Krebs Von Den Lungen-6 as a biomarker for lung disease activity and diagnosis in systemic juvenile idiopathic arthritis
Authors' conclusion
KL-6 is a useful biomarker for discriminating LD and evaluating disease activity in sJIA-LD. Future efforts should focus on the utility of KL-6 for monitoring disease progression, treatment response, and predicting long-term disease trajectories.
Study context
- Population
- Children with systemic juvenile idiopathic arthritis (sJIA) and lung disease (LD); comparators were sJIA patients without LD, children with primary pulmonary alveolar proteinosis (PAP), and healthy control childrenpatients with sJIA-LD enrolled, comparator numbers not printed
- Participants
- 32 children
- Index test or model
- KL-6 as a discriminatory biomarker for LD in sJIA
- Target condition
- lung disease (LD) in systemic juvenile idiopathic arthritis (sJIA-LD)
Methodological detailspatients enrolled through the Childhood Arthritis and Research Alliance (CARRA) Registry
- Patients enrolled through the Childhood Arthritis and Research Alliance (CARRA) Registry
Performance
As reported in the abstract
| Strategy | Sensitivity | Specificity | Positive predictive value |
|---|---|---|---|
| KL-6 cut-off 259.5 U/mL | 81.3% | 80.9% | — not stated in the abstract |
| KL-6 cut-off 371.5 U/mL | 68.7% | 100% | 100% |
Sensitivity
KL-6 cut-off 259.5 U/mL81.3%
KL-6 cut-off 371.5 U/mL68.7%
Specificity
KL-6 cut-off 259.5 U/mL80.9%
KL-6 cut-off 371.5 U/mL100%
Positive predictive value
KL-6 cut-off 259.5 U/mL— not stated in the abstract
KL-6 cut-off 371.5 U/mL100%
— not stated in the abstract
- AUC
- 0.856
- P for AUC
- P < 0.0001
Further findings
| Outcome | sJIA-LD | sJIA without LD | Healthy controls | PAP | P value |
|---|---|---|---|---|---|
| Median KL-6 levelssJIA-LD vs sJIA without LD · significantly higher in sJIA-LD | median 596.3 (IQR 273.5–5,896.3) U/mL | median 193.0 (IQR 151.0–252.0) U/mL | median 171.9 (IQR 89.7–224.3) U/mL | median 1429.9 | P < 0.0001 |
| Median KL-6 levelssJIA-LD vs healthy controls · significantly higher in sJIA-LD | P = 0.001 | ||||
| Median KL-6 levelssJIA-LD vs PAP · no difference | P = 0.30 |
SJIA-LD features associated with higher median KL-6 levels
- Oxygen requirement, abnormal pulse oximeter (<90%), and abnormal chest radiographs
Correlation of KL-6
- Strongly correlated with physician global assessment of lung disease
- Not correlated with markers of systemic inflammation or macrophage activation syndrome
Original publication
Krebs Von Den Lungen-6 as a biomarker for lung disease activity and diagnosis in systemic juvenile idiopathic arthritis. Rheumatology (Oxford). Published 4 November 2026. doi:10.
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