Study procedures
pneumonia, neutropenic, HCAP, human immunodeficiency virus (HIV) infection, healthcare-associated pneumonia
PNEUMONIA, ASPIRATION PNEUMONIA, BRONCHOPNEUMONIA, HEMATOLOGICAL MALIGNANCY
History taking, physical examination, and laboratory tests were initiated by the attending physician. After setting the indication for chest imaging and acquiring informed consent, the attending physician provided a clinical question on the structured and standardized radiology request form. This was followed by either ULDCT or CXR, according to the imaging method allocated to the month of presentation. If the clinical question was not adequately answered after obtaining the CXR or ULDCT, standard additional imaging (e.g., chest CT with intravenous contrast medium, CT pulmonary angiography) was performed. The median ULDCT dose was 0.2 mSv (IQR 0.2 to 0.3 mSv). The median CXR dose for portable anterior–posterior (AP) CXR was 0.02 mSv (IQR 0.02 to 0.03 mSv) and for bucky CXR posterior-anterior (PA) and lateral 0.05 mSv (IQR 0.03 to 0.07 mSv). Additional technical information on the imaging techniques used (ULDCT and CXR) is available in the Radiologists used a structured standardized report to optimize and standardize reading. Reading and reporting were performed or supervised by the radiologist on call at the time of clinical management, also outside office hours. The ULDCT and CXR were read with prior imaging if available. To increase inter-reader consistency, the residents and radiologists less experienced in the field of chest imaging were supervised by a group of seven radiologists with a subspecialty in chest imaging. When a radiologic diagnosis of pneumonia was made, a pneumonia pattern was reported: lobar, interstitial, or bronchopneumonia. Further details regarding the design of the OPTIMACT trial and the main outcomes are reported elsewhere [The data collected at baseline consisted of medical history, physical examination results, laboratory values, microbiological and radiological evaluation, and clinical diagnosis at ED discharge. Participants were followed for 28 days. All clinical, radiological, and microbiological data from participants available after 28 days of follow-up were reviewed post hoc. Based on these findings, a final day-28 diagnosis was assigned. A diagnostic handbook was developed to establish 32 possible day-28 diagnoses, including CAP, healthcare-associated pneumonia (HCAP), and aspiration pneumonia. Details of this handbook and its validation have been reported elsewhere [Patients were categorized as immunocompromised if they had a history of human immunodeficiency virus (HIV) infection, organ or bone marrow transplantation, or hematological malignancy, had received recent chemotherapy (i.e., within the previous six months), were neutropenic, or if they used immunosuppressive medication (e.g., steroids or disease-modifying anti-rheumatic drugs (DMARDS).