Circulating kidney injury molecule-1 as a prognostic biomarker for long-term renal outcomes in lupus nephritis: a...

To determine whether circulating kidney injury molecule-1 (KIM-1) predicts long-term renal outcomes in lupus nephritis (LN), including relapse, progression to end-stage kidney disease (ESKD) and mortality.

This retrospective cohort study included 63 Japanese patients with biopsy-confirmed LN who were treated at Kanazawa University Hospital between 1990 and 2022. After excluding 17 patients who did not meet the eligibility criteria, 46 patients were included in the final analysis. Circulating KIM-1 levels were measured in serum samples collected at the time of renal biopsy prior to treatment or additional treatment. Patients were stratified into low-KIM-1 and high-KIM-1 groups using the median value (153 pg/mL) as the cut-off. The primary endpoints were LN relapse, ESKD and all-cause mortality. Survival was analysed using Kaplan-Meier curves and Cox proportional hazards models.

During a median follow-up of 127 months, nine patients (20%) experienced relapse, four (9%) developed ESKD and six (13%) died. The high-KIM-1 group had lower baseline renal function, greater proteinuria, a higher frequency of Class IV histology and higher activity index scores. Kaplan-Meier analysis demonstrated significantly lower LN relapse-free (p=0.027; log-rank) and ESKD-free survival (p=0.049) in the high-KIM-1 group. In the multivariable Cox regression analysis, circulating KIM-1 was independently associated with LN relapse (per-IQR HR: 1.92, 95% CI 1.07 to 3.45; p=0.029).

Elevated circulating KIM-1 at the time of renal biopsy was associated with adverse long-term renal outcomes in LN and independently associated with relapse, although its incremental predictive value beyond conventional clinical markers was modest. KIM-1 may support early risk stratification and individualised treatment; however, prospective validation in larger cohorts is needed.