Supplementary Material for: The Impact of Primary Renal Diagnosis on Prognosis and the Varying Predictive Power of Albuminuria in the NURTuRE-CKD Study

Introduction
The definition of CKD is broad, which neglects the heterogeneity of risk across primary renal diseases.

Methods
The National Unified Renal Translational Research Enterprise (NURTuRE)-CKD is an ongoing UK, prospective multicentre cohort study of 2996 adults with an eGFR of 15–59 mL/min/1.73 m2 or eGFR ≥60 mL/min/1.73 m2 with a uACR >30 mg/mmol. Outcomes and predictive performance of eGFR and uACR were subcategorized by ERA-EDTA primary renal diagnosis (PRD) codes.

Results
2638 participants were included, with baseline median eGFR of 33.5ml/min/1.73m2 and uACR 29.8 mg/mmol. Over a median 49.2 months follow-up, 630 (23.9%) experienced kidney failure (KF), and 352 (13.3%) died before KF, the median eGFR slope was -1.97 ml/min/1.73m2/year. There were significant differences in risk across the PRD, persisting after adjustment for age, sex, baseline eGFR and modifiable risk factors (Blood pressure, HbA1c and renin-angiotensin-aldosterone system inhibitors (RAASi). Diabetic kidney disease, glomerulonephritis and familial/hereditary nephropathy were associated with the greatest risk, while tubulointerstitial disease and vasculitis carried a low risk of KF. eGFR had good predictive accuracy across all PRD. However, the addition of uACR showed variable benefit, depending on the PRD. The largest benefit was seen in vasculitis, renal vascular, and DKD groups, but uACR added no predictive value to the familial/hereditary group.

Conclusion
Significant differences in the risk of kidney related outcomes occurred across the various primary renal diagnoses persisting after adjustment for age, sex, baseline eGFR and modifiable risk factors. Albuminuria's discriminatory ability as a biomarker of progression varies by diagnosis. CKD care should, therefore, take a personalized approach that always considers the primary renal diagnosis.