To explore the evaluation value of kerbs von den lungen-6 (KL-6) in the diagnosis and treatment of elderly patients with idiopathic pulmonary fibrosis (IPF).

68 IPF patients with usually interstitial pneumonia admitted to Hongqi Hospital of Mudanjiang Medical College from July 2018 to November 2019 were selected, including 36 elderly IPF patients (elderly IPF group) and 32 non-elderly patients (non-elderly IPF group), another 32 elderly health checkups (the elderly healthy group) were selected as the control. Enzyme-linked immunosorbent assay was used to determine the expression level of serum KL-6, to record the pulmonary function indexes of all IPF patients, and to evaluate the pathological changes of their usually interstitial pneumonia. The serum KL-6 expression levels and lung high-resolution CT (HRCT) scores were compared in each group, and the correlations between KL-6 and lung function indicators and lung HRCT scores were analyzed. The comparison between multiple groups was performed by analysis of variance (the LSD-t test was used for further pairwise comparisons) or the rank sum test, and the comparison of count data was performed by chi square test; correlation analysis was used by Pearson correlation analysis or Spearman rank correlation analysis.

There were statistically significant differences in kL-6 expression levels among the three groups (F=63.425, P < 0.05). The expression level of KL-6 in the elderly IPF group was significantly higher than that of the non-elderly IPF group and the elderly healthy group (P < 0.01). The ROC curve showed that the critical value of KL-6 for diagnosing IPF in the elderly was 516.21 U/ml. At this time, the sensitivity and specificity were the highest, 94.4% and 87.5%, respectively. Regardless of whether the elderly IPF group or the non-elderly IPF group, the serum KL-6 expression level of acute exacerbation patients was significantly higher than that of stable patients (t=2.843, 2.215, P < 0.05 or 0.01). The expression level of serum KL-6 in patients with acute exacerbations in the elderly IPF group was significantly higher than that in the non-elderly IPF group (t=2.657, P < 0.05). Correlation analysis showed that whether it was 68 IPF patients or elderly IPF patients, their KL-6 levels were positively correlated with HRCT scores (r=0.748, 0.699, P < 0.01). The expression level of serum KL-6 in elderly IPF patients was negatively correlated with some restrictive ventilatory function and diffusion function indexes (r=-0.515, -0.393, -0.384, P < 0.05).

Serum KL-6 has certain clinical significance for the diagnosis of IPF patients, especially for elderly patients with IPF, it has a high diagnostic sensitivity and specificity, and it has a certain correlation with the severity of the disease and the treatment effect.