In the News

Imaging in heart failure, preventing hypoglycemia, and more.

ACC/ACR release recommendations on imaging in heart failure

Recommendations on the appropriate use of imaging in heart failure patients recently were released by the American College of Radiology and the American College of Cardiology Foundation.

This first joint effort on the subject covered the use of imaging for initial diagnosis and evaluation, decisions about revascularization and device implantation, and long-term follow-up, among other indications. The writing group reviewed available literature, presented common clinical scenarios and came to recommendations on the use of 11 possible tests, including rest and rest/stress tests for echo, radionuclide imaging and cardiac magnetic resonance (CMR) imaging, as well as cardiac CT and invasive cardiac catheterization. Resting electrocardiograms and chest X-rays were not included, since they were considered part of routine care.

For patients being initially evaluated for potential or newly suspected heart failure, the experts recommended echo and CMR and saw no role for stress cardiovascular testing, cardiac CT or invasive angiography. If the only information needed is ejection fraction, radionuclide ventriculography may also be useful. Once heart failure has been diagnosed, the preferred imaging strategies to evaluate for ischemic etiology are stress testing, angiography with CT or invasive cardiac catheterization, the experts said.

To select patients for device therapy (implantable cardioverter-defibrillator/cardiac resynchronization therapy), echo and CMR are useful. Most such patients do not need a stress evaluation or invasive cardiac catheterization, according to the recommendations. If patients have a change in clinical status (including device activation), reevaluation of left ventricular function is appropriate, but routine follow-up of ejection fraction is rarely appropriate. In general, patients with changing or worsening symptoms should be tested similarly to those being initially evaluated. If there are additional concerns of ischemia, stress testing is reasonable. For patients with no change in symptoms, testing is rarely appropriate, the experts concluded.

Heart failure patients vary greatly in presentation, so the recommendations should be used in conjunction with sound clinical judgment, the authors noted. They believe that implementation of the criteria could lead to high-quality and efficient care but also noted that the evidence in this area is rapidly evolving and the document will likely need to be updated. The recommendations were published in the May Journal of the American College of Cardiology.

CT scans ordered for other reasons may detect osteoporosis

Computed tomography scans ordered for other reasons may be an acceptable method of detecting osteoporosis without exposing a patient to additional radiation, according to a recent study.

In a cross-sectional study at one U.S. academic medical center, researchers used computed tomography (CT) scans performed for other clinical indications to compare bone mineral density (BMD) assessment on CT versus dual-energy X-ray absorptiometry (DXA). CT-attenuation values of trabecular bone between the T12 and L5 vertebral levels were measured in Hounsfield units (HU), with emphasis on the L1 measures. BMD was measured by DXA as the reference standard. The study results appeared in the April 16 Annals of Internal Medicine.

A total of 1,867 adults (2,063 CT-DXA pairs) had CT and DXA during a six-month period. Patients with osteoporosis on DXA had significantly lower CT-attenuation values at all vertebral levels (P<0.001). A CT-attenuation threshold of 160 HU or less at the L1 vertebra was found to be 90% sensitive and a threshold of 110 HU was found to be over 90% specific for distinguishing between osteoporosis and osteopenia and normal BMD. At L1 CT-attenuation thresholds less than 100 HU, positive predictive values for osteoporosis were 68% or more, while negative predictive values were above 99% at a threshold above 200 HU. One hundred nineteen patients had at least one moderate to severe vertebral fracture, and of these, 62 (52.1%) had false-negative DXA results while 97% had an L1 or mean T12 to L5 vertebral attenuation of 145 HU or lower.

The authors noted that the potential benefits and costs of the different CT-attenuation thresholds were not assessed and that DXA is itself not a perfect reference standard for osteoporosis. However, they concluded, “abdominal CT images obtained for other reasons that include the lumbar spine can be used to identify patients with osteoporosis or normal BMD without additional radiation exposure or cost.”

The authors of an accompanying editorial said they believed the current results would be best used to rule in patients who are at high risk for fracture because of densitometric or clinical osteoporosis. They noted that this approach may seem conservative but is justified because a significant proportion of CT scans already report incidental findings, many of which are never followed upon. “Systematically adding more information to reports already replete with incidental findings that are not being acted on should be undertaken with trepidation,” the editorialists wrote.

They also said that tolerance for false-positive results should be low and that a threshold yielding 90% specificity, a positive likelihood ratio of 6 and a post-test probability of approximately 70% should be used.

Clinicians may order fewer tests if they know lab fees, study suggests

Giving fee information to clinicians at the time they order lab tests modestly decreased their test ordering, a study found.

