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To the Editor: After reading the thoughtful and provocative study by Dr Schriger and colleagues,¹ we came away unsure about the generalizability of their findings. The authors carefully showed that the accuracy of computed tomographic (CT) interpretation depended on the difficulty of scan type. The average correct score for interpretation ranged from 98% for "easy hemorrhages" to only 48% for "difficult acute infarctions." They also provided the frequency distribution of scan types shown to the physician readers. To evaluate the external validity of their results, however, we need to know the distribution of scan types for the general population of patients with acute stroke, not just the patients in their protocol library.

The estimate of overall accuracy hinges on this information. If easier scans are more heavily represented in practice than in the study population, then physicians' overall accuracy in CT interpretation is likely better than what the authors report. . . . [Full Text of this Article]