246 Chapter 10 microbiological data available after 28 days of follow-up [10]. A definite diagnosis of CAP was defined as an acute infection of the respiratory tract (criteria defined above) and a parenchymal lung consolidation on ULDCT or CXR, and was based on consensus by an adjudication committee using a diagnostic handbook we developed for standardised and reproducible categorisation of diagnoses [10]. In an exploratory analysis we used a broader definition of suspected CAP, by also including patients with a temperature between 36°C and 38°C. Outcome measures were number of patients admitted to the hospital, total antibiotic use over 28 days, length of hospital stay, mortality, and functional health at day 28 after ED presentation represented by the short form (SF)-12 questionnaire score. Results In the OPTIMACT trial 2418 patients with non-traumatic pulmonary disease were included. Of those, 492 patients were clinically suspected of having CAP and were included in the current analysis (mean age 58 (SD ± 19) years; 53% male). 261 patients were allocated to ULDCT and 231 to CXR for radiological examination. Baseline characteristics were comparable between groups (Table 1). After imaging, 78 of the 261 clinically suspected CAP patients in the ULDCT group were discharged from the ED with the diagnosis CAP (31%), as compared to 75 out of 231 (34%) in the CXR group (P = 0.6; chi-square test). After evaluation of all available data after 28 days of follow-up, in the ULDCT group 88 of the 261 clinically suspected CAP patients were diagnosed with definite CAP (35%), as compared to 75 out of 231 (34%) in the CXR group (P = 0.8; chi-square test). Differences between groups in hospital admission, length of hospital stay, mortality, proportion of patients treated with antibiotics, median number of days of antibiotic treatment (days on therapy) and functional health at day 28 were not detected (Table 1; P-values not significant). In the OPTIMACT trial, we reported a higher number of patients with CAP in the ULDCT group, both at ED discharge and after 28 days of follow-up (definite CAP)[7]. To explain this discrepancy with the current analysis, we hypothesized that the higher diagnostic accuracy of ULDCT over CXR is mainly relevant in a subset of patients with CAP, such as patients with incipient CAP or an atypical clinical presentation of CAP. In an exploratory analysis we therefore selected patients with signs or symptoms of an acute lower respiratory tract infection (as defined above), but a temperature between 36°C and 38°C. This resulted in 1262 patients, of which 608 patients were allocated to the ULDCT group and 654 patients to the CXR group. Of the 1262 patients selected by these exploratory criteria, 106 of 608 patients in the ULDCT group were discharged from the ED with CAP (18%), as compared to 71 of 654 (12%) in the CXR group (P = 0.001; chi-square test). After evaluation of all available data at day 28, in the ULDCT group 105 of 608 patients were diagnosed with definite CAP (18%), as compared to 70 of 654 (11%) in the CXR group (P = 0.001; chi-square test).
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