Researchers used fiscal year 2007 data from The Johns Hopkins Hospital, which orders about 3.6 million inpatient tests per year. They made lists of the 35 most frequently ordered lab tests and the 35 most expensive lab tests ordered in the hospital.

Each test was then randomly assigned to be an “active” test or a control test. During a six-month baseline period researchers did not display any fee information to providers.

During the six-month intervention period exactly one year later, researchers displayed the fees of only the active tests to ordering clinicians via a computerized provider order entry (CPOE) system. Clinicians weren't told that the fee display was part of a study. Outcomes included the total orders placed, frequency of orders, and charges associated with orders. Results were published online April 15 by JAMA Internal Medicine.

For the active arm tests, test ordering rates fell 8.59%, from 3.72 tests per patient-day during baseline to 3.40 tests per patient-day in the intervention period (P<0.001).

For the control arm tests, ordering rose 5.64%, from 1.15 to 1.22 tests per patient-day (P<0.001). The total charge difference in the active arm was a decrease of $3.79 per patient-day, with a charge increase in control tests of $0.52 per patient-day, leading to a net hospital-wide charge decrease of $436,115 during the intervention period for the combined groups.

There was a substantial decrease in the ordering frequency of comprehensive metabolic panels (active arm) and an increase in frequency for basic metabolic panels (control arm). In total, seven of the diagnostic tests in the active arm and none in the control arm exhibited a total charge decrease of more than $25,000 between the intervention and baseline periods.

The results suggest that displaying test order fees may reduce the number of inappropriately ordered diagnostic tests, and thus save money, the authors wrote. “Although the overall financial impact is modest, our study offers evidence that presenting [clinicians] with associated test fees as they order is a simple and unobtrusive way to alter behavior,” they wrote. “No extra steps were added to the ordering process and no large-scale educational efforts accompanied this exportable intervention.”

An editorialist called the study intervention effective, but also a “blunt instrument” which may have inhibited necessary tests as well as unnecessary tests. “Recent studies suggest that underuse of tests is as much a problem as overuse,” he wrote. Moving forward, researchers should create refined computer-based decision support algorithms that reduce unnecessary test orders while retaining and perhaps increasing the necessary orders, he concluded.

Consensus statement offers strategies for preventing hypoglycemia

Consequences of hypoglycemia and strategies to prevent this condition in patients with diabetes were discussed in a recent consensus statement from the American Diabetes Association (ADA) and The Endocrine Society.

The statement updated a 2005 ADA workgroup report. Experts from both specialty organizations considered data from recent clinical trials and other studies and also used expert opinion to develop their conclusions. The statement was published in Diabetes Care and the Journal of Clinical Endocrinology and Metabolism on April 15.

The consensus statement confirmed previous definitions of hypoglycemia and noted several challenges of accurately measuring blood glucose. For example, the consensus statement discussed the inaccuracies of point-of-care meters in critical care settings, but concluded that continuous glucose monitors are not yet suitable for use in ICUs. Although hypoglycemia occurs more frequently in patients with type 1 diabetes, the greater prevalence of type 2 diabetes means that most episodes occur in type 2 patients, the consensus authors noted. Recent evidence (including the ACCORD, ADVANCE and VADT trials) indicates that hypoglycemia may negatively affect mortality and cognitive function especially in patients with type 2.

Elderly patients are particularly vulnerable to hypoglycemia, the consensus statement noted. Therefore, the experts recommended for these patients careful education and regular reinforcement regarding the symptoms and treatment of hypoglycemia, assessment of functional status to properly apply individualized goals, avoidance of arbitrary short-acting insulin sliding scales and glyburide, simplification of complex regimens, and education about hypoglycemia for caregivers and staff in long-term care facilities.

In general, glycemic targets should be based on a patient's age, life expectancy, comorbidities, preferences and an assessment of how hypoglycemia might impact his or her life, the statement said. For healthy adults with diabetes, a reasonable goal might be the lowest hemoglobin A1c that does not cause severe hypoglycemia, preserves awareness of hypoglycemia and doesn't result in an unacceptable number of hypoglycemic episodes. For patients with long-standing disease and advanced complications or limited life expectancy, the goals may be relaxed.

Strategies to prevent hypoglycemia include patient education (for both the patient and any domestic companions, possibly including interviewing to help identify precipitating factors of hypoglycemic episodes), dietary interventions (such as carrying carbohydrates at all times), exercise management, medication adjustment (substitution of rapid-acting insulin for regular insulin or other oral agents for sulfonylureas), and glucose monitoring.

Clinicians should also assess the risk of hypoglycemia at every visit with patients on insulin or insulin secretagogues (an example questionnaire is provided in the consensus statement) and make a careful review of the patient's glucose log for date, time and circumstances of any hypoglycemia episodes.