Clinical and pathological factors associated with progression of diabetic nephropathy
As one of the major complications of diabetes mellitus, diabetic nephropathy (DN) is reported to occur in 30–50% of patients with type 1 DM within 5–10 years after newly diagnosed diabetes and in 20–30% of patients with type 2 DM after a considerable duration of undiagnosed diabetes. DN is traditionally diagnosed based on persist proteinuria, together with reduced renal function. However, people with diabetes may have some isolated or superimposed non‐diabetic renal diseases (NDRDs) on an underlying DN, such as the minimal change disease, IgA nephropathy, and so on. Accordingly, the concept of diabetic kidney disease (DKD) was induced. DKD refers to chronic kidney disease (CKD) that is presumed to be caused by diabetes, which includes isolated DN, isolated NDRD, and a combination of DN and NDRD.4 Some NDRDs are often treatable and even remittable with immunosuppressants, so it is important to differentiate between DN and NDRD early. With regard to this, Zhou et al.5 constructed a differential diagnostic model in type 2 diabetes from 1993 to 2003: PDN = exp(−13.5922 + 0.0371Dm + 0.0395Bp + 0.3224Gh − 4.4552Hu + 2.9613Dr)/[1 + exp(−13.5922 + 0.0371Dm + 0.0395Bp + 0.3224Gh − 4.4552Hu + 2.9613Dr)], where Dm is the diabetes duration (month), Bp is the systolic blood pressure (mmHg); Gh is the HbA1c (%); Hu stands for hematuria (1 yes, 0 no), and Dr denotes diabetic retinopathy (1 yes, 0 no)]. PDN is the probability of DN diagnosis; PDN ≥ 0.5 was regard as DN, otherwise as NDRD. Then, Liu et al.6 examined 200 type 2 diabetes from 2004 to 2012 and constructed a new model with higher accuracy (90.9%): PDN = exp(0.846 + 0.022Dm + 0.033Bp + 2.050Gh − 2.664Hu − 0.078Hb + 2.942Dr)/[1 + exp(0.846 + 0.022Dm+ 0.033Bp + 2.050Gh − 2.664Hu − 0.078Hb + 2.942Dr)].
The reported promotors of DKD include irreversible factors (age, sex, ethnicity, family history, and duration of diabetes) and modifiable factors (hyperglycemia, hypertension, albuminuria, dyslipidemia, and lifestyle). For example, a study involving 227 type 2 diabetic patients showed that proteinuria, hypertension, high levels of HbA1C, and smoking were factors that were independently associated with a faster DKD progression.7 Another study of 1682 diabetic patients with baseline eGFR (estimated glomerular filtration rate) above 60 mL/min per 1.73 m2 revealed that the presence of albuminuria, hypertension, older age, and lower baseline eGFR were predictors of annual renal function decline.