Clinical value of SFRP1, GDF-15, and RBP in the early diagnosis and prognosis of diabetic kidney disease

Purpose To investigate the value of secreted frizzled-related protein 1 (SFRP1), growth differentiation factor-15 (GDF-15), and retinol-binding protein (RBP) levels in the early diagnosis and prognosis of diabetic kidney disease (DKD). Methods This prospective observational study recruited 100 patients with type 2 diabetes mellitus (T2DM) admitted to Zhangjiagang First People's Hospital between July 2022 and June 2023, with sample size calculated based on an expected AUC of 0.85, power of 0.8, and α of 0.05. Participants were categorized based on urinary albumin-creatinine ratio (UACR) into an observation group (early DKD, UACR 30–300 mg/g, n = 50) and a control group (T2DM alone, UACR < 30 mg/g, n = 50). Serum levels of GDF-15 and SFRP1 were measured using enzyme-linked immunosorbent assay (ELISA), and urinary RBP was determined by immunoturbidimetry. Poor prognosis was defined as either a decline in eGFR ≥ 15% over the 2-year follow-up period or initiation of renal replacement therapy. The Δ value was calculated as the difference between the 2-year and baseline measurements. Results The serum SFRP1 level in the observation group was significantly lower than that in the control group, while the serum GDF-15 level and urine RBP level were significantly greater than those in the control group ( P  < 0.05). According to the ROC curve, each of the SFRP1, GDF-15, and RBP levels exhibited good diagnostic efficacy for DKD, but the serum SFRP1 + serum GDF-15 + urine RBP level (combined) had better diagnostic efficacy, and the area under the curve was 0.980 (95% CI: 0.929–0.997) ( P  < 0.001). At baseline, the serum SFRP1 level in the DKD patients with good prognosis was greater than that in the patients with poor prognosis, while the urinary RBP and serum GDF-15 levels were lower than those in the patients with poor prognosis ( P  < 0.05). After 2 years of follow-up, the level of serum SFRP1 was lower in the poor prognosis group, the levels of serum GDF-15 and urine RBP were greater, and the Δ values of all the indices were significantly different ( P  < 0.05). When SFRP1, GFD-15, and RBP were combined, the area under the curve (AUC) of 24-h urine microalbumin (mAlb) for predicting poor outcomes at the 2-year follow-up for DKD patients increased from 0.729 (95% CI: 0.585–0.845) to 0.862 (95% CI: 0.735–0.943). Conclusion Serum SFRP1 levels, serum GDF-15 levels, and urinary RBP levels are novel valuable diagnostic tools for DKD disease and can also improve the prognostic efficacy of 24-h mAlb in DKD patients.