Detection of Novel Influenza A (H1N1) Virus by Laboratory Testing
On April 30, 2009, CDC issued interim guidance on specimen collection and processing [http://www.cdc.gov/h1n1flu/specimencollection.htm], and on May 1, 2009, CDC issued interim guidance on testing for the novel influenza A (H1N1) virus in regions with few or no reported cases [http://www.cdc.gov/h1n1flu/screening.htm]. These documents provide interim guidance to health care providers and clinical laboratories on specimen collection and testing specimens from patients suspected of being infected with novel influenza A (H1N1) virus. Clinicians and laboratories should refer to these interim guidances frequently for updated information.
Additional information for laboratories: At this time the novel influenza A (H1N1) virus is not known to differ in the nucleoprotein antigen that is conserved across all influenza A subtypes. The majority of tests that are currently cleared for detection or differentiation of Influenza A virus in human specimens may be able detect the Type A marker in all influenza A viruses including the novel H1N1 strain. None of the cleared tests, however, are able to distinguish the novel influenza A (H1N1) virus from other influenza A viruses (i.e., to specifically identify novel influenza A (H1N1) virus). The majority of the currently cleared tests have unknown sensitivity and specificity to detect human infection with influenza A (H1N1) virus in clinical specimens.
Most importantly, no influenza tests are sufficiently sensitive to rule out an influenza infection, and clinicians must consider clinical and epidemiological criteria along with laboratory testing results. Clinicians who suspect novel influenza A (H1N1) virus infections in humans should obtain nasopharyngeal swabs, nasal swabs, throat swabs, dual NPS/TS swab specimens and/or nasal aspirates, store the specimen following the testing laboratory’s recommendation (usually under refrigeration), and then contact their state or local health department to facilitate transport and timely diagnosis at public health and other qualified laboratories.
Laboratorians should also maintain awareness of unusual findings and report inaccurate testing results or other problems to the device manufacturer and/or FDA. Health care professionals and consumers may report serious adverse events, such as inaccurate results, or product quality problems with the use of influenza detection assays to the FDA's MedWatch Adverse Event Reporting program either online, by regular mail, fax or phone.
- Online: MedWatch
- Regular Mail: use postage-paid FDA form 3500 and mail to MedWatch, 5600 Fishers Lane, Rockville, MD 20852-9787
- Fax: (800) FDA-0178
- Phone: (800) FDA-1088