Primary care docs use more CT

Jun 3, 2008

While most primary care physicians know that their CT utilization has increased in recent years, most are unaware of the extent of the increase.

A study from the Kaiser Foundation Hospital and the University of Hawaii's John A. Burns School of Medicine, both in Honolulu, found that CT utilization within five physician groups -- emergency medicine, internal medicine, family practice, ob/gyn, and pediatrics -- increased 28% from 2002 to 2006.

The study reviewed both the perceived and actual changes in CT ordering patterns from an HMO whose membership was stable during that five-year period. The HMO has no specific restrictions on CT utilization, and its total number of CT scanners remained the same from 2002 to 2006.

"Only data on chest, abdomen, pelvis, and spine CT were considered, since these lead to the largest radiation exposure for patients," said study co-author Michael Semenza, a fourth-year medical student at the University of Hawaii.

Physician questionnaire

To study CT utilization patterns, the researchers sent a survey with two questions to the doctors. This included answering "yes" or "no" to the following query: "Did you order more CT scans on a per patient basis in 2006 than in 2002?" The survey's response rate was 75%.

The study, presented at the 2008 American Roentgen Ray Society (ARRS) meeting, tallied an increase of 28% in CT utilization from 2002 to 2006. There were 4,581 CT scans performed in 2002, compared with 5,852 in 2006. In both 2002 and 2006, emergency medicine physicians, family practitioners, and internal medicine doctors accounted for approximately 95% of all CT scans.

CT utilization from 2002 to 2006

Family practice	+66.2%
Ob/gyn	+34.0%
Emergency medicine	+31.6%
Internal medicine	+14.3%
Pediatrics	-32.3%

Perceived increased CT utilization from 2002 to 2006

Emergency medicine	+84.6%
Family practice	+64.3%
Internal medicine	+56.4%
Pediatrics	+37.0%
Ob/gyn	+19.0%

Source: Kaiser Foundation Hospital and University of Hawaii's John A. Burns School of Medicine

The number of scans per 1,000 HMO members increased by 36%, from 24.2 scans per 1,000 members in 2002 to 33.3 scans per 1,000 members in 2006. "Once again," Semenza said, "pediatricians were the only ones to show a decrease of 28%."

When records of CT orders were reviewed from 2002 and 2006, 89% of emergency department physicians, 86% of family practitioners, 67% of ob/gyn physicians, 59% of internal medicine doctors, and 37% of pediatricians actually ordered more CT scans in 2006 than they did in 2002.

Each primary care group underestimated their increase in CT utilization, with the exception of pediatricians, who slightly overestimated their increased use. "The largest discrepancy we found was among obstetricians," Semenza said. "Roughly 20% believe they had increased utilization. In actuality, close to 66% had increased their utilization of CT."

Ob/gyn physicians represent only 2.2% and 2.4% of the total number of scans performed in 2002 and 2006, respectively.

Study limitations

Semenza acknowledges that the study's results may be limited by two factors. "Our primary care physicians may have underreported the number of CT scans ordered in the HMO because our survey was not completely anonymous," he said. "Second of all, our primary care physicians currently do not receive reports on CT utilization and their responses may have been 'guesswork' at times."

In their CT utilization survey, the researchers also asked the doctors to rate four different factors that might cause them to order a CT exam: