Low Proteinuria Linked to Fewer Events in Lupus Nephritis
Key Takeaways
- Among Japanese patients with biopsy-confirmed class III/IV lupus nephritis, lower baseline proteinuria was associated with fewer kidney-failure-or-death events.
- Patients with lower proteinuria had better baseline kidney function and less histologic activity and chronicity.
- Initial glucocorticoids without other immunosuppressants were more common with lower proteinuria, while maintenance-treatment patterns were similar across proteinuria categories.
In a multicenter study of proliferative lupus nephritis, investigators retrospectively reviewed consecutive Japanese cases confirmed by biopsy at 11 hospitals. The analysis included 137 patients with class III/IV disease, with or without class V; 62 (45.3%) had a baseline urine protein-to-creatinine ratio (UPCR) of ≤1 gram per gram of creatinine (g/gCr), and the remainder had UPCR >1 g/gCr. Follow-up ran from biopsy to the last visit or an endpoint: kidney failure, death, or their composite. Investigators assessed histologic activity and chronicity and used Kaplan–Meier comparisons and multivariable Cox models. Physicians selected initial treatment rather than allocating it randomly.
At baseline, the lower-proteinuria group had better kidney function and lower histologic activity and chronicity scores. Class III disease was more frequent and class IV disease less frequent in that group. After a median observation period of 93 months, kidney failure or death occurred in 3/62 (4.8%) versus 22/75 (29.3%) patients, respectively (p<0.001). Kidney failure and death were also individually less frequent with lower proteinuria, and their Kaplan–Meier comparisons differed significantly. In adjusted models, higher baseline proteinuria was associated with death and the composite outcome, but not with kidney failure.
Initial glucocorticoids without other immunosuppressants, irrespective of hydroxychloroquine use, were recorded for 26/62 (41.9%) patients with lower proteinuria versus 18/75 (24%) with higher proteinuria (p=0.04). Maintenance use of glucocorticoids alone and other immunosuppressants was similar across proteinuria groups. Among patients with lower proteinuria, kidney failure, death, and their composite did not differ significantly between those initially receiving glucocorticoids alone and those receiving glucocorticoids plus other immunosuppressants. Adjusted analyses did not associate initial glucocorticoids alone with the studied outcomes.
Physicians selected initial therapy, and patients with lower proteinuria entered follow-up with better kidney function and milder biopsy findings. Those differences could influence both prescribing and prognosis, while the small number of endpoints in the lower-proteinuria group limits the precision of regimen comparisons. A nonsignificant comparison cannot establish treatment equivalence, sufficiency, safety, or absence of an effect. Biopsy selection and the exclusively Japanese cohort limit extrapolation to unbiopsied or non-Japanese populations. The authors noted infrequent use of mycophenolate mofetil and hydroxychloroquine in this Japanese treatment setting.
Patients with biopsy-confirmed proliferative lupus nephritis and lower baseline proteinuria had fewer observed long-term kidney and overall adverse outcomes and may represent a distinct clinical subgroup. More frequent initial glucocorticoid-only use does not demonstrate the comparative efficacy or safety of that regimen.
Clinician Questions
How was kidney failure defined in patients with class III/IV lupus nephritis?
In the Japanese biopsy-confirmed class III/IV lupus nephritis cohort, kidney failure meant a sustained estimated glomerular filtration rate below 15 mL/min/1.73 m² or a need for renal replacement therapy; this was an outcome definition, not a treatment threshold.
Did biopsy-confirmed class III/IV lupus nephritis occur with UPCR below 0.5 g/gCr?
Yes. In the Japanese cohort of biopsy-confirmed class III/IV lupus nephritis, 28 patients in the lower-proteinuria category (UPCR ≤1 g/gCr) had a UPCR below 0.5 g/gCr, indicating variation within that category.