“All samples are equal but some are more equal than others…”

Most samples that arrive into the microbiology laboratory are processed. However there are some where the clinical usefulness of the result must be almost negligible.

Let me give you a few examples…

Swabs of boils that have just been lanced. It is the lancing (draining of pus) which will almost certainly lead to the infection being cured. Much the same applies for peri-anal abscesses.

Swabs of chronic ulcers, including pressure sores. These will almost certainly be colonised by bacteria. Even if a “pathogenic” organism is isolated, it is impossible to say what it means in this setting.

Culturing drain fluids from drainage bags where the drain has been in for more than 5 days. Whatever bacteria are growing in the drainage bag will bear little relation what is growing in the collection that the fluid has come from.

Swabs from ears where the history is of a straightforward otitis externa. Outer ear canals grow all sorts of junk which rarely means much in this clinical setting.

Samples from long term urinary catheters where urine has become cloudy or smelly. This demonstrates that urine has become colonised with bacteria which will always happen eventually when a catheter is in situ. Usually an indication to change the catheter.

Follow up urines after a urinary tract infection has been treated. Rarely indicated, except in pregnancy, pre-urological surgery and in transplant patients. Treat the patient, not the laboratory result.

and the list goes on….

I suspect samples from the above list make up a good 20% of the daily workload of a microbiology laboratory.

But how do you police it?

Not easily. Probably needs a combination of the following:

  • Education of Laboratory Users: Grand Rounds, Clinical Updates etc etc
  • Feedback in the form of a comment added to the test report where the test looks to be unjustified.
  • An insistence on clinical details supporting a rationale for the test.

Regarding the last point, I think the establishment of electronic ordering, which is now starting to come into many labs, may facilitate this, effectively making it impossible to complete test ordering without a supporting clinical rationale for the test.

We process most microbiology samples that come into the lab because it has always been done this way. However with the health budget becoming ever tighter, it is time for the laboratory to move from being the passive recipient and start becoming the gatekeeper for what should be done and what should not.

Think how much time it would free up with at least 20% of the workload gone, and also with the knowledge that the vast majority of specimens that you were working on were genuinely important….


On another topic altogether, click here for an interesting article on looking for anti-microbial substances on the seabed, a good place to look in my opinion.

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