esputum

Esputum, more commonly written sputum, is a viscid mixture of mucus and saliva expelled from the lower airway up through the mouth. It is produced by goblet cells and submucosal glands lining the respiratory tract and is influenced by inflammatory and infectious processes. Sputum production increases in many respiratory conditions and can be collected for analysis.

Chemically, sputum contains mucus, cellular debris, inflammatory cells (such as neutrophils and macrophages), bacteria or fungi, viruses, and occasionally blood. Gross appearance varies by condition: mucoid white; purulent yellow-green in bacterial infection; blood-tinged or rust-colored in hemorrhagic processes or pulmonary infarction.

Collection and quality: Ideally collected by deep cough into a sterile container after rinsing mouth; saliva contamination reduces quality. Induced sputum may be collected using inhaled hypertonic saline for patients unable to expectorate; early morning samples are often preferred. For suspected tuberculosis, multiple early morning specimens on consecutive days are recommended.

Laboratory analysis includes gross examination, Gram stain, culture, acid-fast bacilli staining, fungal stains, and molecular tests (PCR). Sputum cytology can detect malignant cells. The results guide diagnosis and antibiotic selection; repeated sputum sampling may be needed to monitor disease or confirm clearance.

Handling: Store at 4°C if delayed; process promptly; use biosafety precautions for infectious specimens.