Burden and excess risk of adverse outcomes in patients with type 1 diabetes utilizing KDIGO classification: A national cohort study

Objective: The widely adopted KDIGO classification system, "Kidney Disease: Improving Global Outcomes” (KDIGO) has been underutilized in assessing the burden and risk of adverse outcomes in type 1 diabetes. This observational study aimed to clarify how each KDIGO category correlates with outcomes, including mortality in this patient group.

Research design and Methods: In 40,199 diabetes type 1 subjects from the Swedish National Diabetes Register, we examined the: (1) prevalence of different KDIGO categories at baseline; (2) incidence of adverse kidney and cardiovascular (CV) outcomes, including mortality, within each category; and (3) association of baseline category with excess risk of five outcomes (40% decline in estimated glomerular filtration rate [eGFR], kidney failure, major adverse kidney/CV events, all-cause mortality). Cox regression analyses were conducted using three different reference categories: (1) the conventional low-risk "combined G1A1+G2A1"; (2) "G1A1" alone to assess if G2A1 had excess risk; and (3)“G1bA1” alone to evaluate if eGFR ≥105 ml/min had increased risk.

Results: Among 39,067 included patients, with a mean follow-up of 9.1 years, 18.5% presented with chronic kidney disease (eGFR <60 ml/min/1.73m² and/or albuminuria). A progressive increase in incidence and adjusted hazard ratio for all studied outcomes was found with advancing eGFR and albuminuria categories, including in G2A1 (non-CKD). eGFR ≥105 ml/min without albuminuria was not associated with increased risk.

Conclusion: A progressively increasing burden of all studied adverse outcomes was observed with advancing KDIGO categories. Even subjects with preserved eGFR and normoalbuminuria (G2A1) conventionally perceived as non-CKD, had excess risk for all outcomes.