Pleural fluid prealbumin and C-reactive protein in the differential diagnosis of infectious and malignant pleural effusions

Qiaoying Ji; Bifei Huang; Maofeng Wang; Zhaoxiang Ren; Sha Zhang; Yongjun Zhang; Lijian Sheng; Yayao Yu; Jinwen Jiang; Debao Chen; Jun Ying; Jiong Yu; Liuyi Qiu; Rugen Wan; Weimin Li

doi:10.3892/etm.2014.1503

Pleural fluid prealbumin and C-reactive protein in the differential diagnosis of infectious and malignant pleural effusions

Exp Ther Med. 2014 Apr;7(4):778-784. doi: 10.3892/etm.2014.1503. Epub 2014 Jan 27.

Authors

Qiaoying Ji¹, Bifei Huang², Maofeng Wang³, Zhaoxiang Ren³, Sha Zhang⁴, Yongjun Zhang³, Lijian Sheng³, Yayao Yu³, Jinwen Jiang³, Debao Chen³, Jun Ying⁴, Jiong Yu⁵, Liuyi Qiu², Rugen Wan³, Weimin Li⁶

Affiliations

¹ Department of Respiratory, Affiliated Dongyang Hospital of Wenzhou Medical University, Dongyang, Zhejiang 322100, P.R. China.
² Pathology Center, Affiliated Dongyang Hospital of Wenzhou Medical University, Dongyang, Zhejiang 322100, P.R. China.
³ Department of Clinical Laboratory Medicine, Affiliated Dongyang Hospital of Wenzhou Medical University, Dongyang, Zhejiang 322100, P.R. China.
⁴ School of Laboratory Medicine, Wenzhou Medical University, Wenzhou, Zhejiang 325035, P.R. China.
⁵ State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310003, P.R. China.
⁶ Department of Internal Medicine, Affiliated Dongyang Hospital of Wenzhou Medical University, Dongyang, Zhejiang 322100, P.R. China.

Abstract

Clinical history and physical examination are helpful in indicating the potential causes of pleural effusions (PEs). However, the accurate diagnosis and establishment of the causes of PE is an ongoing challenge in daily clinical practice. The primary aim of this study was to distinguish between infectious PE and malignant PE (MPE) by measuring two major acute phase response biomarkers: prealbumin (PA) and C-reactive protein (CRP). The study was a prospective trial involving 151 patients who were diagnosed with infectious PE or MPE. Patients with infectious PE were divided into two subgroups: tuberculous PE (TBPE) and parapneumonic PE (PNPE). A further 58 patients with PEs that showed no evidence of MPE, TBPE or PNPE were classified as the chronic non-specific PE (NSPE) group. Demographic characteristics and pleural fluids of the subjects were collected consecutively. The discriminative properties of pleural fluid routine biochemistries, and PA and CRP were evaluated. PA, CRP and classical fluid parameters were also applied to classify patients with infectious PE and MPE. Receiver operating characteristics (ROC) analysis established the cutoffs of PA and CRP for discriminating between groups. Pleural fluid PA levels were significantly higher in the MPE group (n=47) than in the infectious PE group (n=104). Pleural fluid CRP levels were significantly higher in the infectious PE group than in the MPE group. Pleural fluid PA levels were identified to be moderately negatively correlated with CRP levels in the MPE group, with a statistically significant correlation coefficient of -0.352. The ROC curve showed that the sensitivity and specificity of PA for the diagnosis of MPE were 0.851 and 0.548, respectively, at the cutoff of 28.3 mg/l. The area under the curve (AUC) was 0.784 (95% CI, 0.707-0.861). Using CRP as a diagnostic parameter resulted in an comparable AUC of 0.810 (95% CI, 0.736-0.885), at the cutoff of 35.2 mg/l. Combinations of PA and CRP resulted in incrementally discriminating values for MPE, with a sensitivity of 0.617 and a specificity of 0.903. The measurement of PA and CRP levels in pleural fluid may be a useful adjunctive test in PE, as a potential differentiator between infectious PE and MPE.

Keywords: C-reactive protein; pleural effusion; prealbumin.