This is a randomized study that sought to compare the rule-out capacity and antibiotics prescriptions associated with two different diagnostic imaging strategies (ultra-low-dose chest computed tomography versus chest radiography) in a group of healthy adults presenting to the emergency department (ED) with suspected community-acquired pneumonia (CAP).

Between October 2017 and December 2018, we prospectively enrolled consecutive adult patients with suspected community-acquired pneumonia based on at least one respiratory symptom and focal auscultatory findings and at least one sign related to infection, for whom no definitive diagnosis was possible by clinical judgment.

Eligible patients were randomly assigned to their imaging evaluation in a 1:1 ratio to either ultra-low-dose chest computed tomography (ULDCT) or the standard evaluation strategy using conventional chest radiography (CR).

This study sought to compare the rule-out capacity and antibiotics prescriptions associated with those two different diagnostic imaging strategies (ULDCT versus CR) in a group of healthy adult patients presenting to the ED with suspected CAP.

Inclusion Criteria:

• Suspected CAP;
• At least one respiratory symptom (new or increasing cough, expectoration, dyspnea or chest pain) and
• At least one symptom related to infection (fever ≥ 38°C, chills, sweating, myalgia, mental confusion or headache) and
• Focal auscultatory findings during physical examinations (crackling rales)
• No definitive diagnosis possible by clinical judgment.

Exclusion Criteria:

• Score in at least one clinical part of the CURB-65 or PSA scores
• Clinical diagnosis of rhinosinusitis and acute nasopharyngitis and who had already been treated with antimicrobial therapy for this episode of disease
• pregnancy;
• the presence of other respiratory diseases such as chronic obstructive pulmonary disease (COPD), asthma, interstitial lung disease, chronic diseases or other chronic airway conditions;
• diagnosis of congestive heart failure;
• body mass index (BMI) greater than 30;
• inability to hold the breath for at least 10 seconds

A total of 211 patients were included from the 237 eligible ones. Sixteen patients refused to sign the informed consent form and five were excluded due to technical errors during image acquisition. Two patients exhibited BMIs higher than 35 and did not fulfil the inclusion criteria; three patients could not be reached for follow-up.

Among the 211 patients included, 98 (46.45%) were imaged by CR and 113 (53.55%) by ULDCT. There were no significant differences among patients in the CR and ULDCT groups concerning age, gender, height, weight, and BMI.

there is no plan to make individual participant data (IPD) available to other researchers.