ObjectiveTo evaluate the value of carcinoembryonic antigen (CEA), ferritin, D-dimer, fibrinogen degradation product (FDP), white blood cell (WBC) and C-reactive protein (CRP) in diagnosis and prognosis of severe community-acquired pneumonia (SCAP).MethodsThis was a prospective observational study. One hundred and seventy-seven candidates were divided into 3 groups: SCAP group including 61 SCAP patients, CAP group including 56 patients with normal community-acquired pneumonia group and HP group including 60 healthy people. Initial level of above biomarkers was compared and analyzed in the three groups. Then the efficiency of diagnosing and predicting the outcome of SCAP by single and combined index were evaluated by receiver operating characteristic (ROC) curve. Meanwhile the patients in SCAP group were divided into two groups according to the CEA level named CEA increasing group and normal group, between which the differences in prognosis and biomarker level were compared.ResultsThe initial level of all biomarkers increased in two pneumonia groups and exceeded the HP group (P< 0.01) while between SCAP and CAP groups, all indexes in SCAP group were higher than the CAP group (P< 0.001). The areas under the ROC of CEA, ferritin, D-dimer, CRP, WBC and united respectively were 0.800, 0.834, 0.769, 0.898, 0.756 and 0.956. The sensitivity of united index was 91.8% while specificity was 90.5%. Among SCAP group, only CEA level made sense to predict the prognosis (P< 0.01). There were significant differences in intubation rate, mortality, length of RICU stay and FDP, D-dimer between CEA increasing group and normal group (P< 0.05).ConclusionsHigh level CEA, ferritin, D-dimer, CRP and WBC have significant value in diagnosis of SCAP. And the combined index has higher diagnostic value than single one. SCAP with increased CEA level indicates more serious condition and poor prognosis.