PO30 - Serum KL-6 levels in sarcoidosis and hypersensitivity pneumonitis: a prospective comparative study
Sahajal Dhooria (India)1; Shivani Pundeer (India)1; Mandeep Sadhra (India)1; Amanjit Bal (India)2;
1 - Department of Pulmonary Medicine, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, India; 2 - Department of Histopathology, Postgraduate Institute of Medical Education and Research, Chandigarh;
Keywords: KL-6; sarcoidosis; hypersensitivity pneumonitis;
Select the theme: Challenges in Sarcoidosis Diagnosis and Staging
Type: Original Papers
Presentation: Poster Presentation

Introduction: Krebs von den Lungen-6 (KL-6) is a biomarker of alveolar epithelial injury with established utility in interstitial lung diseases (ILDs). However, its role in granulomatous ILDs, particularly sarcoidosis and hypersensitivity pneumonitis (HP), remains unclear, and comparative data are limited.

Objectives: (1) To evaluate the diagnostic performance of serum KL-6 in granulomatous ILDs, (2) compare levels between sarcoidosis and HP, and (3) assess correlation with baseline lung function.

Materials and Methods: We conducted a prospective, observational, case-control study. Adults (≥18 years) with a multidisciplinary diagnosis of sarcoidosis (with lung parenchymal involvement) or HP were included as cases. Controls comprised healthy individuals and patients with asthma. Serum KL-6 levels were measured using a fluorescent enzyme immunoassay (Tosoh Biosciences). Statistical analyses were performed using SPSS; p<0.05 was considered significant.

Results: Sixty-nine subjects were included (mean age 46.9 years; 57.4% female), including 47 ILD cases (23 sarcoidosis, 24 HP) and 22 controls (9 asthma, 13 healthy). Median serum KL-6 levels (in U/mL) were significantly higher in ILD than in controls (1081 vs. 233 U/mL; p<0.001). Receiver operating characteristic analysis yielded an optimal (Youden’s J-statistic-based) cutoff of 388 U/mL (area under the curve, 0.93; p<0.001), comparable to the manufacturer-recommended cutoff of 381 U/mL). At this cutoff, KL-6 yielded 89.4% sensitivity and 81.8% specificity for distinguishing ILD from controls. KL-6 levels were higher in HP than sarcoidosis (1362 vs. 806 U/mL; p=0.02). In sarcoidosis, fibrotic disease showed higher levels than non-fibrotic disease (1081 vs. 566 U/mL; p=0.03). KL-6 correlated inversely with % predicted FVC in sarcoidosis (ρ = −0.70; p<0.001), but not in the overall ILD cohort.

Conclusions: Serum KL-6 shows good diagnostic performance in granulomatous ILDs. Higher levels in HP than sarcoidosis and associations with fibrosis and lung function in sarcoidosis suggest a potential role in disease differentiation and stratification.

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