Any hint of yellow or green color (pus) suggests an airway infection (but does not indicate the type of organism causing it).

More than 25 squamous epithelial cells at low power magnification exam under the microscope strongly suggest salivary contamination.

Specifically, this work has demonstrated that a subgroup of severe asthma patients has airway inflammation that is resistant to treatment with corticosteroids.

[citation needed] Microbiological sputum samples are used to look for infections, such as Moraxella catarrhalis, Mycobacterium tuberculosis, Streptococcus pneumoniae, and Haemophilus influenzae.

Purulent sputum[5] contains pus, composed of white blood cells, cellular debris, dead tissue, serous fluid, and viscous liquid (mucus).