Sputa

Sputa, often referred to as sputum, is mucus and other material coughed up from the lower respiratory tract. It is distinct from saliva, though it may mix with oral secretions during expectoration. Sputa is produced by goblet cells and submucosal glands and typically contains mucus, shed epithelial cells, inflammatory cells, and microorganisms present in the airways.

Its appearance varies: clear or white if inflammation is minimal; yellow to green when neutrophils are abundant; brown, rust, or dark colors can reflect blood or inhaled pigments. Pink, frothy sputum can occur in pulmonary edema. Physical characteristics help guide assessment but are not diagnostic on their own.

Laboratory analysis of sputa supports diagnosis of infections and other lung conditions. Gram staining and culture identify bacterial pathogens; acid-fast staining and culture or molecular tests (such as NAAT) aid in detecting Mycobacterium tuberculosis and other mycobacteria. Sputum cytology may be used to detect malignant cells. Induced sputum collection can be used when spontaneous sputum is not available, particularly in suspected tuberculosis or in patients unable to expectorate.

Collection and handling: an early-morning specimen collected after a deep cough is often preferred, with care taken to minimize contamination by oral saliva. Typical volumes are 5–10 mL or more for testing; multiple consecutive morning samples may be requested for specific conditions like tuberculosis. Proper infection control and biosafety practices are important because sputa can contain infectious agents. Contamination with oral flora can complicate interpretation, sometimes necessitating repeat samples or alternative specimens.