Tjitske van Engelen

299 General discussion Short-term functional health was comparable between ultra-low-dose chest CT and chest X-ray patients, as were hospital admissions, length of hospital stay and mortality rates. These results do not support routine use of ultra-low-dose chest CT in the work-up of patients suspected of non-traumatic pulmonary disease at the emergency department. The study population and infrastructure of the OPTIMACT study were well-suited for additional research into the value of ultra-low-dose chest CT in patients suspected of pneumonia in the emergency department. In Chapter 10 we focused on these patients, but despite the earlier reported higher sensitivity of ultra-low-dose chest CT to detect community-acquired pneumonia, the number of patients with a community-acquired pneumonia diagnosis, at discharge from the ED as well as after reviewing all available clinical data at day 28, was not significantly different between the ultra-low-dose chest CT and chest X-ray groups. This was reflected by the absence of differences in management (hospital admission, proportion of patients treated with antibiotics, median number of days of antibiotic treatment), or outcomes (length of hospital stay, mortality, functional health at day 28) between both patient groups. However, in an exploratory analysis, in the large subgroup of patients with signs or symptoms of an acute lower respiratory tract infection but a temperature between 36°C and 38°C, significantly more patients in the ultra-low-dose chest CT group were discharged from the ED with community-acquired pneumonia (106/608, 18%) compared with the chest X-ray group (71/654, 12%, P = .001; χ 2 test), and this difference was still present at day 28. This suggests that the value of ultra-low-dose chest CT seems most pronounced among those patients whose clinical presentation is not straightforward, such as patients who are elderly or afebrile. Interestingly, in another substudy of the OPTIMACT trial, we showed that pulmonary imaging in patients with suspected infection but no respiratory symptoms or signs could detect clinically significant pneumonia, and the sensitivity of ultra-low-dose chest CT to detect this was significantly higher than that of chest X-ray [22]. This also suggested that the increased sensitivity of ultra-low-dose chest CT compared to chest X-ray is mainly of added value in vulnerable and immunocompromised patients. Future studies should focus on identification of those patients at the ED who benefit from the increased sensitivity of ultra-low-dose chest CT and in whom ultra-low-dose chest CT should be the preferred imaging method. 12

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