and appropriate treatment (therapeutic yield). The degree to which appropriate treatment can improve patient outcomes depends on its efficacy (treatment efficacy). In a trial evaluating the effect of fluorescence cystoscopy on the recurrence of bladder carcinoma in situ, the enhanced accuracy of fluorescence cystoscopy compared with white light cystoscopy alone led to a substantial increase in lesions being identified and treated at initial diagnosis, which significantly reduced the rate of recurrence. 13 Diagnostic and therapeutic confidence Although diagnostic yield generally increases with accuracy, it is also affected by a doctor's confidence in the diagnostic test. Tests inducing greater confidence could benefit patients by reducing the need for further investigations and shortening the time to treatment. The results of a trial evaluating the triage of patients with non-small cell lung cancer who were referred for operative staging with positron emission tomography (PET), show how a lack of diagnostic confidence can over-ride the benefits of improved accuracy. 14 PET identified patients for whom surgery was not indicated because of incurable mediastinal disease, but no difference was found in the proportion of patients avoiding a thoracotomy (the primary outcome) because surgeons still preferred to confirm PET findings using standard operative staging. Doctors' confidence in the ensuing success of a treatment plan can affect treatment effectiveness by influencing the approach to treatment, particularly in surgery. Digital subtraction angiography (DSA) and multidetector row computed tomographic angiography (MDR-CTA) can both determine the location and degree of vascular narrowing in patients with symptomatic hardening of peripheral arteries.