Medical imaging for managed care plan doubles in 10 years

November 12, 2008

A Seattle nonprofit managed care plan has experienced the same rapid growth in high-tech medical imaging utilization as federal health insurance programs.

A Seattle nonprofit managed care plan has experienced the same rapid growth in high-tech medical imaging utilization as federal health insurance programs.

The 377,000-member Group Health Cooperative's per-beneficiary use of high-tech imaging more than doubled from 1997 to 2006, according to researchers from GHC's Center for Health Studies and the University of California, San Francisco. Their findings were based on an analysis of more than five million imaging studies.

Data from the managed care group's automated information system identified across-the-board growth for CT, MR, and ultrasound regardless of patient age or sex or the anatomic target for imaging, according to principal author Dr. Rebecca Smith-Bindman, an associate professor of radiology at UCSF.

The persistence of the growth pattern suggests the likelihood of inappropriate imaging even in a managed care environment that lacks the incentives for overutilization abuses that have been associated with Medicare and fee-for-service imaging.

"That suggests to me that some of the increase is not directly related to patient symptoms," she said in an interview with Diagnostic Imaging.

Overall, cross-sectional imaging performed at hospitals and clinics owned and operated by GHC rose from 260 to 478 exams per beneficiary in the 10-year period. MRI increased 26% per year, from 22 to 72 exams per 1000 beneficiaries. CT increased 14% per year, from 81 to 181 exams per 1000. Ultrasound increased 5% per year, from 157 to 225 exams per 1000.

Imaging costs during the 10-year period doubled to $433 annually per beneficiary, according to Smith-Bindman and coauthors Dr. Eric Larson, executive director of the Center for Health Studies, and Diana L. Miglioretti, Ph.D., an associate investigator at the center.

Higher costs were attributed mainly to CT and MR. At the beginning of the study period, about 50% of the imaging costs stemmed from cross-sectional imaging. At the end, that portion had increased to 70%.

The growth rates were surprisingly consistent for CT and MR applications in the abdomen, central nervous system, spine, and chest. Total volumes varied for each application, but their growth rates were nearly identical, suggesting that some of the increases are not directly related to patient symptoms, Smith-Bindman said.

The study, published in the November/December issue of Health Affairs (2008;27[6]: 1491-1520), confirmed results of investigations by the Medicare Payment Advisory Commission and the Government Accountability Office. They showed that Medicare expenditures for outpatient imaging have increased at a double-digit annual rate since 2000.

Other findings in the Group Health Cooperative study confirmed long-standing suspicions about the additive nature of imaging technology. Investigators identified few instances of decreased utilization of a specific test accompanied by increased utilization of another exam designed to answer the same diagnostic question.

Smith-Bindman noted that chest CT can provide a better evaluation of pulmonary symptoms for suspected pulmonary emboli than standard chest x-rays and ventilation quantification nuclear scans, for example.

"We saw absolutely no decline in either chest x-rays or ventilation quantification nuclear scans concomitant with the increase in CT to rule out the possibility of pulmonary emboli," she said.

The study did not consider the effect of increased utilization on clinical outcomes, nor did it directly examine the clinical appropriateness of patient referrals for cross-sectional imaging. But the findings highlighted the need for guidelines to help physicians assess when specific imaging tests should be ordered, Smith-Bindman said.

The study offered separate sets of take-away messages for patients and physicians, she said. Patients should carefully consider the potential benefits and risks when their physician prescribes an imaging exam, and radiologists need to pursue more research that tests the clinical effectiveness of their work.

"We would rather have a decrease in unnecessary imaging and an increase in necessary imaging," she said. "It is incumbent on us to do the studies that demonstrate the value of what we do."

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