Rapid diagnostic testing for influenza

Rapid influenza diagnostic tests (RIDTs) are screening tests for influenza virus infection.

Rapid influenza diagnostic tests can provide results within approximately 15 minutes.

RIDTs differ in some important respects.

Some can identify influenza A and B viral antigens and distinguish between them in respiratory specimens, while others cannot distinguish between them in respiratory specimens.

RIDTs vary in terms of sensitivity and specificity when compared with viral culture or RT-PCR.

Sensitivities are generally approximately 50-70%, and specificities are approximately 90-95%.

Specimens for analysis should be collected as close as is possible to the start of symptoms.

Very young children and Immunosuppressed patients may have detectable influenza viruses in respiratory specimens for prolonged periods of weeks to months.

The predictive value of influenza tests depends on the prevalence of the influenza infection.

False-positive and true-negative influenza test results are more likely to occur when disease prevalence is low.

The prevalence of influenza is generally low at the beginning and end of the influenza season.

Conversely, false-negative and true-positive influenza test results are more likely to occur when disease prevalence is high, which is typically at the height of the influenza season.

Positive and negative result interpretations must be based on clinical findings and the prevalence of influenza activity.

Rapid influenza diagnostic tests should be confirmed by a molecular assay, such as reverse transcription polymerase chain reaction (RT-PCR) when critical clinical decisions are made.

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