Hypothetical cohort of 100 ED patients assessed for traumatic pneumothorax.
tp: true positive – test is positive (indicates pneumothorax) and patient has pneumothorax;
fp: false positive – test is positive (indicates pneumothorax) but patient does not have pneumothorax
tn: true negative – test is negative (indicates pneumothorax not present) and patient does not have pneumothorax;
fn: false negative – test is negative (indicates pneumothorax not present) but patient has pneumothorax