Use of ratio of D-dimer to C-reactive protein as an adjunctive method to differentiate between pulmonary embolism and pneumonia in elderly patients

Seo, Jeongkook; Cho, Jun Hwi; Ohk, Taek Geun; Lee, Hui Young; Park, Chan Woo

J Korean Soc Emerg Med > Volume 32(6); 2021 > Article

Original Article

Journal of The Korean Society of Emergency Medicine 2021;32(6): 561-569.

Use of ratio of D-dimer to C-reactive protein as an adjunctive method to differentiate between pulmonary embolism and pneumonia in elderly patients

, Jun Hwi Cho^1,2

¹Department of Emergency Medicine, Kangwon National University Hospital, Chuncheon, Korea
²Department of Emergency Medicine, Kangwon National University School of Medicine, Chuncheon, Korea
³Department of Internal Medicine, Kangwon National University School of Medicine, Chuncheon, Korea

Correspondence

Chan Woo Park ,Tel: 033-258-2438, Fax: 033-258-2451, Email: bonaeboa@kangwon.ac.kr,

Received: August 25, 2020; Revised: September 25, 2020 Accepted: October 6, 2020. Published online: December 31, 2021.

ABSTRACT

Objective:
Discriminating between pulmonary embolism (PE) and pneumonia in the emergency department (ED) is one of the fastidious tasks. Elderly patients are at more risk of PE and pneumonia than younger patients. This study aimed to determine whether the ratio of D-dimer to C-reactive protein (CRP) could be used as an adjunctive method to differentiate between PE and pneumonia in elderly patients.
Method:
Medical records of patients visiting the ED diagnosed with PE and pneumonia were examined. Cutoff values of D-dimer (μg/mL) and the ratio of D-dimer to CRP ([μg/mL]/[mg/dL]) of subjects with PE or pneumonia were analyzed.
Results:
There were a total of 60 patients with PE and 152 patients with pneumonia. In addition, 15 patients had both PE and pneumonia. The cutoff value of D-dimer to differentiate between PE and pneumonia was 4.26 μg/mL (4,260 ng/mL) (area under curve [AUC], 0.861; sensitivity, 80.0%; specificity, 80.3%; 95% confidence interval [CI], 0.805-0.917). The cutoff value of the ratio of D-dimer to CRP to differentiate between PE and pneumonia was 1.24 ([μg/mL]/[mg/dL]) (AUC, 0.919; sensitivity, 84.4%; specificity, 84.2%; 95% CI, 0.878-0.960).
Conclusion:
The ratio of D-dimer to CRP can be used as an adjunctive method to determine whether a computed tomography pulmonary angiography or a ventilation-perfusion scan can be performed to differentiate between PE and pneumonia in elderly patients.

Key words: Pulmonary embolism; Pneumonia; D-dimer; C-reactive protein