Serum human epididymis protein 4 level as a predictor of clinical worsening in idiopathic pulmonary arterial hypertension: a pilot study

Background Human epididymis protein 4 (HE4) was proved to be a novel biomarker for left heart failure. The purpose of this exploratory study was to evaluate the role of HE4 in patients with idiopathic pulmonary arterial hypertension (IPAH) who usually have concurrent right heart failure. Methods 55 patients with newly diagnosed IPAH were continuously enrolled and serum HE4 levels were assessed at baseline. All patients were followed up from the date of blood sampling, and a composite endpoint of clinical worsening was detailedly recorded. Results Serum levels of HE4 were significantly higher in IPAH patients than healthy controls (6.9 ± 2.2 vs 4.4 ± 0.9 ng/ml,p < 0.05) and increased as cardiac function deteriorated. HE4 levels correlated with endothelin-1 (r = 0.331,p < 0.01) and right atrial pressure (r = 0.30,p < 0.03). After a mean follow-up of 20 ± 10 months, 13 patients experienced clinical worsening. Receiver operating characteristic analysis showed that HE4 levels > 6.5 ng/ml discriminated clinical worsening with a sensitivity of 92.31% and a specificity of 59.52% (area under the curve [AUC] = 0.81). Multivariate Cox regression analysis demonstrated that HE4 (χ2: 5.10; hazard ratio [HR] = 1.26; 95% confidence interval: 1.03 to 1.55,p < 0.02) and pulmonary vascular resistance (χ2: 4.19; HR = 1.14; 95% confidence interval: 1.00–1.29,p < 0.04) were independently predictive of clinical worsening. Patients with HE4 > 6.5 ng/ml had a worse 2-year survival rate than those with HE4 ≤ 6.5 ng/ml (58.9% vs 96.2%,p < 0.001). Conclusions Serum levels of HE4 were elevated in IPAH patients and correlated with disease severity. HE4 was an independent predictor of clinical worsening in IPAH patients.