C-reactive protein and D-dimer as possible predictors of clinical characteristics and outcome in community-acquired pneumonia

Objectives A major cause of death in both developed and developing nations is community-acquired pneumonia (CAP). Increased C-reactive protein (CRP) levels in the setting of CAP are linked to the disease’s severity. CAP has drawn attention to D-dimer, a fibrin breakdown product that is mostly utilized to rule out thromboembolic diseases. So the current work aimed to compare CRP and D-dimer as a better predictor of clinical characteristics and outcomes in CAP patients. Patients and methods A prospective study included 300 patients with CAP who were admitted to the Chest Department at Al-Azhar University Hospital of Medicine, Assiut, Egypt between December 2023 and November 2024. Clinical and radiological assessments of all included patients were done. All patients were evaluated by peripheral plasma D-Dimer and CRP tests. Results Crazy pavement and ground glass opacity were linked to considerably higher CRP levels on computed tomography (CT) ( P =0.023 and <0.001, respectively). Significantly higher CRP levels were linked to a CT score of 5 ( P <0.001). Furthermore, D-dimer levels were considerably lower when abnormal plain radiographs were present ( P <0.001). ICU admission, critical pneumonia, need for mechanical ventilation (MV), high confusion, uremia, respiratory rate, blood pressure (CURB) score, and mortality were associated with significantly higher CRP levels ( P <0.001 for all), while the presence of crazy paving on CT was associated with significantly lower D-dimer levels ( P =0.023) and CT score-5 with significantly higher D-dimer levels ( P <0.001). Furthermore, significantly higher D-dimer levels were linked to mortality, ICU hospitalization, and the need for MV ( P <0.001 for all). On the other hand, patients with mild pneumonia and serious pneumonia had the highest D-dimers ( P <0.001). CRP and D-dimer had significant predictive ability to predict the need for MV; cut off value of CRP above 22.85 mg/dl predicted the need for MV with area under the curve (AUC) 0.850 (C.I: 0. 805–0. 895; P =0. 001), 88.9% sensitivity and 65.6% specificity. Cut off value of D-dimer above 0.915 ng/ml predicted need for MV with AUC 0.722 (C.I: 0. 664–l.780; P =0. 001), 91.7% sensitivity, and 51.6% specificity. CRP and D-dimer had significant predictive ability to predict mortality; cut off value of CRP above 33.0 mg/dl predicted mortality with AUC 0.898 (C.I: 0.862–0.934; P =0.000), 87.1% sensitivity and 75.4% specificity. Cut off value of D-dimer above 1.27 ng/ml predicted mortality with AUC 0.898 (C.I: 0.862–0.934; P =0.000), 87.1% sensitivity, and 75.4% specificity. Conclusion In patients with CAP, both CRP and D-dimer seemed to have strong predictive capacity, indicating their possible clinical value in these individuals.