Etiology	Historical findings	Physical examination findings	Confirmatory test or procedure
Serratia marcescens (gram-negative bacterium that produces a red pigment that may be mistaken for blood)	Previous hospitalization, use of broad-spectrum antibiotics, mechanical ventilation	Normal	No red blood cells in sputum; positive culture
Upper gastrointestinal tract source	Coffee ground appearance (not bubbly or frothy), darker blood, nausea, vomiting, gastrointestinal disease	Epigastric tenderness, signs of chronic liver disease (e.g., palmar erythema, spider angiomas, ascites, peripheral edema)	Acidic blood pH, blood mixed with food particles, blood in nasogastric aspiration, esophagogastro-duodenoscopy, barium swallow
Upper respiratory tract source	Bleeding gums, epistaxis, little or no cough	Gingivitis; telangiectasias; ulceration; varices of the tongue, nose, nasopharynx, oropharynx, or hypopharynx	Nasopharyngoscopy if etiology is not apparent