Rapid testing
Point of care rapid tests capable of detecting influenza A and B virus infections are available,but healthcare providers and public health personnel should be aware that rapid influenza diagnostic tests have limited sensitivity and false negative results are common. Thus, negative results from rapid influenza diagnostic tests should not be used to guide treatment decisions. In addition, false positive tests can occur and are more likely when influenza is rare in the community. When laboratory confirmation is desired, the preferred tests are polymerase chain reaction (PCR) and/or viral culture.
DPH discontinued the use of the Rapid Influenza Diagnostic Report Form and no longer requires reporting of rapid flu tests.
Polymerase Chain Reaction (PCR) and Viral Culture Testing
Laboratories in Massachusetts report all positive influenza tests they perform to the Massachusetts Department of Public Health (DPH), including PCR and viral culture tests.
Variant flu
When an influenza virus that normally infects animals (such as pigs, dairy cattle or birds) is found in people, it is called a variant influenza virus and is designated with the letter “v” after the subtype.
- In recent years, human infections with A(H1N1)v, A(H1N2)v, A(H3N2)v, A(H5N1), and most recently A (H5N5) viruses have been detected in the United States (see CDC’s Risk Assessment and Reporting of Variant Influenza Viruses and FluView
Most human infections with variant viruses have occurred in people exposed to infected dairy cattle, poultry, pigs (e.g. children exposed to pigs at a fair or workers in the swine or dairy industry), but there have been rare instances of person-to-person spread of variant viruses.
Variant strain testing
If a clinician suspects a variant strain of influenza, a specimen should be submitted promptly to the MA SPHL using the Respiratory Surveillance Specimen Submission Form. (To process this request please call (617) 983-6800.)
Testing at the State Public Health Laboratory
In addition to variant strain testing and as part of a more comprehensive respiratory surveillance initiative, MA SPHL performs testing on submitted samples from volunteer surveillance sites (ILINet) to confirm typing and subtyping of circulating influenza viruses. If negative for influenza, testing for evidence of adenovirus, respiratory syncytial virus (RSV), parainfluenza virus (PIV) types 1-4, SARS-CoV-2, coronavirus (HCoV) HKU1, OC43, NL63, 229E, human metapneumovirus (HMPV), rhinovirus/enterovirus (RHV/ENT), Bordetella parapertussis, Bordetella pertussis, Chlamydia pneumoniae, and Mycoplasma pneumoniae using a multiplex PCR respiratory panel will occur.
Specimen collection and shipping to MA SPHL
Flu specimens should be collected as soon as possible after onset of illness, preferably within three days (72 hours) and submitted immediately to MA SPHL the same day. Specimens collected >5 days from symptom onset are unsuitable for testing. If shipped to MA SPHL ≥3 days from collection or on a Friday, specimen(s) must be frozen at <-20°C and shipped frozen with dry ice the following week. Specimen temperature upon receipt is critical for testing acceptance. Specimen Collection for Respiratory Virus Testing Instructions.
Find State Public Health Laboratory specimen submission forms in the downloads section of the Influenza information for healthcare and public health professionals handbook.