#2692 Mayo Clinic Chronicity Score: a helpful tool to establish the prognosis of patients with chronic kidney disease
Authors: Alamo Beatriz Sanchez , Bautista Jose Maria , Romero Sara , de Gracia Núñez Raquel , Casares Beatriz Gil , Molina Fernando Tornero 
Published: May 2024

Abstract

Background and Aims
Kidney biopsy is a useful tool to establish the diagnosis and provide information about the activity and chronicity of kidney disease. Chronic changes are generally irreversible and act as a prognostic marker. The Mayo clinic chronicity score (MCCS) standardizes and semi-quantitatively classifies the degree of chronicity as minimal, mild, moderate, or severe, based on a score assigned according to the degree of glomerulosclerosis, tubular atrophy, interstitial fibrosis, and arteriosclerosis. The objective of this study is to validate and assess whether the MCCS has prognostic value in predicting the initiation of kidney replacement therapy (KRT), death, or doubling of serum creatinine in a cohort of patients with various etiologies of chronic kidney disease (CKD).

Method
We conducted a single-center retrospective study including 101 patients with CKD who underwent native kidney biopsies. The degree of chronicity was classified according to MCCS into 4 categories: minimal (0–1), mild (2–4), moderate (5–7) and severe (8–10). The primary endpoint was defined as KRT, death, and/or a ≥50% increase in baseline creatinine. The kidney endpoint was defined as KRT or a ≥50% increase in baseline creatinine.

Results
The mean age of patients was 52.1 ± 16.8 years, 68.3% were male, with a median baseline creatinine of 1.4 mg/dL (IQR: 0.92-2.1), a median eGFR of 59.6 (33.7-96.8), and median proteinuria of 2.4 g/24 h (IQR: 0.98-3.9). The median follow-up time was 4 years (range: 1.9-6.4). Biopsies yielded a mean of 15.7 ± 8.6 glomeruli. The most frequent etiologies were IgA nephropathy (17.8%), Focal Segmental Glomerulosclerosis (13.9%), membranous nephropathy (11.9%), nephroangiosclerosis (10.9%) and diabetic kidney disease (9.9%). Median chronicity score was 3 (IQR: 1-5). 27 patients (26.7%) had a minimal chronicity score, 37 (36.6%) mild, 30 (29.7%) moderate, and 7 (6.9%) severe. Those patients with severe chronic damage had significantly higher baseline creatinine (p = 0.01), lower eGFR and were older (p = 0.01).
During a median follow-up time of 4 years (IQR: 2-6.3), 10 patients died, 32 (61.9%) reached the primary endpoint, and 24 (28.6%) reached the kidney endpoint. According to the KM curves, patients in the severe chronicity group were at higher risk to meet the primary endpoint (Log-Rank: 21.03 p&lt;0.001), and the kidney endpoint (Log-Rank: 24.9 p&lt;0.001) compared to the other groups (Fig. 1).
In the multivariable Cox regression analysis (adjusted for age, creatinine, sex, proteinuria), the chronicity index was significantly associated with the combined primary endpoint (HR: 6.5, 95% CI: 1.95-21.96, p: 0.002) and the kidney endpoint (HR: 8.6, 95% CI: 2.47-29.75, p: 0.001). The area under the ROC curve for the primary composite endpoint was 0.77 (95% CI: 0.68-0.87) and for the kidney endpoint was 0.79 (95% CI: 0.69-0.89).

Conclusion
The MCCS is a useful tool to predict the prognosis of patients undergoing kidney biopsy, regardless of the etiology of kidney disease. The MCCS could guide therapeutic management and help select patients who benefit from immunosuppressive treatment.