Influenza Virus Type A and Type B, Molecular Detection, PCR
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Influenza is usually a mild illness of the upper respiratory tract resulting in malaise and headache, followed by abrupt onset of fever, severe myalgia, and usually a nonproductive cough. Influenza virus infection can lead to more serious complications such as:
-Combined influenza and bacterial pneumonia
-Primary influenza virus pneumonia
-Severe complications in patients with pre-existing conditions such as rheumatic heart disease, bronchopulmonary disease, impaired renal function, and immunocompromised patients
-Serious illness during the first 2 years of life, with croup, bronchitis, and pneumonia
Type A viruses are typically associated with the most serious influenza epidemics, while type B viruses typically cause milder infections than type A.
The prevalence of influenza varies from year to year, with outbreaks typically occurring during the fall and winter months.
Rapid detection of influenza virus types A and B in upper respiratory tract specimens.
Positive results are diagnostic of influenza A or influenza B.
Negative results do not rule out infection with influenza virus.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Results will vary depending on socioeconomic status, age of population, geographic location, time of year, and specimen collection/handling.
The sensitivity of the assay is very dependent upon the quality of the specimen submitted.
The test is specific for influenza A and B; therefore, the results do not eliminate the possibility of infection with other respiratory viruses.
A negative test does not exclude infection with influenza A or influenza B virus. Therefore, the results obtained should be used in conjunction with clinical findings to make an accurate diagnosis.
This assay detects both viable and non-viable virus. Test performance depends on viral load in the specimen and may not correlate with cell culture performed on the same specimen.
Performance of the assay has not been established for monitoring antiviral treatment of influenza.
Use of transport media will result in dilution of samples, which may lower overall test sensitivity.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Negative for influenza A nucleic acid
If positive, reported as influenza A nucleic acid detected
Negative for influenza B nucleic acid
If positive, reported as influenza B nucleic acid detected
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Pachucki CT: The diagnosis of influenza. Semin Resp Infect 1992;7:46-53
2. Wendt CH: Community respiratory viruses: organ transplant recipients. Am J Med 1997;102:31-36; 42-43