Background Pulmonary involvement is one of the serious complications associated with connective tissue diseases (CTDs), resulting in significant morbidity and mortality.Since interstitial lung disease (ILD) is one of the most serious pulmonary complications associated with connective tissue diseases (CTDs), early diagnosis is important for prognosis and treatmant plan. Krebs von den Lungen-6 (KL-6), which is a glycoprotein secreted by type II alveolar pneumocytes and bronchiolar epithelial cells, which increases in ILDs.

Objectives We aimed to evaluate KL-6 glycoprotein levels in order to find out if it may be a serum diagnostic marker for the CTDs for predicting CTD related ILD development and if there is a difference between pateints and healthy controls.

Methods This study was carried out on the patients applying to the rheumatology polyclinics in Ankara University Faculty of Medicine. We analyzed 45 CTD without lung involvement, 68 CTD related ILD and 45 healthy controls. KL-6 glycoprotein levels were analyzed with ELISA in patients and control group. Demographic and clinic properties of patients were analyzed. The relationship between KL-6 glycoprotein levels and CTD related ILDs was assessed

Results All groups in the study were compared, significantly higher levels of KL-6 were determined in CTD related IAH group, than both healthy control and CTD without pulmonary involvement groups (respectively p<0,001, p<0,008). There were no statistically significance difference between KL-6 levels in healthy control group and CTD without pulmonary involvement (p=0,289). Connective tissue diseases in the diagnostic groups (systemic lupus erythematosus, Sjogren's syndrome, rheumatoid arthritis, mixed connective tissue disease, scleroderma, polymyositis/ dermatomyositis) among them, KL-6 levels did not differ significantly. In the healthy control group, there was statistically signifiance difference between KL-6 levels in smokers and non-smokers. Smokers had significantly higher serum KL-6 levels compared with non-smokers (p<0,05). There was no statistically significance difference between smoking status (pack-year) and serum KL-6 levels. There was no statistically significant correlation between serum KL-6 levels and time since diagnosis of connective tissue diseases and CTD related IAH.

Conclusions In this study, serum KL-6 levels were higher in patients with CTD related IAH than control groups. KL-6 glycoprotein may be used as a serum diagnostic marker for CTD related IAH.

References

1. Doishita S, Inokuma S, Asashima H, Nakachi S, Matsuo Y, Rokutanda R, et al. Serum KL-6 Level as an Indicator of Active or Inactive Interstitial Pneumonitis Associated with Connective Tissue Diseases. Intern Med. 2011;50 (23):2889–92.

2. Hant FN, Ludwicka-Bradley A, Wang H-J, Li N, Elashoff R, Tashkin DP, et al. Surfactant protein D and KL-6 as serum biomarkers of interstitial lung disease in patients with scleroderma. J Rheumatol. 2009 Apr;36 (4):773–80.

Disclosure of Interest None declared