Serum KL-6 in fibrotic NSIP: Correlations with physiologic and radiologic parameters

Fibrotic nonspecific interstitial pneumonia (f-NSIP) has been recognized as a distinct disease entity. KL-6 has been reported to be a useful serum marker in interstitial lung diseases. However, few previous reports evaluated the value of serum KL-6 exclusively in f-NSIP, as distinct from other subtypes of idiopathic interstitial pneumonia, therefore the associations of serum KL-6 with clinical and radiologic findings in this population remain unclear.

Serum KL-6 levels were measured in twenty-six consecutive patients with f-NSIP diagnosed by surgical lung biopsy. Pulmonary function testing, bronchoalveolar lavage, subjective measurement of dyspnea using baseline dyspnea index (BDI), and HRCT were performed in parallel. Two radiologists conducted independent visual examinations of the pattern and extent of abnormalities on HRCT.

Serum KL-6 levels were elevated above the cut-off level in all patients. In univariate analysis serum KL-6 levels showed negative correlations with BDI (rho=-0.52; p<0.01). Serum KL-6 had positive correlations with the extent of several patterns of opacities (rho=0.56-0.62; p<0.01). Among them, only the extent of traction bronchiectasis in HRCT showed significant association with serum KL-6 in multivariate analysis (beta-coefficient=0.043; p<0.01).

Serum levels of KL-6 were elevated in f-NSIP, and were correlated with the extent of fibrotic abnormalities on HRCT, suggesting a value of serum KL-6 as a marker for fibrosis in f-NSIP.