The Difference Between SP-A and KL-6 Levels Responses for Treatment of Interstitial Lung Disease 

Abstract Background The highly variable clinical course of interstitial lung disease (ILD) makes it difficult to determine patients’ prognoses. Serum surfactant protein-A (SP-A) and Krebs von den Lungen-6 (KL-6) were known biomarkers as a monitor of the prognoses. However, the clinical or pathophysiological differences of those biomarkers are not well evaluated. Therefore, through the comparison of the changes of SP-A and KL-6 levels before and after treatment, we investigated the clinical or pathophysiological differences which are embodied by those markers. Methods This study included retrospective data for 71 patients treated for ILD at the First Affiliated Hospital of Guangzhou Medical University between August 2015 and September 2019. Serum SP-A and KL-6 levels were measured before and after treatment. The patients were followed for at least 3 months. Results Changes in the serum biomarkers (Delta SP-A and Delta KL-6) were significantly correlated (rS = 0.482, P < 0.001); Delta SP-A and Delta KL-6 were inversely correlated with changes in pulmonary function (P < 0.05). In a cluster analysis of delta SP-A and KL-6 levels, patients were classified into three groups. In the cluster analysis, in the group in which only SP-A levels decreased after treatment, 50.0% of patients recovered respiratory function and had a significant reduction of serum LDH levels.Conclusions Reduced serum SP-A and/or KL-6 levels were associated with improved lung function in patients with ILD. However, there were patients who showed only a reduction of SP-A levels after treatment. Thus, for proper disease monitoring, measuring both markers are important.