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Summary of the benefits and challenges

Helen Pardoe summarises the benefits and challenges of using procalcitonin outside of the ICU.
Procalcitonin outside the ITU: benefits and challenges. In intensive care, patients are looked after by highly experienced nurses and have 24 hour support from medical staff. ITU teams are familiar with the benefits of using protocols and treatments. However, the majority of patients are treated with sepsis outside of the ITU. Let’s look at how the case presented was managed and consider why.
The first step in the patient’s journey was a call to the ambulance service. So would it be a good idea for a PCT to be taken even earlier in the patient’s journey than the ED? To answer that question, we need to look at the benefit it may give and then consider the balance between the logistics of getting the early sample and the value it adds to the clinical care and patient outcome. The risk of taking a PCT early is that there is a potential to miss a rise in the levels very early in the pathway. And the logistics add cost and time in a hard pressed ambulance service. At the present time in the UK, this would not be recommended.
The second question is more difficult. Taking the test in ED does not add additional work to the frontline clinical staff, although it does add workload to the laboratory services. However, to balance that, C reactive protein levels are taken routinely in EDs across the UK, even recognising their limitations. And as a biomarker for bacterial sepsis, CRP falls below the clinically useful guidance that PCT offers in ED. PCT in ED acts as a baseline to guide further antibiotic prescribing. Two serial PCT levels of 0.2 or below strongly supports review of the need for antibiotics. However, at 48 hours post admission, the CRP and viral or fungal sepsis will remain high so will not give support to reducing antibiotic usage.
Part of routine clinical care in ED for someone with suspected sepsis is delivery of the sepsis 6. And this mandates antibiotics are given within the hour. So even in the face of a low PCT, clinical staff are unlikely to go against clinical guidelines that are current. And it would not be recommended. In addition, it is important to remember that PCT is a support to diagnosis and that delivering basic resuscitation to ensure the patient receives appropriate treatment is a key part of managing sepsis.
We now pick up the case on day three. On day three, a clinical intervention was needed and antibiotics continued. The drop in PCT is reassuring that the sepsis has resolved. However, the raised CRP would continue to cause clinical concern, probably unnecessarily as it is an expression of the maximum CRP levels occurring between 36 and 50 hours after the onset of inflammation, even after appropriate broadspectrum antibiotics have eliminated the source of sepsis. Continuing antibiotics to complete the course would be routine practise and is always the correct approach to good antimicrobial stewardship.
However, the behaviour the prescribing doctor after the first 72 hours, although commonly seen in hospitals around the world and the UK, does not display a good understanding of the biochemistry of the biomarkers they are using and applying them to good antimicrobial stewardship. The correct approach is to follow the local clinical guidelines for antimicrobial prescription, which would recommend a limited course with early transfer to a targeted antibiotic and consideration of conversion from IV to oral delivery at 72 hours. In the case we have reviewed, the doctors had managed the early case appropriately and performed intervention and drainage of the pleural effusion at a suitable time. Changing from broad-spectrum to narrow-spectrum antibiotics is dependent on the results of blood cultures.
However, as the days progressed, in this case, we see that changes to prescription were not considered at an early stage, possibly because of the concern raised by the CRP. And the patient had increased exposure to the risks of antibiotics. And the costs were higher than necessary without any clear clinical benefit without the use of evidence based practise.
So what we see in this case study outside of the ITU, protocols are much more difficult to embed. There’s unwarranted variation in care and non evidence based prescription of prolonged courses of antibiotics. Many of you taking this course already prescribe antibiotics or will in the future. I challenge you to review your previous prescribing habits and lead the way to good antimicrobial stewardship.
At the moment in hospitals across the UK and around the world, prolonged courses of broad spectrum antibiotics lead to common unpleasant complications for patients, vaginal and oral thrush, diarrhoea, nausea, and skin irritation. They can add unnecessary costs, take a significant amount of time to administer, as well as increasing length of stay. If doctors and prescribers always followed local antibiotic guidelines and best practise in prescribing antibiotics, then maybe procalcitonin would not offer much to patient care. However, until we get to that point, using PCT to guide antibiotic prescribing outside of the ICU has real potential to improve patient care and reduce costs. Attached are a few references for further reading.
And next time you’re in a hospital as a member of staff, as a relative, or a patient, ask yourself if the antibiotic prescription you see is really following the science.

Most patients treated with sepsis are outside the intensive therapy unit (ITU).

In the UK, PCT levels are recommended to be taken in the Emergency Department. This allows an early low result to not be mistaken for an overall low level and also is the most logistically feasible. CRP levels are taken routinely throughout the UK in EDs which balances the laboratory workload.

PCT acts as a baseline for antibiotic prescribing. CRP levels in fungal or viral sepsis remain higher for longer so don’t guide antibiotic usage. PCT should be used as a tool to support diagnosis and necessary clinical care should still be delivered to treat sepsis.

PCT can be used in the Sepsis 6 delivery, which mandates those with suspected sepsis are given antibiotics within the hour upon admission. Prolonged courses of broad-spectrum antibiotics can lead to unpleasant consequences for patients. So, using PCT to de-escalate antibiotic usage may improve patient care.

Outside of the ITU, protocols are more difficult to embed.

If Healthcare Professionals followed local antibiotic prescribing guidelines and best practice in prescribing, PCT may offer less to patient care. However, using PCT to guide antibiotic prescribing outside of the ITU currently has the potential to improve patient care and reduce costs.

A larger version of the process map for taking a blood test in the emergency department is available here or in the downloads section below.

Would PCT be useful in your setting? Let us know in the comments below.

References cited in the video have been provided as direct links in the see also section below.

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Procalcitonin: PCT as a Biomarker for Antimicrobial Stewardship

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