Table 1.

Advantages and limitations of mucus and mucin collection methods

Method	Advantages	Limitations
Cell culture wash	- Requires minimal specialized equipment and is not overly tedious. - Can sample mucus in response to interventions [63, 64]. - Potential for repeated collection and/or longitudinal study.	- Accumulated mucins might not be removed properly if washing is not done successively or is incomplete [65]. - Samples may require pooling [66].
Bronchoalveolar lavage	- Allows for direct sampling of the airway fluid - Applicable in vivo [67] and ex vivo [68]. - Relatively large volumes can be retrieved. - Materials to perform are standard. - Can be performed in human patients [69]. - Potential for repeated and/or longitudinal sampling.	- Must be clinically indicated in order to perform in humans. - Generally done under local anesthesia in vivo [70]. - Fluid retrieved is a combination of multiple cells and multiple proteins [67]. - Volume recovered is variable [71]. - Non-adherent proteins may be overrepresented
Sputum (spontaneous and induced)	- Provides information about mucus and mucins in the lower airways - Spontaneous sputum requires no intervention for its production - Induced sputum provides a higher proportion of viable cells [72]. - Guidelines in place for inducing sputum in human [73].	- Potential for contaminated with saliva. - Induced sputum usually requires inhalation of hypertonic saline, which can be irritating and change composition of mucus [74, 75]. - Success of sputum induction influenced by inflammation [72]. - Variations in the amount of sputum produced [76]. - Not really applicable to animal models.
Bronchoscopy	- Direct sampling of mucus when used to remove plugs [77]. - Provides significant diagnostic information. - Can be performed in human and animal patients.	- Performance in human patients or animal patients requires highly specialized equipment and training - Typically performed under conscious sedation, occasionally occur under general anesthesia [70].
Endotracheal tube sampling	- Direct sampling of mucus [78, 79].	- Hydration of the mucus varies from the inside or the outside of the tube [80] - Endotracheal tube placement in human and animal patients requires highly specialized training and a licensed medical practitioner.