NEXUS Chest CT Decision Instrument for CT Imaging

Why did you develop the NEXUS Chest CT Decision Instruments (DI)? Was there a clinical experience that inspired you to create this tool for clinicians?
Our development of the NEXUS Chest CT DIs arose during our original NEXUS CXR study work. At this time (around 2005-2008), we noted that chest CT was becoming increasingly common -- both independently and as part of head-to-pelvis CT (pan-scan). Compared to CXR, chest CT is much more expensive and is associated with radiation to radiosensitive anatomical regions, which may induce cancer in the disproportionately young trauma population. We performed a study that demonstrated low yield of trauma chest CT for clinically significant injury in certain scenarios that further pushed us to perform our chest CT DI development work.

What pearls, pitfalls and/or tips do you have for users of the NEXUS Chest CT DI? Are there cases when they have been applied, interpreted, or used inappropriately?
Two pitfalls: First, these DIs are intended to be used in awake, non-intubated, hemodynamically stable, adult (15 years or older) trauma patients—NOT critically ill, severely injured, poly-trauma patients or for intubated patients. To apply these DIs, clinicians have to be able to assess whether patients have criteria, such as chest wall or sternal tenderness.

Second, these are one-way rules that only tell you whether CT may be safely omitted, and you should only apply NEXUS Chest CT in patients that you initially believe to need chest CT. The presence of 1 or more DI criteria does not dictate the need for chest CT in patients who would not otherwise be imaged. Misapplication of these DIs to other patients who were not being considered for CT may paradoxically lead to unnecessary increases in imaging.

In terms of pearls we have 3:

1. In developing these DIs, we were very cognizant of time pressures and mental work-load associated with implementation of complicated decision rules. All of our criteria are very simple elements of the standard trauma history and physical exam that should not take extra time. For ease of use the 4 physical exam criteria (chest wall, sternum, thoracic spine and scapula tenderness) may be simply lumped together as any bony tenderness of the thorax or upper back.
2. We also recognized inherent differences in opinion regarding the need to diagnose minor thoracic injuries. We therefore developed 2 DIs: For clinicians who believe that nearly all injuries should be detected, we recommend the “All” DI, which detects both clinically major and minor injuries with high sensitivity. For those who believe that only management-changing injuries are important, we recommend “Major”, which retains very high sensitivity for clinically major injuries (with slightly lower sensitivity for minor injuries). Major has higher specificity, thereby sparing a larger number of patients from CT.
3. We recommend the incorporation of the NEXUS Chest DIs and algorithm as checklists into chart templates and electronic medical records to further streamline and simplify clinicians' decision-making.

What recommendations do you have for healthcare providers once they have applied the NEXUS Chest CT DI? What are the next steps?
In terms of charting or documenting their decision-making, clinicians may state that a “patient meets NEXUS Chest CT low risk criteria for injury” or “patient ruled out for significant thoracic injury by NEXUS Chest CT” in a manner similar to that used with the NEXUS Cervical Spine or other decision rules.

How does the NEXUS Chest CT DI compare with your NEXUS chest DI for blunt trauma?
Our NEXUS Chest DIs (NEXUS CXR and NEXUS Chest CT) are meant to be used sequentially. For most patients we recommend first applying NEXUS CXR. If a patient is deemed low risk by this NEXUS CXR, then no imaging (neither CXR nor chest CT) is recommended. If chest CT is being considered after CXR, then apply NEXUS Chest CT to determine whether CT may be safely omitted.

Any other comments on the NEXUS Chest CT DI?
Overall, our NEXUS Chest DIs provide clinicians with evidence-based mechanisms to use basic physical exam and history findings for selective imaging, instead of reflexive imaging, to safely and efficiently rule out injury in appropriate patients. By safely eliminating the need for imaging upfront, our DIs and algorithm will decrease costs, save provider and patient time, and decrease unnecessary radiation exposure.

Robert Rodriguez, MD, is a professor of clinical emergency medicine and the residency research director at UCSF School of Medicine. He is also an attending emergency room physician. Dr. Rodriguez's research interests include deriving decision instruments for imaging in blunt trauma, critical care in the ED, infectious disease presentations to the ED, homeless and immigrant population access and care in the ED, and defensive medicine.