Objective Patients diagnosed with psoas abscess have a high mortality rate. The major cause of its poor prognosis is delayed treatment. Therefore, making a correct diagnosis rapidly is important. Both computed tomography (CT) and magnetic resonance imaging (MRI) are considered to be the gold standards as imaging modalities that have a high sensitivity for detecting psoas abscess. There have been few reports regarding the limitations of these methods, but psoas abscess in its early stage may go undetected by CT and MRI. Methods Detection of psoas abscess by CT and MRI was investigated in the present study through a retrospective review of 15 patients in whom psoas abscess was diagnosed during a course of ten years at our hospital. Results In all patients, psoas abscess was diagnosed by at least a plain CT, enhanced CT, and/or plain MRI. The interval between the onset of symptoms and diagnosis was 20.9±17.9 days (mean ± standard deviation). In three patients, repeat imaging identified a psoas abscess, whereas initial imaging failed to detect it. The overall sensitivity of plain CT, enhanced CT, and plain MRI for psoas abscess was 78%, 86%, and 88%, respectively. From six days after the onset of symptoms, the sensitivity of each modality was 100%, while the sensitivity from day one to five days was only 33%, 50%, and 50%, respectively. Conclusion Although CT and MRI are considered to be gold standard modalities for diagnosing psoas abscess, both methods can fail to notice this condition in its early stage.

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ObjectiveDiagnosis of community-acquired pneumonia (CAP) in the elderly is often delayed because of atypical presentation and non-specific symptoms, such as appetite loss, falls and disturbance in consciousness. The aim of this study was to investigate the external validity of existing prediction models and the added value of the non-specific symptoms for the diagnosis of CAP in elderly patients.DesignProspective cohort study.SettingGeneral medicine departments of three teaching hospitals in Japan.ParticipantsA total of 109 elderly patients who consulted for upper respiratory symptoms between 1 October 2014 and 30 September 2016.Main outcome measuresThe reference standard for CAP was chest radiograph evaluated by two certified radiologists. The existing models were externally validated for diagnostic performance by calibration plot and discrimination. To evaluate the additional value of the non-specific symptoms to the existing prediction models, we developed an extended logistic regression model. Calibration, discrimination, category-free net reclassification improvement (NRI) and decision curve analysis (DCA) were investigated in the extended model.ResultsAmong the existing models, the model by van Vugt demonstrated the best performance, with an area under the curve of 0.75(95% CI 0.63 to 0.88); calibration plot showed good fit despite a significant Hosmer-Lemeshow test (p=0.017). Among the non-specific symptoms, appetite loss had positive likelihood ratio of 3.2 (2.0–5.3), negative likelihood ratio of 0.4 (0.2–0.7) and OR of 7.7 (3.0–19.7). Addition of appetite loss to the model by van Vugt led to improved calibration at p=0.48, NRI of 0.53 (p=0.019) and higher net benefit by DCA.ConclusionsInformation on appetite loss improved the performance of an existing model for the diagnosis of CAP in the elderly.

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