Pharmacy Guided Procalcitonin Ordering in Adult Inpatients with Lower Respiratory Tract Infections
By: Dr. Katie Dircksen, Dr. Riley Bowers, Dr. Dustin Bryan, Ms. Emily Woodfield, and Dr. Serina Tart
Introduction
Lower respiratory tract infections are among the most common diagnoses for antibiotic prescriptions; however, a study by the Center for Disease Control (CDC) found that 86% of patients presenting with pneumonia had either a viral infection or lacked an identifiable pathogen.1,2 Lower respiratory tract infections (LRTI) can be diagnosed via microbiologic testing, but culture results can take days and often do not identify the causative organism(s). Consequently, the diagnosis of LRTI in the emergency department (ED) is based on symptoms and clinical history. Symptoms of LRTI include cough, sputum production, dyspnea, tachypnea, pleuritic pain, rales, crepitation, and signs of infection (core body temperature >38.0°C, leukocyte count >10,000/µL or <4000/µL).3 With these symp-
PCT concentration elevations secondary to bacterial infections typically rise within 2-4 hours of an inflammatory trigger and reach their peak at approximately 2448 hours. Peak concentrations may be higher depending on the severity of the infection and deProcalcitonin (PCT) is an inflam- cline quickly at a predictable rate matory marker that can indicate with the resolution of inflammathe presence of a bacterial infec- tion.1 tion.5 In patients without an acute bacterial infection, this lab value Due to the specificity for bacteriis typically undetectable (<0.07 al infection, a high PCT level has mcg/L). Triggers that cause in- a positive predictive value indiflammation specific to bacterial cating that antibiotics are necinfections include microbial tox- essary. If the PCT level is low, a ins (i.e., endotoxins) and cyto- non-bacterial cause for the pakines (tumor necrosis factor (TF- tient’s symptoms should be conN)-alpha, interleukin-1 beta, and sidered.6 In 2012 a Cochrane interleukin-6). In contrast, viral review showed that an initial infections lack PCT synthesis due assessment of PCT levels resultto cytokines released by the virus ed in the reduction in antibiotic that inhibit TNF-alpha production use by 60-70% in patients with and thus prevent inflammation.5 low-severity respiratory tract infections.7 The same Cochrane
toms being of low specificity, it is easy to misdiagnose a patient with LRTI when they truly have another diagnosis, such as an exacerbation of chronic obstructive lung disease (COPD), heart failure (HF), or asthma.4
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