Procalcitonin can help predict which patients with community-acquired pneumonia may require intubation for respiratory failure during a hospital admission.
Compared to those with undetectable levels, patients with a procalcitonin of 5 ng/mL were three times more likely to require invasive respiratory support, and those with a 10 ng/mL level were five times more likely, reported Wesley Self, MD, and his colleagues (Chest. 2016;150[4]:819-28. doi: 10.1016/j.chest.2016.04.010).
While predictive accuracy isn’t good enough to merit use of procalcitonin as a stand-alone test, adding it to existing clinical management tools “is likely to improve identification of patients needing intensive care,” wrote Dr. Self of Vanderbilt University, Nashville, and his colleagues. “An elevated procalcitonin level may help identify these patients without overt clinical signs of impending respiratory failure or shock but who would benefit from early [intensive care unit] admission.”
The team examined serum procalcitonin as a biomarker in a subgroup of patients included in the Etiology of Pneumonia in the Community (EPIC) study of adults hospitalized with community-acquire pneumonia. The primary outcome was the need for invasive respiratory and/or vasopressor support (IRVS) within 72 hours.
Secondarily, they looked at whether adding procalcitonin boosted the performance of accepted pneumonia risk scores, including the American Thoracic Society minor criteria (ATS).
The cohort comprised 1,770 patients with a median age of 57 years. Of these, 115 (6.5%) needed IRVS within 72 hours of admission. Almost 16% were admitted directly into an intensive care unit; almost 7% experienced a delayed transfer from a medical unit into an ICU. The in-hospital mortality was about 2%.
Most (1,642) had an ATS score of less than 3; among these, about 5% needed IRVS. The remainder had a score of 3 or higher; about 30% required IRVS. All had procalcitonin levels pulled at admission. The levels were significantly higher among patients who required IRVS than those who didn’t (1.43 ng/mL vs. 0.14 ng/mL).
A multivariate analysis found that procalcitonin was strongly associated with the risk of IRVS. In patients with undetectable levels, the risk was 4%. At 5-10 ng/mL, the overall risk of IRVS was about 14%. Every 1-ng/mL increase in this range boosted the risk of IRVS by 1%-2%.
Adding the measurement of procalcitonin to traditional pneumonia severity risk scores significantly improved the patients’ performance. When stratified by ATS minor criteria, the risk of IRVS was 4.7% among low-risk patients. That decreased to 2.4% with the addition of undetectable procalcitonin, and increased to 12% with the addition of a 10 ng/mL level.
Conversely, without considering procalcitonin, ATS high-risk patients had almost a 30% risk of IRVS. Among these high-risk patients, IRVS risk dropped to 13% with undetectable procalcitonin and increased to 36% with high procalcitonin.
Adding the biomarker level to the ATS system improved its ability to correctly classify patients, the team said. “Using at least 3 ATS minor criteria alone to indicate high risk, 77 (4.4%) of the 1,770 total patients were misclassified as low-risk and experienced IRVS. Including procalcitonin of at least 0.83 ng/ml in addition … as a high-risk indicator reduced the number of patients with IRVS misclassified as low risk to 44 (2.5%). Adding procalcitonin of at least 0.83 ng/mL as a high-risk indicator resulted in 370 additional patients being classified as high risk, with 33 correctly classified as having IRVS.”
Dr. Self reported financial relationships with multiple pharmaceutical companies.
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