大杉 泰弘

OBJECTIVES: Diagnostic errors are caused by disease complexity, variable settings in which care is provided, and multiple cognitive and system-level factors. However, whether outpatient diagnostic errors aggregate into specific failure modes that align with the clinical context remains unclear. Therefore, we aimed to explore these modes by examining the salient causes of unexpected readmission. METHODS: We conducted a cross-sectional study to analyze unexpected readmissions among outpatients in general internal medicine who visited a clinic within 14 days of their initial visit. Two physicians independently assessed the diagnostic errors using the Revised Safer Dx Instrument and Diagnostic Error Evaluation and Research (DEER) taxonomy. We applied hierarchical clustering to the DEER taxonomy and conducted Fisher's exact tests to examine the associations with patient, physician, and system factors (presence of a referral letter, personal protective equipment [PPE] use, and late session). RESULTS: Among the 146 patients, 50 (34.2 %) experienced diagnostic errors. Cluster analysis revealed two main categories of failure modes: (1) diagnostic prioritization and urgency appraisal failure, and (2) information acquisition and synthesis failure. The latter category was further divided into three clinically relevant subtypes: data-gathering failure, where PPE use was more common; information synthesis and interpretation failure, in which referral letters were more common; and undertesting and safety-netting failure. CONCLUSIONS: We identified that diagnostic errors were divided into four diagnostic failure modes that mapped to distinct DEER failure patterns and other factors. Linking these failure modes to measurable contextual variables may provide targets for diagnostic safety programs.

The superior aortic recess, a normal pericardial extension around the ascending aorta, can be misinterpreted as pathological findings on imaging studies, potentially leading to misdiagnosis of conditions such as Takayasu arteritis. We report a case of persistent fever and joint pain initially suspected of having Takayasu arteritis based on contrast-enhanced CT showing apparent aortic wall thickening. Laboratory tests showed elevated inflammatory markers (CRP: 7.07 mg/dL, WBC: 11,200/μL), microcytic anemia (hemoglobin: 7.8 g/dL), and thrombocytosis (platelets: 599,000/μL). Initial treatment with nonsteroidal anti-inflammatory drugs, sulfasalazine, and low-dose prednisolone was ineffective. Although contrast-enhanced CT suggested aortic wall thickening, a fluorodeoxyglucose positron emission tomography scan/CT revealed no uptake in this area, making a diagnosis of Takayasu arteritis unlikely. Radiological reassessment identified the structure as the superior aortic recess rather than aortic wall thickening, and the patient fulfilled Yamaguchi's criteria for adult-onset Still's disease with markedly elevated ferritin (3,459 ng/mL). Treatment with prednisolone 60 mg daily and subsequent addition of tocilizumab 480 mg weekly led to complete symptom resolution and normalization of laboratory parameters. This case highlights the importance of recognizing normal anatomical variants in radiological interpretation to avoid misdiagnosis, emphasizing the need for comprehensive diagnostic approaches incorporating clinical, laboratory, and appropriate imaging findings to distinguish between vascular pathologies and normal anatomical variants.