SEATTLE – Procalcitonin, a marker of bacterial infection, rises and peaks sooner than C-reactive protein (CRP), and is especially useful to help rule out invasive bacterial infections in young infants and pediatric community acquired pneumonia due to typical bacteria, according to a presentation at the 2019 Pediatric Hospital Medicine Conference.
M. Alexander Otto/MDedge News
(From left) Dr. Marie Wang, Dr. Russell McCulloh, and Dr. Nivedita Srinivas
It’s “excellent for identifying low risk patients” and has the potential to decrease lumbar punctures and antibiotic exposure, but “the specificity isn’t great,” so there’s the potential for false positives, said Russell McCulloh, MD, a pediatric infectious disease specialist at the University of Nebraska Medical Center, Omaha.
There was great interest in procalcitonin at the meeting; the presentation room was packed, with a line out the door. It’s used mostly in Europe at this point. Testing is available in many U.S. hospitals, but a large majority of audience members, when polled, said they don’t currently use it in clinical practice, and that it’s not a part of diagnostic algorithms at their institutions.
Levels of procalcitonin, a calcitonin precursor normally produced by the thyroid, are low or undetectable in healthy people, but inflammation, be it from infectious or noninfectious causes, triggers production by parenchymal cells throughout the body.
Levels began to rise as early as 2.5 hours after healthy subjects in one study were injected with bacterial endotoxins, and peaked as early as 6 hours; CRP, in contrast, started to rise after 12 hours, and peaked at 30 hours. Procalcitonin levels also seem to correlate with bacterial load and severity of infection, said Nivedita Srinivas, MD, a pediatric infectious disease specialist at Stanford (Calif.) University (J Pediatr Intensive Care. 2016 Dec;5[4]:162-71).
Due to time, the presenters focused their talk on community acquired pneumonia (CAP) and invasive bacterial infections (IBI) in young infants, meaning essentially bacteremia and meningitis.
Different studies use different cutoffs, but a procalcitonin below, for instance, 0.5 ng/mL is “certainly more sensitive [for IBI] than any single biomarker we currently use,” including CRP, white blood cells, and absolute neutrophil count (ANC). “If it’s negative, you’re really confident it’s negative,” but “a positive test does not necessarily indicate the presence of IBI,” Dr. McCulloh said (Pediatrics. 2012 Nov;130[5]:815-22).
“Procalcitonin works really well as part of a validated step-wise rule” that includes, for instance, CRP and ANC; “I think that’s where its utility is. On its own, it is not a substitute for you examining the patient and doing your basic risk stratification, but it may enhance your decision making incrementally above what we currently have,” he said.
Meanwhile, in a study of 532 children a median age of 2.4 years with radiographically confirmed CAP, procalcitonin levels were a median of 6.1 ng/mL in children whose pneumonia was caused by Streptococcus pneumoniae or other typical bacteria, and no child infected with typical bacteria had a level under 0.1 ng/mL. Below that level, “you can be very sure you do not have typical bacteria pneumonia,” said Marie Wang, MD, also a pediatric infectious disease specialist at Stanford (J Pediatric Infect Dis Soc. 2018 Feb 19;7[1]:46-53).
As procalcitonin levels went up, the likelihood of having bacterial pneumonia increased; at 2 ng/mL, 26% of subjects were infected with typical bacteria, “but even in that group, 58% still had viral infection, so you are still detecting a lot of viral” disease, she said.
Prolcalcitonin-guided therapy – antibiotics until patients fall below a level of 0.25 ng/ml, for instance – has also been associated with decreased antibiotic exposure (Respir Med. 2011 Dec;105[12]:1939-45).
The speakers had no disclosures. The meeting was sponsored by the Society of Hospital Medicine, the American Academy of Pediatrics, and the Academic Pediatric Association.