Key Points

Patients with AA amyloidosis and age ≥65 years, eGFR 1000 ng/L and/or type-B natriuretic peptide >130 ng/L at diagnosis have poorer survival.Proteinuria >3.0 g/24 hours and eGFR

Background

The kidney is involved in almost 100% of cases of AA amyloidosis, a rare disease caused by persistent inflammation with long overall survival but frequent progression to kidney failure. Identification of patients with advanced disease at diagnosis is difficult, given the absence of validated staging systems.

Methods

Patients with newly diagnosed AA amyloidosis from the Pavia (n=233, testing cohort) and Heidelberg (n=243, validation cohort) centers were included in this study. Cutoffs of continuous variables were determined by receiver operating characteristic analysis predicting death or dialysis at 24 months. Prognostic factors included in staging systems were identified by multivariable models in the testing cohort.

Results

Age ≥65 years, eGFR 130 ng/L and/or N-terminal type-B natriuretic peptide >1000 ng/L) were associated with overall survival and included in the staging system (all with simplified coefficients 1). Mean 36-month overall survival was lower with higher staging system scores (score 0–1: 92%; score 2: 72%; score 3: 32%). These results were confirmed in the validation cohort. For kidney failure, variables selected to enter in the staging system model were proteinuria >3 g/24 hour and eGFR

Conclusions

We identified and validated biomarker-based staging systems for overall survival and kidney failure in AA amyloidosis.