“An imperfect test”

Influenza_virusAs the Influenza season gets underway here in the Southern Hemisphere, I am thinking here about the Rapid Antigen assays that are available for Influenza diagnosis. These are generally very specific, ie a positive result really means a positive. However their sensitivity is not great (70% at best, meaning that a negative result does not always mean that the patient does not have influenza).

This would be ok if it could somehow be ensured that the result was interpreted correctly by the requestor every time.

However even when the results go out with the standard comments expressing the limitations of the test as described above, there is still a tendency for a negative result to be interpreted as the patient not having influenza and the patient to be taken out of isolation etc etc.

In our laboratories we were fortunate enough to get funding for Influenza PCR, so even though the assay takes a bit longer, we know that the sensitivity is much higher than the rapid Influenza tests so a negative is more likely to actually mean a flu free patient.

The rapid test for influenza is only one example amongst many laboratory tests that are “imperfect”.

Given that the result of the rapid Influenza antigen tests are available in 15-20 minutes, it can be a valuable test when in the right hands. Unfortunately, in the wrong hands, it becomes a liability…


On a completely different matter altogether, I have added some MCQs on Pasteurella multocida to the website.

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