Tag Archives: knee aspirates

“The Knee Aspirate….Telling stories”

We receive a lot of knee joint aspirates into our laboratory. But often we don’t know the story as to why the sample has been taken and sent to us…

  • …It might be a elderly patient with a knee replacement who has gradually decreasing mobility over the past 6 weeks.
  • …It might be a young sex worker who has an acutely swollen hot knee with associated fevers.
  • …It might be a middle aged male with a history of recurrent gout.
  • …It might be a patient who got a prosthetic joint inserted a couple of weeks ago and now presents with a discharging wound and fevers.
  • …It might be a patient with osteoarthritis who got a steroid injection into their knee joint a couple of weeks ago and it is now red and painful.
  • …It might be an aid worker who has just returned from working in Sub-Saharan Africa for two years.

or it might be something else altogether.

Who knows? Unfortunately not always the microbiology laboratory.

There are so many ways in which the “story” that comes with the sample can affect the microbiological processing:

  • Whether additional tests in addition to standard culture are indicated?
  • Whether a Gram stain and/or crystal microscopy is performed?
  • What incubation conditions are used (aerobic/CO2/anaerobic) for the culture plates?
  • Which culture media are set up on the sample?
  •  Whether the culture isolates are deemed to be significant or not.
  • Whether susceptibility testing should be performed, and what antimicrobials to test against?
  • Which culture isolates should be reported to the requestor?
  • Which antimicrobial susceptibilities are released to the requestor?
  • Whether an interpretative comment is added to the report, and what the comment should entail?

If we recieve a sample into the microbiology laboratory which has no clinical details on it, then we return the following comment to the requestor:

“No clinical details have been received with this specimen. The lack of clinical information provided to the laboratory represents a potential clinical risk. In the absence of clinical details, optimal test and media selection, susceptibility testing, and result reporting cannot be guaranteed by the laboratory.”

By the end of this year we hope to have introduced a policy of mandatory clinical details in order for laboratory testing to proceed. However, “critical” or “difficult to get” samples such as knee aspirates are always going to have to be exceptions to such a policy. We cannot reject a knee joint aspirate, just because we don’t know the story behind it…

This is a bit of a shame really because ironically it is these types of samples where the clinical details can potentially have the biggest impact on microbiological processing.

And there will always be a small minority of clinicians that will grumble at having to put clinical details on the request form.

Such grumbles are for me however, simply water off a duck’s back…

Michael