Krebs von den Lungen-6 (KL-6): le nostre evidenze in fibrosi polmonare da COVID-19 e asma grave

Introduction: Krebs von den Lungen-6 (KL-6) is an extracellular mucinous glycoprotein expressed by alveolar epithelial cells, which, when damaged, allow its diffusion into the bloodstream. This study aimed to evaluate the potential role of KL-6 in COVID-19-related pulmonary fibrosis and severe asthma. Additionally, a comparison was conducted between two different analytical platforms (TOSOH Bioscience, Turin, Italy) characterized by distinct detection technologies: immunochemiluminescence (AIA-CL300) and immunofluorescence (AIA-360). Methods: Two hundred forty-nine residual serum samples from 215 patients with COVID-19-related pulmonary fibrosis and 80 samples from patients with severe asthma were analyzed using AIA-360. As a control group, 122 samples from healthy subjects were used. Additionally, 25/215 patients with pulmonary fibrosis were monitored over time for KL-6 levels. For the method comparison study, 93 samples were analyzed. Results: A statistically significant difference in KL-6 levels was observed between the control group and both patients with pulmonary fibrosis (p<0.0001) and patients with severe asthma (p=0.005). Moreover, KL-6 values above the reference interval were associated with a worse outcome (Odds Ratio 23.33, p<0.004). Furthermore, KL-6 levels showed a negative correlation with alveolar-capillary diffusion of carbon monoxide (%DLCO) (r=-0.54, p<0.0001). In patients with %DLCO <80%, a statistically significant difference was observed between baseline and follow-up KL-6 values (p=0.0036). The method comparison study demonstrated good comparability and agreement (Cohen’s Kappa=0.78). Discussion: KL-6 measurement can provide valuable biochemical information correlating with clinical and pulmonary function parameters, making it a surrogate marker for %DLCO in predicting patients’ outcome and in monitoring disease progression.