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Evidence-Based Medicine

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AHRQ releases three new evidence reports

Three new evidence reports were released recently by the Agency for Healthcare Research and Quality. They represent the results of systematic reviews of the evidence on management of acute exacerbations of chronic obstructive pulmonary disease, prevention of venous thromboembolism after injury, and use of dietary garlic. The reports were prepared by Evidence-based Practice Centers (EPCs) supported by the Agency for Healthcare Research and Quality. They provide organizations with comprehensive, science-based information on common, costly medical conditions and new health care technologies.

There are 12 AHRQ-supported EPCs; they systematically review the relevant scientific literature on topics assigned to them by AHRQ and conduct additional analyses when appropriate prior to developing their reports and assessments. The goal is to inform health plans, providers, purchasers, and the health care system as a whole by providing essential information to improve health care quality. Print copies of the report summaries are now available from the AHRQ Publications Clearinghouse. Copies of the full evidence reports will be available in the near future.

Management of Acute Exacerbations of Chronic Obstructive Pulmonary Disease

The Duke University Evidence-based Practice Center (Contract no. 290-97-0014) assessed the evidence currently available concerning the diagnosis, prognosis, and management of acute exacerbations of chronic obstructive pulmonary disease (COPD). COPD, which affects 16 million people and leads to nearly 300,000 hospitalizations annually, is the fourth leading cause of death in the United States. Acute exacerbations of COPD—worsening symptoms of dyspnea and an increase in the amount or purulence of sputum, which may be accompanied by chest discomfort, fever, and other symptoms—are associated with increased short-term mortality when compared with stable COPD.

This report discusses the evidence on clinical assessment of acute exacerbations of COPD (differential diagnosis, prediction of outcome, and level-of-care needs), the effectiveness of various treatments, and the use of noninvasive positive-pressure ventilation in patients with acute exacerbations who have developed respiratory failure. The EPC also provides recommendations for future research.

Select to access the summary online. Print copies of the report summary (AHRQ Publication No. 00-E020) are available from the AHRQ Publications Clearinghouse. Copies of the full report (AHRQ Publication No. 01-E003) will be available from AHRQ in winter 2000.

Prevention of Venous Thromboembolism After Injury

Venous thromboembolism (VT) is an injury-related blood-clotting problem that results in 50,000 deaths and 300,000 to 600,000 hospitalizations annually in the United States. Methods for preventing VT include sequential compression devices, low-dose heparin, low-molecular-weight heparin, vena caval filters, and combinations of these. All of these methods are associated with contraindications and morbidity, which complicates selection of the appropriate method for each patient. This, in turn, leads to wide variability among physicians and prevents consistency in quality of care.

The Southern California Evidence-based Practice Center/RAND (AHRQ contract 290-97-0001) developed this evidence report on prevention of VT after trauma. Their goals were to identify the best method to prevent VT, determine which group of trauma patients is at high risk for developing VT, identify the best method of screening for the problem, and assess the role of vena caval filters in preventing one form of VT (pulmonary embolism) after injury. The report presents their findings and results of meta analyses, identifies gaps in the research literature, and provides recommendations for future research.

Select to access the summary online. Print copies of the report summary (AHRQ Publication No. 00-E026) are available from the AHRQ Publications Clearinghouse. Copies of the full report (AHRQ Publication No. 01-E004) will be available from AHRQ in winter 2000.

Garlic: Effects on Cardiovascular Risks and Disease, Protective Effects Against Cancer, and Clinical Adverse Effects

Dietary use of garlic may lower some types of cholesterol in the short term, but it does not appear to offer long-term protection against cardiovascular disease, according to this evidence report. Garlic may help to reduce low-density lipids (LDL), or "bad" cholesterol and triglycerides, but the evidence suggests only short-term (1 to 3 months) effects. Long-term benefits, if any, have not been determined. The levels of high-density lipids (HDL), or "good" cholesterol, were unaffected. After 6 months, no further reductions in either triglycerides or LDL were apparent. The report calls for additional research to examine the short-term versus long-term benefits of garlic consumption.

The report, which was based on a systematic review and analysis of scientific evidence related to clinical studies of garlic in humans, was prepared for AHRQ by the Evidence-based Practice Center at the University of Texas Health Science Center at San Antonio and the Veterans Evidence-based Research, Dissemination, and Implementation Center (VERDICT), a Veterans Affairs Health Services Research and Development Center of Excellence.

The authors found no evidence that garlic has a beneficial impact on blood pressure or diabetes, and evidence was inconclusive about garlic's role in protecting against cancer. Dietary garlic may possibly be associated with a decreased likelihood of some types of cancer, but the number of available studies was not sufficient to draw conclusions. Also, there is not enough evidence on the different garlic preparations, such as raw, cooked, or supplement form.

Select to access the summary online. Print copies of the report summary (AHRQ Publication No. 00-E022) are available from the AHRQ Publications Clearinghouse. Copies of the full report (AHRQ Publication No. 01-E023) will be available from AHRQ in winter 2000.

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