Conclusion. A procalcitonin-directed antibiotic administration guideline did not result in fewer antibiotic days than did usual-care among patients with suspected lower respiratory tract infection.
Commentary
Procalcitonin is a serum biomarker synthesized in thyroid neuroendocrine cells and is the precursor to calcitonin.1 It is undetectable in healthy human serum, but in the setting of systemic inflammation caused by bacterial infection, procalcitonin synthesis is induced in many tissues. Since its discovery in 1970, procalcitonin’s potential utility has been sought in various settings, such as guiding the initiation and/or discontinuation of antibiotics.2
In a prospective randomized trial in patients with an acute chronic obstructive pulmonary disease (COPD) exacerbation, treatment success was not better with antibiotics than placebo in patients with a procalcitonin level < 0.1 µg/L.3 Others replicated these results in COPD patients with acute exacerbation of COPD.4 Another small randomized trial showed that using procalcitonin in intensive care patients reduced antibiotic duration.5 Another small study found similar results in their critical care setting.6 Procalcitonin-guided antibiotic treatment produced similar results in patients with aspiration pneumonia.7 In summary, previously published studies nearly uniformly report reduced antibiotic duration or initiation using procalcitonin cutoffs without increasing adverse events.
In the current study, Huang and colleagues conducted a multi-center randomized trial in 14 academic US hospitals, while simultaneously attempting quality improvement methods for implementing and maximizing compliance with procalcitonin guidelines for local physicians. This study was able to achieve approximately 65% compliance with the guideline, which is relatively lower than in previously reported studies using procalcitonin guidelines. This study was larger and involved more hospitals than the other studies. Interestingly, this study did not find statistically significant differences in antibiotic usage or duration between the procalcitonin group compared to the usual-care group. While this result can be partially explained by the low rate of compliance with the guideline, the result may actually reflect the real-life pattern of procalcitonin guideline usage in clinicians. These results suggest that procalcitonin-based guidelines attempting to reduce antibiotic usage and exposure may be of low value, contrasting with findings from previous studies.
The Huang et al study is well-designed, had a low rate of follow-up loss and withdrawal, was conducted mostly at urban academic hospitals that had a high level of adherence to Joint Commission pneumonia core measures, and had appropriate statistical analyses; however, several factors should be considered when applying the results of this study to clinical practice. First, the large majority (80.1%) of the study cohort had final diagnoses of a COPD exacerbation, asthma exacerbation, or acute bronchitis. These patients had a moderate degree of disease (required hospitalization in 59% of patients with a mean hospital length of stay of 5 days), but their symptoms were severe enough for the patients to present to the emergency department. Patients with a suspected nonrespiratory infection or a milder degree of infection, especially in the ambulatory care setting, may have different antibiotic prescribing patterns. Also, patients in the ambulatory care setting likely have different causal organisms of their diagnosis. Second, this study excluded patients with severe disease who required ICU admission with either septic shock or respiratory failure, patients with pre-existing diseases that placed them at high risk (eg, immunosuppressed patients), and/or patients who had complications of their infection with either a lung abscess or empyema. This pattern of exclusion was widely similar to the other previous procalcitonin studies, which shows that procalcitonin guidelines should not be applied blindly in critically ill patients, even those not requiring ICU admission. Third, patients were excluded from the study if they were on chronic dialysis, had metastatic cancer, or had a recent surgery because of possible elevation of procalcitonin levels without a bacterial infection.