Colorectal cancer and stool examination for occult blood (screening) Perform an annual fecal occult blood test on subjects 50 years of age or older making two smears from separate locations on each of three consecutive stools. Use a guaiac method and hydrate each fecal smear with one drop of deionized water. Patients must abstain from ingestion of red meat, fish, aspirin, vitamin C, and selected fruits and vegetables as suggested by the manufacturer of the test before and during the specimen collection. Selective annual testing is advised for individuals 40 years of age and older who have a personal history of ulcerative colitis, Gardner s syndrome, familial colonic polyposis or history of polyps, prior colon cancer, or a family history of recto-colonic cancer. Prostatic cancer and prostate-specific antigen testing (case finding) Measurements of serum prostate-specific antigen testing should be obtained only if digital rectal examination is performed for the purpose of detecting prostatic cancer. Prostate-specific antigen testing is not recommended as a screening or case finding test on a stand-alone basis. * Modified by J D Benson, MD