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Health Technology Assessment

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AHCPR releases two new health technology assessments

AHCPR's Center for Health Care Technology recently published two Health Technology Assessments. These reports, which are now available from AHCPR, are usually prepared to assist federally financed health care programs, such as Medicare and CHAMPUS (Civilian Health and Medical Program of the Uniformed Services), with coverage decisions. Health Technology Assessments present detailed analyses of the risks, clinical effectiveness, and uses of medical technologies.

Graham, A.A. (1996). Plethysmography: Safety, Effectiveness, and Clinical Utility in Diagnosing Vascular Disease, Health Technology Assessment No. 7 (AHCPR Publication No. 96-0003).

Plethysmography, a semiquantitative method of measuring segmental blood flow and velocity in the carotid and peripheral vascular systems, is safe, easy to perform, and inexpensive. Impedance, strain gauge, air, and photoelectric plethysmographic methods are assessed in this report for their relative safety, efficacy, and clinical utility in diagnosing vascular disease. Clinical evidence has demonstrated, for example, that oculoplethysmography is not a reliable screening test for carotid artery disease, particularly in bilateral disease and nonocclusive unilateral disease. Thus, oculoplethysmography is no longer recommended for the diagnosis of carotid artery disease.

Impedance, strain gauge, and photoplethysmography methods can be used for the initial evaluation of acute and chronic venous insufficiency, although there is great variability in the reliability of these tests to predict venous disease in the presence of nonobstructive thrombi and comorbid conditions. Strain gauge and photoelectric plethysmography can be used safely for the evaluation of peripheral arterial disease, but surgical candidates for arterial reconstruction and some venous disorders may require additional imaging such as duplex ultrasound, venography, or arteriography for anatomic information that is not elucidated by plethysmography. Evaluation of the ability of the plethysmographic techniques reviewed in this report to predict the presence of flow reduction in the carotid and peripheral circulations was based on the technical performance of the tests as compared with a reference method. Establishing evidence-based conclusions proved to be difficult in light of biases such as nonrandomization, unstated patient selection criteria, poor followup of patients, and lack of blindness in some studies.

Erlichman, M. and Holohan, T.V. (1996). Bone Densitometry: Patients with End-Stage Renal Disease, Health Technology Assessment No. 8 (AHCPR Publication No. 96-0040).

The loss of bone mass and osteoporosis are associated with various conditions, such as end-stage renal disease (ESRD), and treatments, such as prolonged steroid therapy. Bone densitometry is used to measure bone mass density, determine the degree of osteoporosis, and estimate fracture risk. Bone densitometers measure the radiation absorption by the skeleton to determine bone mass of the peripheral, axial, and total skeleton. Common techniques include single-photon absorptiometry (SPA) of the forearm and heel, dual-photon absorptiometry and dual-energy x-ray absorptiometry of the spine and hip, quantitative computed tomography of the spine or forearm, and radiographic absorptiometry of the hand. Part I of this report addresses important technical considerations of bone densitometers, including radiation dose, site selection, accuracy, and precision, as well as cost and charges. Part II evaluates the clinical utility of bone densitometry in the management of patients with ESRD. End-stage renal disease affected more than 242,000 Americans in 1992, and each year 10,000 to 20,000 new cases are diagnosed. Although the survival rate of ESRD patients has improved, metabolic bone diseases that fall under the generic term "renal osteodystrophy" represent abnormal development of bone and major long-term complications. Issues addressed in this assessment are the type and extent of bone loss associated with ESRD and whether these patients have an increased risk for fracture.

Value of bone densitometry to improve the outcomes of patients with bone loss remains unproven

About 1.3 million fractures that occur each year in the United States in people over age 45 are attributed to osteoporosis. Bone densitometry is used to measure bone mass density to determine a person's degree of osteoporosis and fracture risk. Whether use of bone densitometry effectively alters the medical management of patients at risk for bone loss remains controversial. Debate continues over selection of the best technique and measurement site, as well as the availability of effective treatments to prevent progression of osteoporosis, if significant bone loss is detected.

Some concern also remains about the accuracy and precision of these techniques, explain Martin Erlichman, M.S., and Thomas Holohan, M.D., of the Center for Health Care Technology, Agency for Health Care Policy and Research. In a recent book chapter, they describe and compare bone densitometry techniques, discuss issues surrounding measurement site selection and accuracy and precision of the techniques, and summarize alternative bone mass measurement techniques such as ultrasound and biochemical markers of bone turnover.

In addition, the authors address conditions for which bone densitometry has been used in clinical practice, such as asymptomatic primary hyperparathyroidism, long-term steroid therapy, and estrogen deficiency. Although patients with these conditions are at increased risk for bone loss, it is not yet clear whether use of bone densitometry to measure bone loss ultimately improves their outcomes. More data from randomized, controlled clinical trials are needed before this conclusion can be reached, according to the authors.

For more information, see "Bone densitometry," by Mr. Erlichman and Dr. Holohan, in Nuclear Medicine: Diagnosis and Therapy, edited by John C. Harbert, William C. Eckelman, and Ronald D. Neumann; New York: Thieme Medical Publishers, Inc., 1996, pp. 865-880.

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