Lab testing for H1N1

H1N1 Influenza 09 is a strain of Influenza A. A positive Influenza A test will not differentiate it from normal seasonal Influenza A. Subtyping is required and this is performed at the public health reference laboratory in Brisbane.

Case definition

A suspected case is a person with an acute respiratory illness with onset:

Within 7 days of close contact with a person who is either a confirmed case of H1N1 Influenza 09 (human swine influenza) virus infection or a suspected case with a Influenza A positive test result.
Within 7 days of travel especially to Mexico, USA, Canada, Japan, Panama and the state of Victoria.

Please note that this definition is subject to change as the situation evolves.

Collection room instructions

Triage patients with respiratory symptoms so that they are moved through the collection/waiting rooms as quickly as possible.
Waiting patients should be offered surgical masks (or N95 masks where these are not available), alcohol hand rub and tissues. Disinfect any potentially contaminated surfaces with 70% alcohol.
Apply respiratory precautions during the collection and wear personal protective equipment (PPE). The collector is to wear gloves, a gown, goggles and N95 mask (fit tested for size) for those patients who fulfil the case definition for possible swine flu. For those patients who do not fulfil the case definition, it is sufficient for the collector to wear an ordinary surgical mask.
A nasopharyngeal swab (NPS—orange top) is the preferred specimen but if this swab type is not available a throat swab (TS—green top) can be collected. Trials have demonstrated equal sensitivity for recovery of Influenza from both well collected NPS and TS.
Nasopharyngeal aspirates (NPA) must not be performed.
After collection label the specimens and transport at room temperature.
Clean the environment thoroughly after the procedure using 70% alcohol.
Remove and dispose of PPE carefully after the procedure (remove gloves, wash hands or use alcohol based rub).
Urgent specimens can be tested for the presence of Influenza A using a rapid test. Please send 2 swabs if this is requested. While the sensitivity of these rapid tests is unknown it is only likely to be of the order of 60 -70%. Positive results for this test indicates the presence of Influenza A. Further testing is required to determine the subtype.

Multiple swabs collected will be combined for PCR testing unless a rapid test is required.

Swab collection

Use a flock swab (orange top) for Nasopharyngeal swabs (NPS) or a viral swab (green top) for throat swabs (TS). These two types of swabs do not have any media contained in their sheath which makes it suitable for PCR testing.

Nasopharyngeal swab (NPS)

Measure the distance from the patient’s nostril to the earlobe, using an orange to flocked swab.
Arrange for the patient to sit or lie down with the head tilted backwards. If the procedure is being performed on a child ensure someone holds the child’s forehead firmly in the position as well as secures the arms folded across their abdomen.
Stand on either the left or right side of the patient.
Ask the patient to breathe through their mouth throughout the procedure if possible. This may help to alleviate any gagging sensation.
Guide the swab gently through the anterior nostril and pass horizontally along the floor of the nasal cavity. The depth of insertion should be at least half the measured distance from the earlobe to the anterior nostril. Gently but quickly rotate the swab whilst withdrawing it.
Using the same swab repeat the process on the other nostril. Sampling both nostrils increases the yield of material to be tested.

Throat swab (TS)

Sample the throat using a flocked swab or the viral swab.

Turnaround times

Respiratory virus testing is batch tested. Results for specimens for Swine Flu, received by 8.00 am will be available on the same day. Specimens collected after that time will be tested on the next available PCR run and results may be available later that day or early the following day.