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Examining the Surprisingly High Impact of Viruses on CAP and the Utility of Procalcitonin in Treatment Decisions

Switching gears to speak about how molecular diagnostics can affect pneumonia treatment decisions, Dr. Wunderink spoke about the procalcitonin test (PCT), which was just approved this year (2017) as a test for use in making important decisions regarding the optimal use of antibiotics in lower respiratory tract infections and sepsis. Dr. Wunderink reviewed the latest in pneumonia molecular diagnostics research, particularly as it is related to PCT.
During his talk, he pointed out that although both PCT and C-reactive protein are inflammatory markers positively correlating with Interleukin 6 (IL-6), only PCT is repressed by interferon (IFN)-gamma. Most importantly, PCT levels above 1.0ng/mL are indicative of a typical bacterial pneumonia infection, while PCT levels at 0.25ng/mL are likely viral, mycobacterial, or unknown.
This test could help manage antibiotic overtreatment, which is something that can increase mortality. To this end, Dr. Wunderink highlighted a study examining survival outcomes for congestive heart failure (CHF) patients with clear-cut pulmonary edema. For patients who had low PCT levels (<0.05) there was much higher rates of survival if they were not treated with an antibiotic.
Ultimately, Dr. Wunderink stressed that when you have an equivocal chest x-ray, it is clear that PCT can be very helpful. He believes it is good to avoid antibiotics in classical CHF with these equivocal chest x-rays and low grade fever. Several studies were reviewed by Dr. Wunderink that showed reduced mortality when antibiotics were used less.
“There still is no paint-by-numbers approach for treating pneumonia,” Dr. Wunderink explained. There are a variety of other considerations. Dr. Wunderink stated that he is not a big fan of using steroids for treating pneumonia, and in fact, he described a randomized controlled trial comparing the effects of steroid use in patients with CAP and high inflammatory response. There was no mortality difference in this study.
In addition, more data is emerging that indicate that there is frequently more of a cardiovascular disease component to what was otherwise previously recognized as pneumonia. Accordingly, Dr. Wunderink, adrenomedullin and troponin are worthy of greater consideration and use in estimating prognosis. Moreoever, thrombocytosis presents as an important association with significantly increased prognostic mortality.
He also stressed the importance of considering the risk for hospital-acquired infections, “For anyone of us hospitalized with pneumonia and no other underlying disease, the probability of us being alive after 1 year is very low.”
In summary, Dr. Wunderink believes PCT levels are helpful for reducing antibiotic use in patients with low risk CAP or viral pneumonia, but that it is important to understand that after a certain point, PCT is no longer a marker of viral versus bacterial, but rather it becomes a marker of general inflammation (somewhere between death and 10 days of antibiotic treatment). More work is needed to examine effects on mortality data.
W. Todd Penberthy, PhD is a medical writer with over 4 years of experience based in Orlando, Florida. Prior to that Todd was a professor directing biomedical research using zebrafish models of human disease with expertise in orthomolecular niacin-related science for 10 years.
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