Diagnostic accuracy of C-reactive protein and procalcitonin in suspected community-acquired pneumonia adults visiting emergency department and having a systematic thoracic CT scan

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When I was in training, I was taught that Procalcitonin helped to differentiate between bacterial and viral infections. That's the reason why it was approved by the FDA and that's the reason why we use it today. I have seen other clinicians and colleagues suspect infection on a patient, order a PCT, see that it's negative, and then feel good about everything going on. On the same token, I've seen patients with an elevated PCT who are completely asymptomatic be kept in the hospital for extra days to be "observed" to see whether they will present themselves with an infection within the next 24 hours. Unfortunately, many people have not read the most recent studies where you have to tease out the fact that a negative PCT does not completely rule out infection and vice versa. This study, with a bunch of limitations within it, opened my eyes to the fact that you can have a patient with community acquired pneumonia and a negative PCT. Game changer. I no longer use it to make me feel better inside. I only use it when it's elevated in the first place and I have a confirmed bacterial infection to help me deescalate antibiotics and I also use it to help me know whether source control has been achieved. 

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Procalcitonin: should you use it to guide antibiotic treatment

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Oh my good friend, #procalcitonin, we are doing you so wrong. Sometimes we ignore you to stop antibiotics, sometimes we use you inappropriately to differentiate between bacterial and viral infections and end up under treating bacterial infections. I plan on clearing up a bunch of confusion within the next few months but this shall be article one on the subject. This is where I do feel that checking procalcitonin levels is actually useful and now there’s additional data to support it. Trending it to see if you can discontinue antibiotics early, much to the chagrin of some of my #infectiousdisease colleagues, is a place where it is definitely useful. The caveat is that it has to be elevated in the first place. I’m sure we’ve all seen septic patients with a negative procal at this stage of our careers, as frustrating as that may be. Those are the nuisances of these tests that, if employed correctly, will make you one of the Masters of the Universe. Sorry, my nerd brain is on full swing this morning. 

-EJ

Although great care has been taken to ensure that the information in this post is accurate, eddyjoemd, LLC shall not be held responsible or in any way liable for the continued accuracy of the information, or for any errors, omissions or inaccuracies, or for any consequences arising therefrom.