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…
In many laboratories, clinical details on request forms can be structured into a pyramid shape as below.
Let’s take the example of otitis externa.
A good proportion of request forms will be at the bottom of the pyramid, where there are no clinical details present to suggest that otitis externa is the clinical suspicion (as opposed to otitis media, cellulitis of the pinna, or some other condition). Also included in this category are cases where clinical details have been included but are unrelated to sample type, e.g. an ear swab sent with clinical details of “sore throat”. This scenario happens in all sample types with disturbing frequency… (e.g. mid-stream urine sent for a patient with clinical details of chest pain!)
The next level up in the pyramid is where clinical details are present but are insufficient to justify the sample being sent to the laboratory. For example the clinical details might state “Otitis externa“. However most patients with straightforward otitis externa do not need an ear swab sent to the laboratory. Laboratory culture of an ear swab in clinically suspected otitis externa should be the exception as opposed to the rule…
The top level of the pyramid is where clinical details are not only present, but they also give a sound rationale as to why the laboratory is receiving a sample. e.g. “Recalcitrant otitis externa not responding to topical treatment.” or “Diabetic with painful inner ear and fever, clinical suspicion of malignant otitis externa“.
This requesting pyramid applies to most different sample types and clinical scenarios.
At my laboratory, we are doing our utmost to turn this pyramid on it’s head. We have made significant progress to date. In fact our pyramid is starting to look more like a rectangle.
By the end of the year we hope to have removed the base of the pyramid altogether by adopting a policy of having accompanying clinical details pre-requisite for all microbiology tests. I.e. No clinical details, no test.
And that is the way it should be…
Those that know me, will be aware that I am a passionate believer in having clinical rationale and clinical context as pre-requisite for all microbiology samples that are processed by the laboratory.
Exactly the same principles should apply for antibiotic prescriptions…
There are various reasons why a clinician might prescribe an antibiotic:
- Fear: That if an antibiotic is not prescribed, then any suspected infection might increase in severity or even be potentially life threatening.
- Pressure: Pressure to prescribe an antibiotic from the patient or their relatives.
- Action: To be seen to be doing something positive for the patient.
- Justification: That prescribing an antibiotic justifies the cost or time of the consultation.
- Loyalty: If an antibiotic is not prescribed then the patient may go elsewhere to get what they want.
- Bacterial infection: That there is a genuine suspicion of a bacterial infection where the evidence shows that antibiotics are indicated in that particular clinical scenario.
It would be foolish to think that the real prescribing reason is always the last one on this list.
Humans are subject to all sorts of internal biases, and external pressures. We are in essence, fundamentally flawed. It is therefore wrong to expect us to always prescribe antibiotics for the right reasons as opposed to the “not so right” ones.
In other words we need tight controls on our decision making behaviours.
At the moment a clinician can write a prescription for most antibiotics without including any indication as to why the antibiotic was prescribed.
This needs to change.
It is my belief that all antibiotic prescriptions should have the clinical indication for prescribing included on the prescription form as a pre-requisite for dispensing, in both community and hospital settings.
Otherwise the pharmacist is essentially dispensing blindly.
Once such a system is in place, then specific criteria can start to be applied for certain infections in order for an antibiotic prescription to be valid/approved.
Then we can start getting some real controls in place for the purposes of antibiotic stewardship.
The days of clinicians being able to request laboratory tests and prescribe antibiotics without providing a clinical rationale are numbered.