New research data shows that influenza antigen testing correlates best with the infectivity period

A recent study by Inagaki et al. in The Journal of Infectious Diseases shows that, compared to PCR or culture, influenza antigen testing correlates best with the infectivity period.

The researchers studied how long influenza is infective and which of the commonly used methods – culture, PCR and antigen testing – correlates best with the infectivity of the disease. Inagaki et al. used ferrets as a model species to study the infectivity.

The results indicate that the influenza was transmissible until day 5 after inoculation. This corresponded to high culture titers and positive results in antigen testing. Detection of influenza A by PCR instead did not show any correlation to the cessation of transmission of the disease, but it returned positive results until 11–13 days after inoculation. The authors concluded as follows:

• The antigen-detection test predicted the infectious period with comparable if not better accuracy with culture.
• The PCR-based detection of viral RNA load failed to correspond to the end of infectious period.
• The infectious period is grossly overestimated when PCR is used to assess infectivity. Thus, culture and antigen-detection testing are far more informative than PCR for identifying the cessation of contagion.

The results of Inagaki et al. agree well with previous mariPOC® studies done for human bocavirus (New Microbes New Infect. 2016 11:17–19.), coronavirus (manuscript submitted), RSV and influenza A virus (unpublished ArcDia data), which indicates that the viral load of infected patients swiftly decreases on day 5–6 after the on-set of symptoms.

Source: Inagaki K, et al. The Journal of Infectious Diseases. 2016;213(3):407–410.

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