Research Objective: To evaluate the prognostic value of serum urea nitrogen to creatinine ratio (sUCR) in the progression of DKD.

Research Design: This study was designed as a multicenter, retrospective cohort study. According to sex and CKD stage , patients are divided into four groups,then evaluate the prognostic value of mean sUCR and ΔsUCR (fluctuation of sUCR over time, meaning monthly rate of change) in the progression of DKD.

Object and source: Patients diagnosed with DKD who meet the inclusion criteria are enrolled into the study.

Observation index: At baseline and every medical visit, therapeutic relevant information was collected. Data mainly include demographic characteristics(age, gender, place of residence, marriage, education degree), lifestyles(smoking, drinking, exercise), clinical characteristics(body mass index, blood pressure, duration , history of CVD, complications, nutrition situation), laboratory indexes (serum creatinine, blood urea nitrogen, glycosylated hemoglobin, urinary albumin to creatinine ratio, 24-hour urinary albumin, 24-hour urine urea nitrogen, etc.).

Quality assurance plan: The present study should be performed according to the principles of the Declaration of Helsinki and has been approved by the Ethics Committee of Guangdong Provincial People's Hospital.

Plan for missing data: When the participants drop out, the researcher should contact the participants by phone, email, text message, letter etc. and ask the reason, making record as full as possible.

Statistical analysis plan: Data are presented as mean±SD for continuous variables and as a number(percentage) for categorical variables. According to sex and CKD stage , patients are divided into four groups,then evaluate the prognostic value of mean sUCR and ΔsUCR (fluctuation of sUCR over time, meaning monthly rate of change) in the progression of DKD. The relationship between baseline characteristics among the four groups was compared by using one-way analysis of variance test, Kruskal-Wallis test or Chi-squared test where appropriate. Survival rates are estimated using Kaplan-Meier analysis, and the significance of differences was analyzed using the log-rank test. Cox proportional hazard regression analysis is used to assess the association between the clinical outcomes and mean sUCR and ΔsUCR. In multivariate analysis, we enter variables using a P value of <0.10 as the selection criterion or considered clinically significant. Hazard ratios (HRs) are presented with 95% CIs. All statistical analysis was performed with the use of SPSS (version 19.0, SPSS, Chicago, USA) and Prism 7.0 (GraphPad Software, San Diego, CA, USA). A two-tailed P value <0.05 was considered to be statistically significant.

Inclusion criteria:

• Patients were diagnosed with DKD, and CKD stages 1-4.

  • Patients' age was between 18-70 years old. ③Clinical datum were complete.

Exclusion criteria:

①Patients were combined with other type of kidney disease; ②Pregnancy women; ③Infection; ④Severe liver disease; ⑤ malignant tumor;⑥Acute heart failure; ⑦Acute cardiovascular and cerebrovascular diseases ⑧gastrointestinal hemorrhage.

DKD was defined as those diagnosed by pathological biopsy, or those with eGFR <60 ml/min per 1.73 m2, or presence of clinically detectable albuminuria over 3 months which is caused by diabetes.