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INTRODUCTION: Clinical reasoning in diagnostic imaging professions is a complex skill that requires processing of visual information and image manipulation skills. We developed a digital simulation-based test method to increase authenticity of image interpretation skill assessment. METHODS: A digital application, allowing volumetric image viewing and manipulation, was used for three test administrations of the national Dutch Radiology Progress Test for residents. This study describes the development and implementation process in three phases. To assess authenticity of the digital tests, perceived image quality and correspondence to clinical practice were evaluated and compared with previous paper-based tests (PTs). Quantitative and qualitative evaluation results were used to improve subsequent tests. RESULTS: Authenticity of the first digital test was not rated higher than the PTs. Test characteristics and environmental conditions, such as image manipulation options and ambient lighting, were optimized based on participants' comments. After adjustments in the third digital test, participants favored the image quality and clinical correspondence of the digital image questions over paper-based image questions. CONCLUSIONS: Digital simulations can increase authenticity of diagnostic radiology assessments compared with paper-based testing. However, authenticity does not necessarily increase with higher fidelity. It can be challenging to simulate the image interpretation task of clinical practice in a large-scale assessment setting, because of technological limitations. Optimizing image manipulation options, the level of ambient light, time limits, and question types can help improve authenticity of simulation-based radiology assessments.

Three distinct types of terminal oxidases participate in the aerobic respiratory pathways of Paracoccus denitrificans. Two alternative genes encoding subunit I of the aa3-type cytochrome c oxidase have been isolated before, namely ctaDI and ctaDII. Each of these genes can be expressed separately to complement a double mutant (delta ctaDI, delta ctaDII), indicating that they are isoforms of subunit I of the aa3-type oxidase. The genomic locus of a quinol oxidase has been isolated: cyoABC. This protohaem-containing oxidase, called cytochrome bb3, is the only quinol oxidase expressed under the conditions used. In a triple oxidase mutant (delta ctaDI, delta ctaDII, cyoB::KmR) an alternative cytochrome c oxidase has been characterized; this cbb3-type oxidase has been partially purified. Both cytochrome aa3 and cytochrome bb3 are redox-driven proton pumps. The proton-pumping capacity of cytochrome cbb3 has been analysed; arguments for and against the active transport of protons by this novel oxidase complex are discussed.