# Rationale and design of the Innsbruck Diabetic Kidney Disease Cohort (IDKDC)—a prospective study investigating etiology and progression of early-stage chronic kidney disease in type 2 diabetes

## TL;DR

This study aims to understand the causes and progression of early kidney disease in type 2 diabetes patients by using kidney biopsies and tracking outcomes over time.

## Contribution

The study introduces a new cohort design to investigate kidney disease etiology in T2D patients through routine biopsies and biomarker analysis.

## Key findings

- The IDKDC study will assess the prevalence of different kidney pathologies in T2D patients with mild-to-moderate kidney impairment.
- Biobanking of biological samples aims to identify biomarkers for better diagnosis and prognosis of diabetic kidney disease.
- The study may support a shift toward routine kidney biopsies for improved risk prediction in T2D patients.

## Abstract

The development of chronic kidney disease (CKD) in about 20%–40% of patients with type 2 diabetes (T2D) aggravates cardiovascular morbidity and mortality. Pathophysiology is of increasing relevance for individual management and prognosis, though it is largely unknown among T2D patients with CKD as histologic work-up is not routinely performed upon typical clinical presentation. However, as clinical parameters do not appropriately reflect underlying kidney pathology, reluctance regarding timely histologic assessment in T2D patients with CKD should be critically questioned. As the etiology of CKD in T2D is heterogeneous, we aim to assess the prevalence and clinical disease course of typical diabetic vs atypical/non-specific vs non-diabetic vs coexisting kidney pathologies among T2D patients with mild-to-moderate kidney impairment [KDIGO stage G3a/A1–3 or G2/A2–3; i.e. estimated glomerular filtration rate (eGFR) 59–45 mL/min irrespective of albuminuria or eGFR 89–60 mL/min and albuminuria >30 mg/g creatinine].

The Innsbruck Diabetic Kidney Disease Cohort (IDKDC) study aims to enroll at least 65 T2D patients with mild-to-moderate kidney impairment to undergo a diagnostic kidney biopsy. Six-monthly clinical follow-ups for up to 5 years will provide clinical and laboratory data to assess cardio-renal outcomes. Blood, urine and kidney tissue specimen will be biobanked to identify diagnostic and prognostic biomarkers.

While current risk assessment is primarily based on clinical parameters, our study will provide the scientific background for a potential change of the diagnostic standard towards routine kidney biopsy and clarify its role for individual risk prediction regarding cardio-renal outcome in T2D patients with mild-to-moderate kidney impairment.