Respiratory Syncytial Virus (RSV), Molecular Detection, PCR
Rapid and accurate detection of respiratory syncytial virus
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Respiratory syncytial virus (RSV) is a respiratory virus that infects the respiratory system and can cause an influenza-like illness. Most otherwise healthy people recover from RSV infection in 1 to 2 weeks. However, infection can be severe in infants, young children, and older adults. RSV is the most common cause of bronchiolitis (inflammation of the small airways in the lung) and pneumonia in children under 1 year of age in the United States, and is more frequently being recognized as an important cause of respiratory illness in older adults.
RSV RNA can be detected by PCR in respiratory secretions, including upper and lower respiratory specimens. Nasopharyngeal swabs or aspirates are the preferred specimen types for detection of RSV RNA. Nasal swabs have been shown to provide equivalent yield to nasopharyngeal specimens for molecular detection of influenza A and B RNA, but not RSV RNA.(1,2) Tracheal aspirates are generally not acceptable for testing due to the viscous nature of these specimens.
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.
A positive test result indicates that the patient is presumptively infected with respiratory syncytial virus. The test does not indicate the stage of infection. Laboratory test results should always be considered in the context of clinical observations and epidemiologic data in making a final diagnosis.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Given that influenza A and B and respiratory syncytial virus (RSV) can cause identical appearing clinical illness, this test should typically be ordered as a panel that includes both influenza A/B and RSV (PROD/60552 Influenza Virus Type A and Type B, and Respiratory Syncytial Virus (RSV), Molecular Detection, PCR).
This test has been designed to minimize the likelihood of false-positive test results. However, should false-positive results occur, risks to patients could include a recommendation for quarantine of household or other close contacts, a recommendation for patient isolation that might limit contact with family or friends, the ability to work, or the ability to receive certain medical care, prescription of an antiviral drug or other therapy, or other unintended adverse effects.
The sensitivity of the assay is very dependent upon the quality of the specimen submitted. Nasopharyngeal swabs or aspirates are the preferred specimen types and are optimal for detection of RSV RNA. However, the test is validated for use with most upper and lower respiratory specimens, including nasal swabs, throat swabs, bronchoalveolar lavage specimens, and bronchial brushings or washings. Tracheal aspirates are not acceptable for testing due to the viscous nature of these specimens.
This test should not be performed unless the patient meets clinical and epidemiologic criteria for testing.
The test is specific for RSV; therefore, the results do not exclude the possibility of infection with other respiratory viruses. Influenza C virus is not detected by this assay.
Negative results do not preclude infection with RSV and should not be used as the sole basis for treatment or other patient management decisions.
This assay detects both viable and nonviable 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 or duration of infection with RSV and influenza viruses.
All testing was performed on the Roche LightCycler 480 instrument using the Prodesse ProFlu+ test for influenza A, influenza B, and respiratory syncytial virus (RSV).
A total of 113 clinical specimens were tested by this Prodesse ProFlu+ Assay and the BinaxNow RSV antigen card test. Discrepant specimens were tested by a laboratory-developed RSV PCR assay targeting the nucleocapsid gene. Of these, 89 specimens were positive by both methods and 9 were negative by both. A total of 14 specimens were detected by the BinaxNow test that were not detected by the ProFlu+ PCR, but only 7 of these were positive by additional PCR testing (final sensitivity=93%). One specimen was detected by the ProFlu+ PCR and not the BinaxNow test.
-Qualitative intra-assay precision=100%; standard deviation <0.9 PCR cycles
-Qualitative interassay=98%; standard deviation <0.9 PCR cycles
Limit of detection (LoD):
-The LoD using a quantified plasmid standard was 10 targets/microliter for swab respiratory specimens, and 25 targets/microliter for nonswab specimens.
-The LoD using quantitated cells cultures was 10 TCID50/mL for RSV.
No cross-reactivity observed using a panel of 34 viruses, bacteria, fungi, and mycobacteria that may be found in respiratory specimens.
No inhibition was seen in any of the extracted lower or upper respiratory specimens when tested at the LoD.
A review of the literature indicates that the reference range is "negative" for this assay. This assay is designed to detect RSV and is to be used for patients with a clinical history and symptoms consistent with this disease. This test should not be used to screen healthy patients.
This is a qualitative assay and results are reported as negative or positive for RSV.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Meerhoff TJ, Houben ML, Coenjaerts FE, et al: Detection of multiple respiratory pathogens during primary respiratory infection: nasal swab versus nasopharyngeal aspirate using real-time polymerase chain reaction. Eur J Clin Microbiol Infect Dis 2010;29:365-371
2. Heikkinen T, Marttila J, Salmi AA, Ruuskanen O: Nasal swab versus nasopharyngeal aspirate for isolation of respiratory viruses. J Clin Microbiol 2002;40(11):4337-4339