Background: Biological markers as expression of systemic inflammation have been recognized as useful to evaluate host response in community-acquired pneumonia (CAP). The objective of our study was to evaluate whether biological markers, namely procalcitonin (PCT) and C reactive protein (CRP) might reflect stability after 72 hours of treatment and absence of subsequent severe complications.
Methods: A prospective cohort study was designed in 394 hospitalized patients with CAP. Clinical stability was evaluated using modified Halm's criteria: temperature ≤ 37.2ºC; heart rate ≤100 beats/min; respiratory rate ≤24 breaths/min; systolic blood pressure ≥90 mm Hg; and oxygen saturation≥90% or arterial oxygen partial pressure≥60 mmHg. PCT and CRP were measured on day 1 and after 72 hours. Severe complications were defined as mechanical ventilation, shock and/or intensive care unit (ICU) admission, or death after 72 hours of treatment.
Results: 220 patients reached clinical stability at 72 hours and had significantly lower levels of CRP (4.2 vs 7 mg/dL) and of PCT (0.33 vs 0.48 ng/mL). Regression logistic analyses were performed to calculate several areas under the ROC curve (AUC) to predict severe complications. The AUC for clinical stability was 0.77; 0.84 (p=0.059) when CRP was added; and 0.77(p=0.45) when PCT was added. When clinical stability was achieved within 72 hours and marker levels were below the cut-off points (0.25 for PCT and 3 for CRP) no severe complications appeared.
Conclusions: Low levels of CRP and PCT at 72 hours in addition to clinical criteria might improve prediction of absence of severe complications.