Location, location, location: Disparity in CT use suggests gaps in evidence-based guidelines

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CT scan use in N.Y. state hospitals varied by 20 percent, according to a study published online in March in the American Journal of Managed Care. The researchers also reported a surprise finding: little difference in CT utilization between teaching and nonteaching hospitals.

Although CT utilization has swelled in the last two decades, questions about overuse and underuse remain. Geographic analysis offers a method to build understanding of care patterns, technology use and small-area variations in healthcare. However, it has not been employed in the study of CT imaging.

Eric A. Vance, PhD, from the department of statistics at Virginia Polytechnic Institute and State University in Blacksburg, Va., and colleagues conducted a geographic analysis to examine patient, hospital and geographic characteristics influencing variation in CT use in N.Y. inpatients.

The researchers relied on the 2007 edition of the N.Y. State Inpatient Database from the Healthcare Cost and Utilization Project and analyzed approximately 2.49 million inpatients from 221 hospitals in 56 counties.

A total of 28 percent of inpatients underwent at least one CT exam. The top two strongest predictors of the likelihood of CT scanning were an inpatient’s diagnosis and age, with CT scanning generally increasing with age. Trauma was the most likely diagnosis to result in a CT scan.

The top two counties for CT imaging performed exams on 37.4 percent and 37.2 percent of inpatients, while the lowest rates of scanning were 17 percent and 17.3 percent, respectively.

“Identifying factors that may explain the residual variability is important for developing interventions and managing care to ensure the appropriate use of this important technology… Although certain characteristics such as age or diagnosis cannot be modified, interventions informed by evidence-based guidelines or protocols can help to enforce appropriate CT scan use and can ultimately reduce variation and improve healthcare value,” wrote Vance et al. Continuing education and peer review also might help smooth the variation, according to the authors.

Commenting on the unexpected finding of only minor differences in CT utilization between teaching and nonteaching hospitals, the researchers suggested the possibility that protocols and guidelines for CT use had been applied in the teaching sites. Stronger adherence to evidence-based guidelines might override factors that would drive CT use, such as the tendency of medical trainees to order scans and service of a patient population with more comorbid diagnoses and less access to healthcare.

Practical insights provided by a geographic analysis can help ensure access to CT services while avoiding oversupply, Vance and colleagues concluded.