Human epididymitis protein 4 as a biomarker of interstitial lung disease in patients with idiopathic inflammatory myopathies.

Objectives: Human epididymis protein 4 (HE4) inhibits the degradation of type I collagen, thus promoting fibrosis. We aimed to investigate serum HE4 levels in patients with idiopathic inflammatory myopathies (IIMs), as potential biomarker of interstitial lung disease (ILD).
Methods: IIMs patients followed in our centre between June 2020 and January 2023 were enrolled. ILD was detected by high-resolution computed tomography (CT) and pulmonary function tests. Serum HE4 levels were measured in patients and controls. Progressive fibrosing (PF-) ILD was evaluated in patients with available 2-year follow-up (INBUILD criteria).
Resilts: We enrolled 90 consecutive IIMs patients (68% females, mean age 59.5 [52.75- 66.0] years) and 42 healthy, age- and sexmatched controls. ILD was diagnosed in 44 (49%) patients. Serum HE4 levels were higher in IIMs patients than controls: 78.55 [54.6-114.4] vs. 51.05 [41.8-62.8] pmol/L (p=0.001). IIMs-ILD patients had higher levels of HE4 vs. those without ILD (193.7 [78.92-137.42] vs. 58.15 [48.32-79] pmol/L, p<0.0001). Serum HE4 levels correlated inversely with diffusing capacity for carbon monoxide (rho=-0.556, p<0.0001) and total lung capacity (rho=-0.459, p=0.001). Serum HE4 levels were the only variable independently associated with IIMs-ILD in two models of multivariate analysis: OR 1.063 (CI 95% 1.02-1.108), p=0.004, and OR 1.059 (CI 95% 1.020-1.099), p=0.003. PF-ILD was detected in 39.4% of IIMs-ILD patients with available follow-up (33/44), without any significant association with baseline serum HE4 levels.
Conclusions: HE4 might be a useful biomarker in the identification and assessment of ILD in IIMs patients.