When patients experience blunt neck injuries—after a car accident, for example—follow-up MRI is not necessary after a CT scan comes back negative for spine instability, according to a new study published in JAMA Surgery.

“The primary reason for performing MRI in patients with blunt trauma is to look for instability that may need a cervical collar or surgical fixation for immobilization,” wrote author Ajay Malhotra, MD, MMM, department of radiology and biomedical imaging at the Yale School of Medicine in New Haven, Connecticut, and colleagues. “We conducted this study to assess pertinent factors that might affect decision making regarding the role of MRI and its cost implications by comparing the two follow-up strategies.

The authors performed a cost-effectiveness analysis using data from CMS, the National Spinal Cord Injury Database and other recent studies. Overall, in the case of an average 40-year-old patient with blunt trauma, the cost of MRI follow-up was more than $14,000 with a health benefit of 24.02 quality-adjusted life-years (QALY). The cost of no follow-up was more than $1,000 with a benefit of 24.11 QALY.

“Magnetic resonance imaging had a lower health benefit and a higher cost compared with no follow-up after a normal CT finding in patients with obtunded blunt trauma to the cervical spine, a finding that does not support the use of MRI in this group of patients,” the authors wrote. “The conclusion is robust in sensitivity analyses varying key variables in the model. More literature on these key variables is needed before MRI can be considered to be beneficial in the evaluation of obtunded blunt trauma.”

Malhotra et al. noted that the cost of MRI could have actually been much higher had they included the costs associated with patients undergoing surgery after false-positive MRI findings. “The proportion of patients undergoing surgery after a false-positive MRI finding could be challenging to estimate accurately; thus, we assumed that all patients would only be given cervical collars in the model, with lower cost and mild disutility,” they wrote. “The cost of the MRI strategy would be significantly higher, and effectiveness lower if operations were taken into account in place of cervical collar immobilization.”