Krebs von den Lungen-6 associated with chest high-resolution CT score in evaluation severity of patients with interstitial lung disease

The purpose of this prospective, single-center study was to measure the value of Krebs von den Lungen-6 (KL-6), a kind of transmembrane mucoprotein, in diagnosing interstitial lung disease (ILD) and in assessing the severity of ILD.

We enrolled 184 patients and 30 healthy controls. Ninety-eight patients were diagnosed with ILD, 47 with pneumonia, 19 with non-small cell lung cancer without ILD (NSCLC/non-ILD) and 20 with other lung diseases. Serum KL-6 levels, CT scores of high-resolution computerised tomography (HRCT) and pulmonary function in ILD patients were assessed.

The mean value of serum KL-6 in patients with ILD, pneumonia, NSCLC/non-ILD, other lung diseases and healthy controls were 1000.67±882.73U/ml, 234.11±91.02U/ml, 269.95±149.23U/ml, 234.85±83.51U/ml and 189.03±55.50U/ml, respectively. Serum KL-6 levels of patients with ILD were significantly higher than that of other groups (P<0.000). The level of serum KL-6 in patients with pneumonia, NSCLC/non-ILD and other lung diseases was also statistically higher than healthy controls (P<0.05). When the cut-off value was 312U/ml, the sensitivity and specificity of KL-6 for the diagnosis of ILD was 84.7% and 85.3% respectively (AUC: 0.936, 95% CI: 0.906-0.965). The serum KL-6 levels in patients with ILD were significantly positively correlated with the CT scores (r=0.539, P=0.000) and negatively correlated with DLCO (r=-0.513, P=0.000).

Serum KL-6 might be useful in the diagnosis of ILD, especially in the hard-to-diagnose cases, with high sensitivity and specificity. Furthermore, KL-6 might be a valuable marker for evaluation of ILD severity.