A nasal drainage test may be done if your health professional thinks your child's respiratory infection is caused by respiratory syncytial virus (RSV). Nasal drainage tests help determine what precautions, such as isolation procedures, are needed to prevent the spread of infection. A sample of nasal drainage may be collected for testing by:

• Nasal washing. A small amount of salt water (saline) is put into the nose while the child is lying down. A syringe is used to remove the water and a sample of nasal drainage from the nose.
• Nasal swab. A cotton swab is inserted into the nose. The inside walls of the nose are swabbed to collect mucus and pieces of cell waste. The swab may be left in the nose for up to 3 minutes to get a good sample. Both sides of the nose are usually swabbed.

Nasal washing is preferred to nasal swabbing because it is more accurate.