Validation of a renal staging system and its association with renal amyloid deposition burden in AL amyloidosis.

Objectives: This study evaluates the relationship between renal amyloid deposition burden in kidney biopsy and a renal staging system based on proteinuria and estimated glomerular filtration rate (eGFR) in AL amyloidosis.

Methods: A total of 248 patients diagnosed via renal biopsy were included. The extent of amyloid deposition in glomeruli, blood vessels, and tubulointerstitium were evaluated semiquantitatively. The total amyloid load (TA) was defined by the sum of glomerular, vascular and interstitial deposits.

Results: Patients were categorized into three renal stages: I, II, and III. Findings showed that scores of pathological parameters increased progressive with advancing renal stage. The median TA values were 6 (IQR 3-8) in Stage I, 7 (IQR 5-8) in Stage II, and 8 (IQR 7-11) in Stage III (p < 0.001). Baseline eGFR was inversely correlated with TA (r = -0.363, p < 0.001), while proteinuria showed no significant association. Cox regression analysis identified eGFR <50 mL/min/1.73 m² as an independent risk factor for renal survival (HR, 6.519; 95% CI, 3.110-13.665; p < 0.001), whereas proteinuria did not show such an effect.

Conclusions: These findings suggest that in the renal staging system, eGFR - but not proteinuria - is significantly associated with amyloid deposition and independently affects renal survival.