2005 to 2014 CT and MRI Utilization Trends in the Context of a Nondenial Prior Authorization Program

Reducing unnecessary testing may benefit patients, as some computed tomography (CT) and magnetic resonance imaging (MRI) expose patients to contrast, and all CTs expose patients to radiation. This observational study with historical controls assessed shifts in CT and MRI utilization over a 9-year period after a private health insurer's implementation of a nondenial, consultative prior authorization program.

Normalized rates of exams per 1000 person-years were plotted over 2005 to 2014 for people with commercial and Medicare Advantage health plans in the San Antonio market, with 2005 utilization set as the baseline. The program was implemented at the start of 2006. Computed tomography and MRI utilization changes were compared with contemporaneous changes in low-tech plain film and ultrasound utilization.

Growth in high-tech imaging utilization decelerated or reversed during the period. In 2006, CT utilization dropped to between 76% and 90% of what it had been in 2005, depending on the plan. In 2014, it was between 52% and 88% of its initial level. MRI utilization declined to between 86% and 94% of its initial level in 2006, and then to between 50% and 75% in 2014. Ultrasound utilization was greater in 2014 than in 2005 for some plans. Plain film utilization declined between 2005 and 2014 for all plans.

There was an immediate and sustained decline in CT and MRI utilization after the introduction of the program. While many factors may have impacted the long-term trends, the mixed trends in low-tech imaging suggest that a decline in low-tech imaging was not responsible for the decline in CT and MRI utilization.