New tests aim to cut unnecessary antibiotics for lung infections in hospitals

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: Stage 1: * Age ≥ 18 years * Suspected HAP\* For the purposes of this study, HAP is defined as per the BTS and FDA definitions i.e. pneumonia which develops 48 hours after an admission to hospital for an alternative diagnosis; or a new presentation to hospital with pneumonia in a patient who has been discharged from an overnight stay in hospital within the last 10 days. Stage 2: * The clinician intends to treat the patient for HAP or a hospital acquired respiratory tract infection (RTI). * A sputum sample has been obtained before 2nd dose of antibiotic. Exclusion Criteria: Stage 1: * Already received a chest X-ray to confirm suspected HAP diagnosis * Diagnosis or suspected diagnosis of ventilator acquired pneumonia * Intention to palliate rather than cure * Interventions cannot be completed before administration of second antibiotic dose\* * Cannot be randomised to low-dose, non-contrast CT scan on clinical grounds e.g. strong suspicion of PE\*\* * Pregnancy\*\*\* * Previous study participation (patients with second of third episodes of HAP will not be re-recruited) In the circumstance where a patient is diagnosed with HAP whist receiving antibiotics for a non-respiratory infection e.g. cellulitis or UTI, if the HAP diagnosis leads to a change in the antibiotic prescription to cover the HAP then that patient will be eligible for recruitment. However, if the diagnosis of HAP does not result in a change in antibiotic then the patient is not eligible. A non-contrast, low-dose thoracic CT scan is an inappropriate test for a PE and if that is high in the differential diagnosis then tick yes here. A urine pregnancy test is required as part of routine care prior to a chest X-ray or CT scan. If the test reveals the patient is pregnant, they will not be eligible for the study as they will be unable to receive a CT scan as part of this study. Pregnancy tests are not required at future time points. Stage 2: \- Following the CXR or CT the clinician decides not to treat with antibiotics for either HAP or a hospital acquired RTI.