Radiologists are increasingly being challenged to do more with less: to care for more patients, to cover more hours of the day, to issue more detailed reports simultaneously, and to provide care at more sites . The higher workload has increased radiologists’ fatigue as well as the potential for committing diagnostic errors. Fatigue comes in many forms: physical, emotional, and cognitive. Given the nature of the interpretive task, visual fatigue is yet one more important form to consider in radiology .
Fatigue has been shown to contribute to errors in radiological diagnosis by decreasing radiologists’ accuracy . Over the past few decades, Dr. Krupinski et al. have contributed a great deal to the literature on factors that affect radiologists’ perception during the interpretive task. Krupinski et al. have shown that, after a day of clinical reading, there is a statistically significant decrease in the area under the ROC curve for identifying fractures on musculoskeletal radiographs , as well as pulmonary nodules on chest CT . In both studies, quantitative estimates of oculomotor strain and subjective assessments of fatigue were also higher after the clinical workday. Radiologists spent less time interpreting CT colonography exams later in the day as levels of fatigue rose . Residents at one institution had significantly higher rates of discrepancy with the final attending review during the last 2 hours of a 12-hour shift compared to the preceding 10 hours .
Cognitive errors in radiology include anchoring bias, framing bias, availability bias, and errors of perception, such as satisfaction of search . Satisfaction of search is a common type of perceptual error . It is the proverbial gorilla in the radiograph, but, instead of missing it entirely, we fixate on it and miss other, sometimes more subtle findings . Berbaum et al. demonstrated that satisfaction of search associated with presentation of a simulated pulmonary nodule on film-based chest radiographs resulted in a statistically significant decrease in the area under the receiver operating characteristic (ROC) curve . Samuel et al. used gaze tracking to show that simulated pulmonary nodules only received prolonged visual attention in the absence of native abnormalities on the film-based chest radiograph .
Prior studies using film radiographs interpreted on a light box postulated that satisfaction of search was due to decreased accuracy, specifically defined as a change in the height of the ROC curve . However, more recent studies from Dr. Krupinski’s group using digital images viewed on a workstation suggest that satisfaction of search is in fact secondary to a shift in the decision threshold, reflected by a change in both true positive fractions and false positive fractions . This type of change is noted to move points along the ROC curve, but not to shift the height of the curve itself. And despite the wealth of literature on the effects of fatigue—a system-based error—and satisfaction of search—a cognitive error—on the interpretative process in radiology, few studies have examined the interaction of the two effects . Dr. Krupinski et al. designed their latest study to specifically examine the mechanism of satisfaction of search in the setting of fatigue.
Satisfaction of search produced a threshold shift in the ROC curves for both faculty and resident readers, with a decrease in median true and false positive fractions. The authors interpret this as a decreased willingness to identify an abnormality. The threshold shifts were significantly more severe for residents than for the faculty in the satisfaction of search condition (ie, when a simulated pulmonary nodule was present). Interpretation times were not significantly different between the satisfaction of search and non-satisfaction of search conditions; a native abnormality was observed to require more interpretation time.
The authors have decades of experience in conducting perception research and, in particular, in studying the mechanisms of satisfaction of search. A robust study design was used, including standardized viewing conditions, a mix of faculty and trainee readers, a wide variety of chest radiography diagnoses, a randomization of case presentations, a counterbalanced design, and an appropriate washout period between reading sessions. However, one factor that was nonuniform was the degree of fatigue experienced by the readers before each session. All readers presented for study-related interpretation sessions after having completed at least an 8-hour clinical workday. However, the authors acknowledge that just over half of the readers spent the day interpreting only one type of modality, whereas the rest interpreted two or more types. Although this finding implies an inherent difference in the number and the type of clinical case interpreted before each study reading session, all clinical shifts were considered equivalent in terms of the degree of fatigue induced. It is realistic to wonder if some of the readers were in fact more fatigued than others because of a busier shift, recent on-call duties, or non–work-related factors. Unlike in prior work from this group, each reader’s degree of fatigue was neither subjectively nor objectively characterized before a study reading shift.
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