Can serum procalcitonin levels help interpret indeterminate chest radiographs in patients hospitalized with acute respiratory illness?

Background: Clinical diagnosis of pneumonia is difficult and chest radiographs often indeterminate, leading to incorrect diagnoses and antibiotic overuse.

Objective: To determine if serum procalcitonin (ProCT) could assist in managing patients with respiratory illness and indeterminate radiographs.

Design: Subjects were prospectively enrolled during 2 consecutive winters.

Setting: A 520-bed hospital in Rochester, NY.

Patients: Five hundred twenty-eight adults admitted with acute respiratory illness were enrolled.

Measurements: Serum ProCT, admission diagnoses, and chest radiographic findings were used to derive receiver operating characteristics curves to assess predictive accuracy of ProCT for the presence of infiltrates.

Results: Subjects with pneumonia had higher ProCT (median 0.27 ng/ml) than those with exacerbations of chronic obstructive pulmonary disease (0.08 ng/ml), acute bronchitis (0.09 ng/ml), or asthma (0.06 ng/ml). ProCT had moderate accuracy for the presence of infiltrates (area under curve [AUC] 0.72), when indeterminate radiographs were independently classified as infiltrates by a pulmonologist evaluating patients.

Conclusions: ProCT may be useful in diagnosing pneumonia when chest radiographs are indeterminate.