Value of Human Epididymis Secretory Protein 4 in Differentiating Malignant from Benign Pleural Effusion: an Analysis of Two Cohorts

Background: Lung cancer is the most common cause of malignant pleural effusion (MPE). Serum human epididymis secretory protein 4 (HE4) is a useful diagnostic marker for lung cancer. Objective: This study aimed to evaluate the diagnostic accuracy of pleural fluid HE4 for MPE. Design: A prospective, double-blind diagnostic test accuracy study. Methods: Patients with undiagnosed pleural effusion were enrolled in two cohorts (Hohhot and Changshu). Electrochemiluminescence immunoassay was used to detect pleural fluid HE4. The diagnostic accuracy of HE4 was evaluated by a receiver operating characteristic (ROC) curve, and the net benefit of HE4 was assessed by a decision curve analysis (DCA). Results: A total of 66 MPEs and 86 benign pleural effusions (BPEs) were enrolled in the Hohhot cohort. In the Changshu cohort, 26 MPEs and 32 BPEs were enrolled. In both cohorts, MPEs had significantly higher pleural fluid HE4 than BPEs. The area under the ROC curve (AUC) of HE4 was 0.73 (95% CI: 0.64–0.81) in the Hohhot cohort and 0.79 (95% CI: 0.67–0.91) in the Changshu cohort. At a threshold of 1300 pmol/L, HE4 had sensitivities of 0.44 (95% CI: 0.33–0.56) in the Hohhot cohort and 0.54 (95% CI: 0.35–0.73) in the Changshu cohort. The corresponding specificities were 0.90 (95% CI: 0.83–0.95) in the Hohhot cohort and 0.94 (95% CI: 0.84–1.00) in the Changshu cohort. In subgroup analyses, HE4 had an AUC (95% CI) of 0.78 (0.71–0.85) in exudates and an AUC of 0.69 (0.57–0.81) in patients with negative effusion cytology. The DCA revealed that HE4 determination had a net benefit in both cohorts. Conclusion: Pleural fluid HE4 has moderate diagnostic accuracy for MPE and has net benefit in pleural effusion patients with unknown etiology.