Yield and clinical predictors of thoracic spine injury from chest computed tomography for blunt trauma.

INTRODUCTION

Cost and radiation risk have prompted intense examination of trauma patient imaging. A proposed decision instrument (DI) for the use of chest computed tomography (CT), (CCT) in blunt trauma patients includes thoracic spine (TS) tenderness, altered mental status (AMS) and distracting painful injury (DPI) as potential predictor variables. TS CT is a separate, costly study whose value is currently ill-defined. The objective of this study is to determine test characteristics of these predictor variables alone, and in combination, to derive a TS injury DI.

METHODS

Prospective cohort study of blunt trauma patients age > 14 in a Level I Trauma Center who had either CCT or TS CT.

RESULTS

Of 1,798 blunt trauma patients, 1,174 (65.3%) had CCT, and 46 (2.6%) had a TS CT at physician discretion. CCT identified 58 TS injuries in 1,220 patients (4.8%). For 1,032 patients without AMS, 18/35 had TS tenderness, for sensitivity of 51.4%, specificity 84.7%, positive (PPV) and negative predictive values (NPV) of 10.5% and 98.0%. Positive likelihood ratio (+LR) was 3.35, with negative (-LR) 0.57. Among the 58 TS injuries, 23 had AMS for sensitivity of 39.7%, with other test characteristics of 85.8%, 12.2%, 96.6%, with +LR 2.79 and -LR 0.70. Thirty-eight of 58 had DPI, for sensitivity 65.5%, with other test characteristics 65.7%, 8.7%, and 97.4%, with +LR 1.91 and -LR 0.52. Combining 3 predictor variables into a proposed DI found 56/58 injuries for test characteristics of 96.6% (95% CI 88.1-99.6%), 49.1% (46.1-52.0%), 8.6% (6.6-11.1%) and 99.7% (CI 98.7-100%), with +LR 1.90 (1.76-2.04) and -LR 0.07 (0.02-0.28). If validated, the DI would exclude 572/1,220 CCT patients from separate TS CT (46.9%, CI 44.1-49.7%), and 141/511 (27.6%, CI 23.8-31.7%) patients who actually had TS CT in our cohort. Medicare payment at our center for sagittal reconstructions of TS CT is $280 for professional plus technical charges ($3,312 per study). The DI, if validated, would save $39,000-$160,000 in TS imaging payments.

CONCLUSION

TS CT is low yield and costly. Patients who are alert, have no TS tenderness and no DPI have a very low likelihood of TS injury (NPV 99.7% 95% CI lower limit 98.7%) with -LR=0.07, 95% CI upper limit 0.28). Avoiding TS CT may save considerable charges and payments.