Efficacy of diagnostic X-ray examination

To the Editor.— The article by Fineberg et al (238:224, 1977) on an efficacy type study of computerized cranial tomography prompts me to point out that a large-scale study of the efficacy of diagnostic x-ray examination has been in progress since 1971 as an activity of the American College of Radiology (ACR) Committee on Efficacy Studies. Two of the ideas used by Fineberg were developed and pilot tested during 1971 to 1973 by Thornbury, Edwards, and Fryback at the University of Michigan for the ACR efficacy study: first, that efficacy should be defined as levels in a hierarchy and, second, that the impact of diagnostic test information on the physician's diagnostic opinion could be measured in terms of the physician's probability assessments of diagnoses. A final report on the first phase (efficacy 1, defined as diagnostic thinking efficacy or diagnostic efficacy) of the ACR efficacy study has been completed. Since