Despite major national investments in HIE, its effect on quality and costs is not well documented. This study is among the first to study the effect of HIE in the emergency setting. Our research demonstrates that HIE is associated with increased adherence with evidence-based guidelines and reduced use of diagnostic neuroimaging for headache. Consistent with other research, we found low HIE use rates.6,26
HIE was accessed for repeat headache visitors only 21.9 % of the time. Previous research suggests that low use is related to both system factors and time constraints.27,28
Despite low use of the HIE system, we estimate—based on the number of diagnostic CT scans obtained in the study population and the odds of neuroimaging with HIE—that HIE use resulted in the avoidance of 163 head CTs in a two-year period. If HIE had been used in all cases we estimate that as many as 748 CT scans could have been avoided.
This study documents that over two-thirds of repeat visitors to the ED for headache received a head CT. This is consistent with numerous studies documenting increasing rates of CT scan use. In 2006 an estimated 19 million CT scans were performed in the US.29
Head CTs in the ED increased 51 % from 2000–2005 and 13 % of all ED encounters received a head CT.15
National guidelines suggest a high percentage of these CT scans are unnecessary. CT and MRI neuroimaging are very low yield and costly in chronic headache patients with no other neurological findings on exam.30,31
Our study demonstrates that many CT scans could be avoided by making patient records available through HIE.
Our study also found that more than 15 % of ED patient-visits for headache were made by repeat visitors some of whom had as many as 46 previous visits to multiple EDs for headache in a two-year period. Other studies show that although only 1 % of severe headache patients are frequent ED visitors, frequent visitors account for 51 % of all ED visits.16
Recurrent CTs place these frequent ED visitors at increased health risk from radiation exposure.32
For these frequent visitors less is more: fewer head CTs often means better care. Although we were unable to assess potential harms resulting from reduced CTs with HIE use, given our stringent inclusion criteria, it is unlikely that the repeat visitors for primary headache disorders included in the study would have experienced benefits from a CT through the detection of a unsuspected mass or hemorrhage.
Overall HIE use was not associated with a reduction in costs of emergency care for headache in this study. This finding is likely secondary to confounding by indication; providers chose to access the HIE for patients posing greater diagnostic challenges. Post-hoc analysis demonstrated that patients in whom physician/NPs chose to use HIE had higher Charlson index comorbidity scores. And a previous cross-sectional survey of providers using the MSeHA HIE confirms that providers access HIE data primarily for problematic clinical cases.27
Even though fewer CT scans were obtained and guidelines were more frequently followed when physician/NPs used the HIE, analysis revealed that higher costs associated with overall HIE use and HIE use by physician/NPs were driven by increased use of MRI when physician/NPs used HIE on an “as needed” basis. Alternatively, systematic HIE use by administrative/nursing staff was associated with larger cost savings. This suggests that the way HIE is used matters. Further controlled studies are needed to explicitly test whether certain ways of employing HIE are more effective in improving quality and decreasing costs.
The implications of the current study are significant. This study is among the first to demonstrate that HIE reduces potentially avoidable neuroimaging, improves adherence with guidelines, and thereby protects patients from harm. The one previous randomized trial of HIE did not assess use of diagnostic tests.4
Frisse’s case–control study of the MidSouth eHealth Alliance in Tennessee similarly demonstrated overall reductions in diagnostic testing with HIE but lacks specificity and merits replication in homogeneous disease-specific populations.5
One-third of diagnostic CT studies in adults are of the head exposing the adult brain to approximately 20 mSV of radiation.17
As much as 2 % of all cancers in the United States may result from the use of CT scans.17
This study demonstrates that HIE is associated with reduction of head CTs by 50 % in patients at high risk for repeated scans. Such major potential benefit provides strong support for HIE adoption.
Reduction in risk of adverse consequences of ionizing radiation by HIE does not come at the consequence of decreased quality of care. To the contrary, the current study demonstrates that HIE in combination with number of previous visits is associated with a 65 % increase in odds of guideline adherence. This study suggests that HIE is an important tool that supports physicians in delivering evidence-based care.
The current study is subject to the usual limitations inherent in epidemiological studies. The associations seen between HIE use and diagnostic testing, guideline adherence, and costs are not necessarily causal. We were unable to adjust for potential physician-level effects, and it is possible that physician characteristics associated with their propensity to use HIE could account for some of the effects seen. Only a randomized clinical trial of HIE use would fully eliminate this potential source of bias. However, increased propensity of providers to use HIE for more complex patients would be expected to diminish the effect of any HIE use, making the demonstrated positive effects of HIE use more remarkable.
The evidence-based guideline algorithm employed may have overestimated non-adherence. We were unable to exclude certain important headache presentations such as "thunderclap", "worst", or "pattern change" that can justify imaging from the non-adherence group. However, this potential bias should not have applied differently to cases with and without HIE use. Our study may also underestimate cost savings associated with HIE. Only ED visit and imaging information was used to impute costs based on standard Medicare reimbursement rates and other costs were not considered. Additionally, since Medicare reimbursement rates are lower than those of other payers, the reported cost savings are very conservative. Average U.S. costs are $1,150 for CT and $2,550 for MRI33
compared with Medicare reimbursement rates of approximately $300 for CT and $500 for MRI. Although we estimate that HIE use by administrative/nursing staff was associated with a modest cost savings, the true potential cost savings may be significantly higher.
Many professional groups advocate HIE based on perceived potential benefits2,3
However, this study is among the first to demonstrate significant benefits associated with investment in HIE. This study suggests that ongoing federal support for HIE is warranted, but that funding should be tied to ongoing demonstration of meaningful HIE use.34
Further studies are needed to assess alternative methods for improving HIE use and to determine the effect of HIE on potentially avoidable testing and admissions, guideline adherence, and costs in other disease-specific patient populations. Reducing potentially avoidable diagnostic imaging through HIE represents an opportunity to improve quality and patient safety. HIE is proving an important resource to assist practitioners by providing critical patient information at the right time and place to enhance patient care and reduce unnecessary healthcare spending.