Chest roentgenograms in diagnosis of traumatic rupture of the aorta. Observer variation in interpretation.

A significant p value is not always a good measure of the clinical value of a diagnostic test. By examining interobserver agreement with respect to chest roentgenogram interpretation, we determined which of seven roentgenographic signs statistically associated with traumatic rupture of the aorta (TRA) are most likely to be useful in clinical practice. Four surgeons and two radiologists were asked to interpret individually, in blinded fashion, the initial chest films of 149 trauma patients who had undergone aortography to rule out TRA. Agreement between all observers, as well as between specialty groups, was examined by chi-square and by calculation of Cohen's kappa statistic, which estimates the extent of agreement. Statistically significant agreement (p = .0000) was found between all observers with regard to mediastinal widening and obscuration of the aortic knob, but other comparisons showed no better than random agreement. Of the seven roentgenographic signs associated with TRA, identification of mediastinal widening and obscuration of the aortic knob show the most consistent interobserver agreement and are the most likely to be useful in clinical practice.