MONTREAL — In community-acquired pneumonia, overuse of broad-spectrum antibiotics can be curbed with the help of biologic markers such as procalcitonin, according to Dr. Jean Chastre of the Hôpital de la Pitié-Salpêtrière, Paris.
Blood levels of procalcitonin (PCT) rise in patients with bacterial infections but remain fairly low in those with viral infections, and PCT levels decrease as the bacterial infection subsides. Measuring PCT levels thus aids decisions about whether to prescribe antibiotics, what type to prescribe, and for how long, said Dr. Chastre at an international conference on community-acquired pneumonia (CAP) that was sponsored by the International Society of Chemotherapy. “We use antibiotics for too long for too many patients, and in doing so are favoring the emergence of resistant strains,” he said in an interview.
“The more antibiotics we use, the more resistance we are going to see,” Dr. Jean-Claude Pechère agreed in an interview. In his presentation, he outlined a 2004 study in which PCT-guided therapy for lower respiratory tract infections significantly reduced antibiotic use, compared with standard care (Lancet 2004;363:600–7). “With these biomarkers, we suddenly realized we could cut antibiotic consumption almost in half. In Europe, we are speaking of millions of patients,” said Dr. Pechère, a professor of medicine at the University of Geneva.
Although a PCT assay is approved in Europe, it is still not widely available, and it is even less so in North America, according Dr. Thomas File, a professor of internal medicine and head of infectious diseases at Northeastern Ohio Universities, Rootstown. “There are a few places where they have it available in the [emergency department], but in most places it takes several hours to get the result back—maybe even a day,” Dr. File said in an interview. Because initiation of antibiotic therapy is recommended within hours of a diagnosis of bacterial CAP, a PCT assay may not be practical for guiding initial treatment decisions, he said. “It's probably going to be more helpful in making decisions about duration of therapy, or changing therapy.”
For example, antibiotics can be stopped if the PCT results suggest that bacterial infection is unlikely, explained Dr. Chastre, who has received research funding and is a speaker for Brahms Diagnostics LLC, which makes a PCT assay. Or, therapy could be shortened if serial PCT measurements suggest a rapid response. “It's probably possible, even in severe pulmonary infection, to shorten the duration of antibiotics to 5 or 7 days if the PCT is decreasing very rapidly,” Dr. Chastre said.
European guidelines recommend that empiric therapy for bacterial CAP should provide coverage against the most common pathogen (Streptococcus pneumoniae) but not atypical pathogens, whereas North American experts favor a wider spectrum of coverage that includes the atypicals. PCT-guided therapy could allow European physicians to continue with less complete initial coverage by identifying the nonresponders who need expanded therapy, Dr. Pechère said.
In the future, it may even be possible to use PCT levels to distinguish typical from atypical CAP pathogens, he added, citing one study that noted lower levels in hospitalized CAP patients infected with typical, compared with atypical, bacteria (Infection 2000;28:68–73). But a more recent study concluded PCT levels were not predictive of type of pathogen (Clin. Microbiol. Infect. 2007;13:153–61).
Dr. Chastre said that in evaluating the severity and progression of pneumonia, PCT levels should always be considered in conjunction with other clinical parameters. “This marker is not 100% sensitive in some patients because, even with very severe disease, some people can have low levels,” he said, citing his own study showing low PCT levels in some patients with ventilator-associated pneumonia (Am. J. Respir. Crit. Care Med. 2005;171:48–53).
The reverse can also be true, with high levels of PCT seen in nonseptic conditions such as trauma, cardiogenic shock, and heat stroke, among others, he said.