Tag Archives: influenza pcr

“Susceptibility to Influenza”

If you live in the Northern Hemisphere you may have found that your laboratory was swamped by incoming influenza tests this season?

You would not be alone.

Influenza is an unpredictable beast. In my own neck of the woods, New Zealand, the 2015 season was busier than usual, the 2016 season was almost non-existent, and the 2017 season was very average.

Nobody knows what will happen with influenza during 2018.. (Note that as NZ is in the Southern Hemisphere, our winter is June, July , August, right in the middle of the year).

Often you will see Influenza “experts” on TV making predictions about how severe the forthcoming influenza season will be. However such predictions come with huge pinches of salt. You might well be better off predicting the stock market…

The truth is that we don’t really know how bad the forthcoming influenza season is going to be, whether you are an expert or just an interested bystander.

And as a result we have no idea how much each influenza season is going to cost a diagnostic laboratory that performs influenza testing.

Let’s say a bog standard Influenza/RSV PCR costs approximately $30. In a quiet season 1000 tests might get performed in a medium sized hospital. However in a busy season 5000 tests might be required, with an excess cost of $120000. This would of course cause the laboratory manager some sleepless nights!

I am glad I am not a laboratory manager..

And then there might be an influenza pandemic…

The same goes for Public Health Laboratories. The numbers of samples coming in for antigenic sub-typing will be closely related to the severity of the influenza season.

Contracts that laboratory providers have with healthcare funders need to take this unpredictability into account. Some sort of clause like “The diagnostic laboratory will perform up to X Influenza PCRs during the Influenza season. If this number is exceeded, further funding will be negotiated”. Unfortunately this is often not the case. Often laboratory providers will be so desperate to get the contract signed and sealed that they will accept these risks, and manage such problems reactively.

From a financial point of view, microbiology laboratories are very susceptible to influenza test volumes, just like they are susceptible to emerging diseases and MDROs, cohorts where “unexpected testing” may need to take place.

There will of course be some laboratories who are reimbursed per test performed (fee for service). Those places of course would be hoping for a pandemic every year!, but such laboratories/funding arrangements are getting less and less common. The funders are not daft!

I hope for a quiet influenza season this year, and that is nothing to do with my personal risk! (I look forward to receiving the quadrivalent vaccine in the next couple of months).


“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.