Table 3 Outcomes

 Primary

Total antibiotic exposure, defined as the total number of antibiotic-days by Day 30 ^a

A combined endpoint of adverse outcomes that could be attributable to withholding antibiotics in LRTI, that occur by study Day 30 ^b:

 i. death

 ii. septic shock (vasopressor use for >1 h)

 iii. Mechanical ventilation (via endotracheal tube)

 iv. renal failure (KDIGO, stage 3) [50]

 v. lung abscess/empyema

 vi. development of pneumonia in non-pneumonia LRTI

 vii. Subsequent hospitalization

 Secondary

Antibiotic initiation by the initial ED clinician

Hospital length of stay

90d and 1 year mortality

Intensive care unit admission

Subsequent ED visits

Quality of life (Airway Questionnaire 20) [57]

 Data quality methods

Standardized data collection and recording

Web-based DCF with built-in logic checks, automatic data queries, and streamlined user interface

Periodic DCF checks to monitor data irregularities and protocol compliance

Study coordinator DCF training and periodic conference calls

Center monitoring visits and review of source documents