Variation in Utilization of Computed Tomography Imaging at Tertiary Pediatric Hospitals

Discussion

This study illustrates the marked variability in the use of CT imaging across tertiary pediatric institutions. Overall, the use of CT imaging decreased from 2009 to 2013, but unadjusted rates of CT scanning varied nearly 4-fold between the hospitals with the lowest and highest scanning rates. Case-mix (APR-DRGs and severity levels) accounted for 49% of the variability across institutions, and hospital volume accounted for an additional 15% of the remaining variability, with higher volume hospitals scanning at lower rates. Therefore, 36% of the variability in the use of CT imaging across hospitals remains unexplained. This finding suggests that 36% of the variability in CT scan rates may be due to differences in institutional or clinician practices, and it represents a potential opportunity to reduce CT imaging through multi-institutional quality improvement projects.

Each of the included institutions in this study is a large children’s hospital in a metropolitan area that sees a diverse patient population; however, the wide variability in the rate of CT imaging was consistent across encounter type, suggesting that differences in scan rates are due to institutional differences in clinical practice. There was also a significant and positive correlation between inpatient/observation scan rates and treat-and-release ED scan rates, which suggests that institutions with higher CT utilization will have higher scan rates across encounter types. Moreover, the rate of CT use decreased with increasing hospital volume, suggesting that higher volume hospitals may be more likely to use other diagnostic methods or institute alternative practices.

Our data reveal an overall average decrease in the rate of CT scanning of 5.6% per year. Hospitals with the highest rates of CT imaging in 2009 exhibited the largest absolute decreases during the study period. Head and abdomen/pelvis imaging decreased roughly the same amount across the study period (6.7% and 5.8% per year, respectively), suggesting that the decrease in CT use is due to a global reduction in scans. Some hypothesized reasons for this decline include increased media attention, the national educational campaign of Image Gently,^14–16 and clinical decision guidelines^17,18 that raised awareness for minimizing ionizing radiation exposure in children. Efforts to implement multi-institutional standards and protocols to reduce variation in the prescribing of CT scans may decrease variability and improve overall care. Previous collaborative efforts across pediatric institutions in critical care and surgery have been shown to be both feasible and successful.¹⁹

Our study characterizes the variability in CT scan rates across tertiary pediatric hospitals for ED, inpatient, and observation encounters and is inclusive of all body regions. Previous multi-institutional pediatric studies on CT utilization focused on ED encounters. One study using PHIS reported an overall decrease in CT imaging and a 3-fold interhospital variability in the use of CT scans for head trauma in pediatric EDs from 2005 to 2009,¹² which was similar to the extent of variability found in the present study. Another study reported no change in overall CT scan rates for all indications in 2 tertiary pediatric hospital EDs from 2003 to 2010.²⁰ In this latter study, CT scan rates decreased between 2008 and 2010, although the significance of this trend was not statistically tested. Lastly, a study that examined national trends in CT scan rates in the ED from 1995 to 2008 found a steady increase in scan rates over this period, with no difference in rates between pediatric and nonpediatric EDs.²¹ In contrast, our findings demonstrate that pediatric CT scan rates have decreased in recent years but vary widely across institutions.

The present study has several limitations. First, this analysis includes data from only 30 tertiary care children’s hospitals that submitted complete ED, inpatient, and observation data to PHIS during the study period. It is unclear whether these findings would be generalizable; however, our results likely represent a best-case scenario because the included centers are focused on pediatric care and were more likely to have clinical care protocols and 24-hour availability of alternative evaluation methods such as pediatric ultrasound or MRI. Second, because PHIS is an administrative database, there is inevitably some misclassification of data that could potentially affect these results. In particular, it was not always clear whether multiple CTCs for CT scans on the same day represented distinct radiation exposure events. To produce conservative estimates of scanning rates, we assumed that scans of the same body region performed on the same day represented a single exposure event unless the exact same scan was billed multiple times (eg, multiple head scans on the same day were counted as distinct scans). Third, it is possible that some PHIS hospitals would have had more transfers in which imaging had already been performed at a referring hospital. The impact of transfer status cannot be assessed due to the unreliability of the source of admission data element in PHIS. However, given that all PHIS hospitals are tertiary children’s hospitals, we would expect all of them to have relatively high incoming transfer rates. Fourth, data were missing on some of the variables that were included in our analyses, but this omission is expected to have had minimal effect on our findings because <2% of scans had any missing data. Finally, additional differences in case-mix, beyond those accounted for by using APR-DRGs and severity levels, may exist that could explain some of the remaining variability in scan rates.