Discussion
comorbidity, pneumonia, cardiovascular and pulmonary comorbidities, fever, non-traumatic thoracic, hematologic malignancies, consolidations, cardiovascular or pulmonary comorbidities
DISEASE, PNEUMONIA, HEMATOLOGIC MALIGNANCIES
In this analysis of the OPTIMACT trial, we observed that pneumonia can occur in patients with fever or elevated CRP even if they do not show respiratory signs or symptoms. In total, 22 patients (10%) were diagnosed with pneumonia. ULDCT had a significantly higher sensitivity in the detection of pneumonia than CXR: 93% versus 50%. The cases of pneumonia we found were clinically significant, most patients required admission and were prescribed antibiotics. According to our findings, clinical characteristics or comorbidities alone cannot be used to identify patients with or without pneumonia, compatible with earlier observations that no single symptom, sign, or comorbidity is predictive of pneumonia [To our knowledge, only one other study has been done to investigate the yield of pulmonary imaging in ED patients who have a fever or elevated CRP without respiratory signs or symptoms [Compared to CXR, ULDCT had a significantly greater sensitivity for detecting pneumonia. A retrospective study in patients presenting with non-traumatic thoracic emergencies at the ED described CXR’s similarly low sensitivity (37.7%) for pneumonic consolidations when compared to conventional chest CT [There were remarkably few patients with cardiovascular and pulmonary comorbidities in our group, which is likely due to the inclusion and exclusion criteria used. It is rare for patients afflicted with cardiovascular or pulmonary comorbidities to have no respiratory symptoms or signs [Due to the pragmatic nature of the OPTIMACT trial, concealment of allocation was not possible. This may have influenced the behavior of physicians in including patients in the ULDCT or CXR months and may explain the higher proportion of patients with hematologic malignancies and recent chemotherapy in the ULDCT group. However, in our study group, we did not find a relationship between comorbidities and the presence of pneumonia. Second, due to the nature of this study, patients underwent either ULDCT or CXR, not both. Estimation of sensitivity and specificity was performed based on independent samples, while a more precise comparison would have been made in paired samples (i.e., CXR and ULDCT performed on the same patient). However, that would have prevented the evaluation of patient outcomes per diagnostic arm. Nonetheless, given the sample size, our results provide strong indications that ULDCT outperforms CXR in the detection of pneumonia in patients without respiratory signs or symptoms. The day-28 diagnosis was used as a reference standard, but results of the diagnostic strategy, ULDCT or CXR, were incorporated in the day-28 diagnosis, and this may have influenced the outcome. The influence is probably limited because the follow-up period of 28 days results in a post hoc day-28 diagnosis that uses all clinical, radiological, and microbiological data obtained during follow-up, including additional imaging and the natural course of the disease.Finally, due to the small number of patients who were diagnosed with pneumonia, we had limited power to find patient characteristics that were indicative or predictive of pneumonia in patients without respiratory signs or symptoms.Despite these limitations, this study’s strengths should also be highlighted. It was performed in the EDs of a tertiary and a large regional teaching hospital, where it included the complete spectrum of patients who present at the ED and who, according to the physician, require pulmonary imaging. This means that the results of this study are generalizable to other settings. Furthermore, this study was longitudinal in design, with a follow-up period of 28 days, and therefore the diagnosis of pneumonia could be established considering all clinical, radiological, and microbiological data from participants available after 28 days of follow-up. In this way, the clinical diagnosis of pneumonia could be established much more reliably than would have been possible when only the data from the moment of imaging would have been available.In conclusion, our results imply that pulmonary imaging can at least be considered in patients who have a fever, low core body temperature, or elevated CRP without respiratory symptoms or signs. When the objective is to exclude pneumonia from the differential diagnosis in this patient group, for instance, because the patient is immunosuppressed, ULDCT’s improved sensitivity compared to CXR is a significant advantage.