Behind the Evidence

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 - Mary C. Tierney
Mary C. Tierney

Evidence-based medicine has been building strength over the 15 or so years since the methodologies used to determine “best evidence” were largely established by the McMaster University research group led by David Sackett and Gordon Guyatt.

As we know, evidence-based medicine is a way to improve and evaluate patient care. It involves combining the best clinical research evidence, including meta-analyses and systemic reviews of multiple studies, best practice guidelines and a physician’s individual expertise along with the patient’s values to make decisions about medical care.

Examining evidence and building best practices is especially important in health imaging because utilization has surged in recent years, presenting an annual growth rate of 9 percent, nearly one-half more than the annual increase in general medical expenditures (approximately 6 percent). As such, policy-makers and payors are increasingly demanding that evidence-based data justify the utilization of imaging procedures.

Strong evidence is building, serving to differentiate and delineate technology choices for various disease states. For example, a study released in June found PET/CT is the only test necessary in staging or restaging lymphoma patients, as CT alone added no value.

In detecting coronary artery disease, multislice CT and SPECT are “complementary rather than overlapping” technologies, says a 2006 study. The authors said “although a relationship exists between the severity of CAD on multislice CT and myocardial perfusion abnormalities on SPECT, analysis on a regional basis showed only moderate agreement between observed atherosclerosis and abnormal perfusion.”

Cancer patient management is changed for one in three patients due to PET/CT findings, according to National Oncologic PET Registry (NOPR) data released in May. That study also found that PET is associated with a management change in almost 75 percent of patients when the addition or deletion of specific modes of therapy was included. For patients with a pre-PET plan of biopsy, the post-PET plan had a significant impact on care—with biopsies avoided in about 75 percent of the cases analyzed.

In breast imaging, the results of the DMIS Trial are widely known, which found full-field digital mammography (FFDM) superior to film-screen in finding breast lesions in women with dense breasts, who are pre- and peri-menopausal or younger than 50. Less widely known are the recently released stats from the Irish National Breast Screening Program that show FFDM is a superior mammography screening method for all eligible patients. The evidence continues to build better medicine.