Indications for Testing
RSV is usually diagnosed based on clinical presentation and patient history; however, the following populations warrant laboratory testing during RSV season if they present with severe respiratory illness:
- Young children (especially infants younger than 6 months of age)
- Adults 65 years or older
- Those with underlying heart and lung diseases (eg, congestive heart failure, chronic obstructive pulmonary disease)
Rapid Antigen Detection Tests
RADTs are popular for RSV testing due to their ease of use, quick turnaround time, and acceptable sensitivity and specificity in infants and young children. Some RADTs (eg, BinaxNOW RSV) can be used at the point of care in outpatient settings and require nasopharyngeal swabs or aspirates. However, false-negative results are possible, and clinicians may consider retesting by a more sensitive method (eg, PCR) if the result might influence patient management.
Direct Fluorescent Antibody
Direct fluorescent antibody (DFA) testing is a fairly reliable methodology for use in infants and young children; however, sensitivity in adults and older children is poor due to a lower rate of viral shedding compared to that in younger children. Because DFA is more cost-effective than molecular testing (eg, PCR), it is preferred for infants and young children. The sensitivity of DFA testing depends on an adequate specimen (nasopharyngeal swab or aspirate).
Polymerase Chain Reaction
Molecular testing (eg, PCR) can detect RSV as well as other respiratory viruses in nasopharyngeal swabs and aspirates with high sensitivity and specificity. Molecular testing is particularly useful in older children and adults and is preferred for hospitalized and immunocompromised patients. PCR is more sensitive than either antigen testing or viral culture. Because of its high sensitivity, it may detect RSV in a patient after the infection has resolved, so a positive result should be clinically correlated with the patient’s symptoms. Additionally, PCR is more expensive than DFA, and the turnaround time may be longer in certain laboratory settings.
Culture is not recommended for initial clinical management due to slow turnaround time. However, culture is still important for detecting coinfections in patients.
Comparison of Testing Methodologies
||Can be performed on site
Rapid turnaround time (<30 min)
Acceptable sensitivity and specificity in young children
|Not recommended for adults and older children due to lower sensitivity/specificity
False-negative results are possible
||Recommended for infants and children due to high sensitivity in this patient population
Shorter turnaround time than viral culture or PCR
|Lower sensitivity than PCR; not useful for adults and older children
Adequate specimen influences sensitivity of the assay
||Very high sensitivity and specificity
Can detect other respiratory viruses
Low likelihood of false-positive or false-negative result
Detects viral RNA for longer duration than other RSV tests
Detects virus in adults and older children, despite their lower rate of viral shedding compared to younger children
|More expensive than DFA
Longer turnaround time than DFA
May detect virus after the infection has been cleared
Virus can be stored for diagnostic studies
|Long turnaround time (3-5 days)
|Sources: Henrickson ; Chartrand