CT Perfusion and Angiography Fall Short as Standalone Tests for Brain Death

CT perfusion and angiography imaging did not meet the necessary diagnostic accuracy thresholds in terms of sensitivity and specificity to serve as standalone ancillary tests for determining death by neurologic criteria (DNC). The findings of a large, prospective, multicenter study published in JAMA Neurology suggest that clinical assessment remains essential for diagnosis of DNC even in settings where imaging is used to support the decision-making process.

The study evaluated 282 adults with acute and devastating brain injuries across 15 Canadian intensive care units (ICUs) who had a Glasgow Coma Scale (GCS) score of 3. The diagnostic accuracy in terms of sensitivity and specificity of 4 imaging modalities—qualitative and quantitative CT perfusion, CT angiography, and whole-brain CT perfusion—were compared against clinical diagnosis of DNC. To be considered validated for standalone use, both the specificity and sensitivity of a given imaging modality had to be greater than the prespecified validation threshold of 98%. Clinical diagnosis of DNC was conducted by 2 clinicians including neurologists, neurosurgeons, or intensivists who followed DND diagnostic criteria published in Neurology and the Canadian Medical Association Journal. The study’s primary end point was the diagnostic accuracy of CT perfusion of the brainstem based on qualitative and quantitative assessments, with results from other imaging modality tests comprising secondary end points.

None of the imaging tests met the prespecified validation threshold:

• Qualitative brainstem CT perfusion had an accuracy of 91.8% (95% CI, 88.0% to 94.8%) and exhibited a high sensitivity (98.5% [95% CI, 95.8% to 99.7%]) but low specificity (74.4% [95% CI, 63.2% to 83.6%]).
• Quantitative brainstem CT perfusion was not diagnostically accurate, with imaging of the midpons showing the highest sensitivity (36.1% [95% CI, 29.5% to 43.2%]) and imaging of the medulla showing the highest specificity (90.8% [95% CI, 81.9% to 96.2%])
• Qualitative whole-brain CT perfusion was 93.3% accurate (95% CI, 89.0% to 97.1%) with a sensitivity of 93.6% (95% CI, 89.3% to 96.6%) and a specificity of 92.3% (95% CI, 84.0% to 97.1%).
• The sensitivity of CT angiography ranged from 75.5% (95% CI, 69.0% to 81.2%) to 87.3% (95% CI, 81.9% to 91.5%), while its specificity ranged from 89.7% (95% CI, 80.8% to 95.5%) to 91.0% (95% CI, 82.4% to 96.3%).

The authors caution against relying solely on imaging in diagnosing DNC and advocate for continued use of rigorous clinical criteria as the diagnostic standard.