Why, when and how to perform an NPA.

Why test?

An NPA specimen allows rapid testing for seven viruses simultaneously. These are

• respiratory syncytial virus (RSV) adenovirus,
• Influenza A & B,
• parainfluenza 1, 2 & 3
• rhinovirus.

There are several good reasons why it is important to know the causal agent in a case of URTI/LRTI admitted to the hospital:

Bed placement

Patients with the same germ can be placed in the same room/bay. This is especially important when hospital bed spaces are limited as happens during winter when there is a high prevalence of viral infections affecting the lungs.

Accurate diagnosis

Knowing the cause of the infection is helpful for several reasons:            

• A more complete diagnosis - knowing which germ has caused your child's illness.
• Epidemiological monitoring - being aware of which germs are circulating in the community.
• Antiviral drug therapy may be appropriate (e.g. influenza, RSV).

When should testing be done?

The earlier in the course of the infection the more likely a positive result will be found.

Within days of onset of symptoms of URTI/LRTI the amount of virus in nasal secretions tapers off. We encourage collection of specimens at the time of admission (e.g. in the Paediatric Emergency Department).

Delaying collection for any reason reduces the chance of finding the virus.

How to do an NPA

• The catheter (tube) and specimen trap (with tight lid) are set up as in the diagram (see below)
• Consent should be obtained before proceeding.
• Introduction of a suction tube along the floor of the nasal cavity should occur with ease and without discomfort.
• Although it is an invasive procedure, your child should only feel a slightly unpleasant tickly sensation.
• The expected distance the tube is passed in is similar to the distance from the top lip to the ear canal. The tube should be introduced until it stops at the back of the throat.
• Suction is applied and mucus is collected as the tube is slowly withdrawn.
• The mucus is rinsed out by sucking through fluid which collects in the specimen trap. A lid is firmly secured and the NPA is sent to the laboratories.

Central Specimen Collection staff, Nursing staff in Paediatric Emergency and the 4th Floor medical ward are trained to perform NPAs.

Prepared by the Infection Control Team, Women's & Children's Hospital. July 2002

Back to Virology

^TOP	FEEDBACK | SITE INDEX | DISCLAIMER | CONTACT | COPYRIGHT | PRIVACY Printer-friendly version Last Modified: 27-07-2004 14:22:28