Risk factors and urinary biomarkers of non-albuminuric and albuminuric chronic kidney disease in patients with type 2 diabetes

Figure 1 The design of the study. The study was designed as an observational, single-center, cross-sectional study. Adult men and women with type 2 diabetes (T2D) duration of at least 10 years from the date of diagnosis were included (n = 506). After evaluation for exclusion criteria, 360 patients were included in the analysis. Patients were divided into four groups according to their estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratio (UACR) levels. Individuals with eGFR ≥ 60 mL/min × 1.73 m² and UACR < 3.0 mg/mmol were recorded as patients without chronic kidney disease (CKD) signs (CKD- group). Those with eGFR < 60 mL/min × 1.73 m² and UACR < 3.0 mg/mmol were assigned to the non-albuminuric chronic kidney disease group. Patients with eGFR ≥ 60 mL/min × 1.73 m² and UACR ≥ 3.0 mg/mmol were defined as albuminuric with preserved renal function (A-CKD- group). Individuals with eGFR < 60 mL/min × 1.73 m² and UACR ≥ 3.0 mg/mmol comprised the albuminuric CKD group (A-CKD+). All patients underwent clinical examination, which included an evaluation of diabetes control and in-depth screening/monitoring of complications and comorbidities. The set of clinical risk factors was estimated for each CKD pattern. Urinary excretion of nephrin and podocin, two podocyte-specific markers, and WAP-four-disulfide core domain protein 2, a marker of tubulointerstitial fibrosis, was assessed in T2D patients and the control group (20 subjects without a history of diabetes, obesity or cardiovascular disease). CKD: Chronic kidney disease; eGFR: Estimated glomerular filtration rate; NA-CKD: Non-albuminuric chronic kidney disease; T2D: Type 2 diabetes; UACR: Urinary albumin-to-creatinine ratio; WFDC-2: WAP-four-disulfide core domain protein 2; CKD–: The group of individuals with estimated glomerular filtration rate ≥ 60 mL/min × 1.73 m² and urinary albumin-to-creatinine ratio < 3.0 mg/mmol; NA-CKD: Non-albuminuric chronic kidney disease, the group of individuals with estimated glomerular filtration rate < 60 mL/min × 1.73 m² and urinary albumin-to-creatinine ratio < 3.0 mg/mmol; A-CKD–: Group of patients with estimated glomerular filtration rate ≥ 60 mL/min × 1.73 m² and urinary albumin-to-creatinine ratio ≥ 3.0 mg/mmol; A-CKD+: Group of individuals with estimated glomerular filtration rate < 60 mL/min × 1.73 m² and urinary albumin-to-creatinine ratio ≥ 3.0 mg/mmol.