Procalcitonin as a Marker of Etiology in Adults Hospitalized With Community-Acquired Pneumonia

2017年CIDに発表された、3施設 ( Chicago, Illinois, and 2 hospitals in Nashville, Tennessee) によるCAPとプロカルシトニンに関する報告。

Abstract

BACKGROUND

Recent trials suggest procalcitonin-based guidelines can reduce antibiotic use for respiratory infections. However, the accuracy of procalcitonin to discriminate between viral and bacterial pneumonia requires further dissection.

METHODS

We evaluated the association between serum procalcitonin concentration at hospital admission with pathogens detected in a multicenter prospective surveillance study of adults hospitalized with community-acquired pneumonia. Systematic pathogen testing included cultures, serology, urine antigen tests, and molecular detection. Accuracy of procalcitonin to discriminate between viral and bacterial pathogens was calculated.

RESULTS 

Among 1,735 patients, pathogens were identified in 645 (37%), including 169 (10%) with typical bacteria, 67 (4%) with atypical bacteria, and 409 (24%) with viruses only. Median procalcitonin concentration was lower with viral pathogens (0.09 ng/ml; interquartile range [IQR]: <0.05-0.54 ng/ml) than atypical bacteria (0.20 ng/ml; IQR: <0.05-0.87 ng/ml) [p=0.05], and typical bacteria (2.5 ng/ml; IQR: 0.29-12.2 ng/ml) [p<0.01]. Procalcitonin discriminated bacterial pathogens, including typical and atypical bacteria, from viral pathogens with an area under the receiver operating characteristic curve of 0.73 (95% CI: 0.69-0.77). A procalcitonin threshold of 0.1 ng/ml resulted in 80.9% (95% CI: 75.3%-85.7%) sensitivity and 51.6% (95% CI: 46.6%-56.5%) specificity for identification of any bacterial pathogen. Procalcitonin discriminated between typical bacteria and the combined group of viruses and atypical bacteria with an area under the receiver operating characteristic curve of 0.79 (95% CI: 0.75, 0.82).

CONCLUSION

No procalcitonin threshold perfectly discriminated between viral and bacterial pathogens, but higher procalcitonin strongly correlated with increased probability of bacterial pathogens, particularly typical bacteria.

CAP

Clinical signs of CAP, including ≥1 sign of acute infection (fever, chills, hypothermia, leukocytosis, leukopenia, altered mental status) and ≥1 sign of acute respiratory illness (cough, sputum production, chest pain, dyspnea, tachypnea, abnormal lung examination, respiratory failure).

Procalcitonin Measurement

PCT concentrations were measured in research laboratories at the enrolling centers using a VIDAS BRAHMS PCT immunoassay kit (bioMérieux, Marcy l’Etoile, France). The lower limit of PCT detection was 0.05 ng/mL. Study personnel performing PCT measurements were blinded to clinical information, and treating clinicians were blinded to PCT results.

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Limitations

First, 23% of patients enrolled in the EPIC study were not included in this analysis because serum specimens for PCT measurement were not available; this had the potential to introduce a selection bias, but measured clinical characteristics and detected pathogens were similar between the included and excluded patients.

Second, while some protocols recommend serial PCT measurements to guide antibiotic prescribing, we only measured PCT at the time of hospital admission.

Third, invasive diagnostic testing (eg, thoracentesis, bronchoscopy) was only utilized when deemed medically necessary by the treating physicians; study-dictated invasive tests may have resulted in more patients with an identified pathogen.

Fourth, all detected pathogens may not have represented causative agents for pneumonia; for example, viruses detected in NP/OP swabs may have represented infection limited to the upper airways or asymptomatic shedding.

Fifth, we sampled patients for pathogens at the time of hospital admission only; delayed bacterial pneumonias that developed after an initial viral infection would not have been detected with this sampling method.

Finally, all enrolled patients were hospitalized and we are unable to comment on PCT in outpatients with pneumonia.

Conclusion

Although no PCT threshold perfectly discriminated between bacteria and viruses, higher serum PCT strongly correlated with increased probability of a bacterial pathogen.

These data suggest that PCT could assist clinicians in evaluating for potential pathogens, but highlight that basing antibiotic prescribing decisions exclusively on PCT would result in a proportion of patients with bacterial pneumonia not receiving antibiotics.

感想

PCTに依存しすぎないことが重要。CRPのようになっては困りますよね。

私は、CRPとPCT好きでないのですが、簡便な検査であり、これからのの研究に期待してます。今後も、ウオッチ。