KL-6 levels help differentiate interstitial lung disease from abnormalities

Background: Krebs von den Lungen-6 (KL-6), predominantly expressed by type II alveolar cells, is linked to the prognosis and severity of interstitial lung disease (ILD). This investigation sought to explore the relationship between KL-6 concentrations and the presence of ILD versus interstitial lung abnormalities (ILA).

Methods: This single-center retrospective study included 147 patients who were suspected of ILD and underwent KL-6 testing between October 2022 and March 2023. Epidemiological and clinical details of the patients, including the outcomes of pulmonary function tests and computed tomography findings, were retrospectively extracted from electronic medical records.

Results: The average age within the cohort was 77.1 years, with 97.3% (143 patients) being male. Notably, the ILA group displayed significantly reduced levels of KL-6 compared to the ILD group (411.6±298.8 vs. 968.8±901.9 U/mL, P<0.001). Utilizing a threshold of 410 U/mL for KL-6, the diagnostic performance yielded an area under the curve (95% CI) of 0.727 (0.605–0.849), demonstrating a sensitivity of 80.8% and a specificity of 64.7%.

Conclusions: Our findings indicate that serum KL-6 concentrations are markedly elevated in patients with clinically recognized and treated ILD compared to those identified with ILA. Furthermore, the association between higher KL-6 levels and reduced forced vital capacity percentage underlines the biomarker's potential in differentiating between ILD requiring intervention and less severe abnormalities.

Key findings

• Serum Krebs von den Lungen-6 (KL-6) levels are significantly elevated in patients with interstitial lung disease (ILD) compared to those with interstitial lung abnormalities (ILA), indicating its potential as a diagnostic biomarker.

What is known and what is new?

• KL-6 is predominantly expressed by type II alveolar cells and is linked to the prognosis and severity of ILD.

• The study provides evidence that serum KL-6 concentrations are markedly elevated in clinically recognized and treated ILD compared to ILA. It also highlights the relationship between KL-6 levels and pulmonary function, specifically forced vital capacity.

What is the implication, and what should change now?

• Clinicians could consider incorporating KL-6 assessments into the diagnostic process for patients with suspected ILD to improve early detection and management strategies. Further research may be warranted to establish standardized protocols for KL-6 testing in clinical settings.