Detection of early CT signs of >1/3 middle cerebral artery infarctions : interrater reliability and sensitivity of CT interpretation by physicians involved in acute stroke care.

BACKGROUND AND PURPOSE: This study had 2 goals: (1) to assess interrater reliability of academic neuroradiologists when classifying acute infarction by CT scan as >1/3 middle cerebral artery (MCA) involvement, <1/3 MCA involvement, or no infarction and (2) to determine the sensitivity of physicians potentially involved in acute stroke treatment in detecting >1/3 MCA acute infarctions. Studies of tissue plasminogen activator show an association between early signs of major infarction and poor outcome. The American Academy of Neurology and the American Heart Association recommend avoiding thrombolysis if early signs of major infarction are present.

METHODS: We presented 25 scans (normals, acute infarctions, and old infarctions) to 3 academic neuroradiologists. A scoring sheet based on Alteplase Thrombolysis for Acute Noninterventional Therapy in Ischemic Stroke (ATLANTIS)/CT Summit criteria was used to determine >1/3 MCA territory involvement. Nine of the 25 scans were presented again to assess intrarater reliability. We recalculated results of our previous study in which physicians interpreted infarction scans, now designating the scans as >1/3 MCA, <1/3 MCA, or normal, as determined by the neuroradiologists.

RESULTS: All 3 neuroradiologists agreed on no infarction, <1/3 MCA, and >1/3 MCA on 64% of the scans. Neuroradiologist test-retest agreement was 96% for >1/3 MCA territory. Overall sensitivity for emergency physicians, neurologists, and general radiologists for detecting the presence of infarction in scans rated as >1/3 MCA was 78%.

CONCLUSIONS: Neuroradiologists can achieve moderate agreement in detecting >1/3 MCA infarction. The emergency physicians, neurologists, and general radiologists tested were reasonably skilled at detecting >1/3 MCA acute infarction. However, their performance did not reliably identify all patients who have early CT infarct signs that place them at increased risk for cerebral hemorrhage after thrombolytic therapy.