I thought I posted this before but I did not, Pediatrcis 2011, prospective cohort study with 2574 patients under 21 years old. Interestingly, 16 % of patients had radiographic pneumonia.
Patients with chest pain, focal rales, duration of fever, and oximetry levels at triage were significant predictors of pneumonia. Among these hypoxia o2<92% had strongest predictor of pneumonia. their conclusion is history and physical examination findings can be used to risk stratify children for risk of radiographic pneumonia.
You will have benefit if you read the following link: