Researchers discovered that serum Krebs von den Lungen-6 (KL-6) levels are elevated in patients with idiopathic pulmonary fibrosis (IPF) and are hence a useful biomarker to aid in IPF diagnosis, according to results of a new study published in The Clinical Respiratory Journal.

IPF is a commonly seen interstitial lung disease (ILD); it is progressive and carries a poor prognosis. It is also notoriously difficult to diagnose, despite several proposed diagnostic criteria. Diagnosis is overwhelmingly made using high-resolution computed tomography and bronchoscopy.

KL-6 has mainly expressed on the alveolar type 2 cells in the lungs and is released in response to injury. The release of KL-6 allows alveolar type 2 cells to regenerate when injured. KL-6 is already known as a diagnostic marker in ILD, but its specific diagnostic value in IPF has not been verified.

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Jiang and colleagues thus decided to investigate. They recruited 100 patients with IPF in a retrospective study and conducted lung function tests, computed tomography scans, and serological laboratory tests. All the participants gave written consent for the collection of their serum or bronchoalveolar lavage fluid for the purpose of KL-6 analysis.

“The tests showed that there is a significant elevation of KL-6 in IPF patients compared with other ILD and healthy controls,” Jiang and colleagues said.

They discovered that KL-6 is a stable biomarker that is unaffected by smoking or lung infection, though patients with antinuclear antibodies demonstrated higher levels of KL-6. The researchers also discovered that KL-6 levels can indicate the severity of IPF when used in conjunction with pulmonary function and radiological fibrosis scores. 

“This study gave a comprehensive study of initial KL-6 in IPF diagnosis and evaluation, and it was shown that KL-6 was insufficient to assess prognosis,” Jiang et al concluded.


Jiang D, Xiao H, Dong R, et al. Krebs von den Lungen-6 levels in untreated idiopathic pulmonary fibrosisClin Respir J. Published online January 26, 2022. doi:10.1111/crj.13475