Objective To explore the effect of urine mixing degree on 24-hour urinary total protein(24 h UTP)in patients with chronic kidney disease(CKD).Methods From October 1,2023 to December 31,2023,30 hospitalized patients who needed to complete 24 h UTP testing in Zhongshan Hospital,Fudan University were selected.A 5 L unified container was used to collect urine for 24 hours.After collection and one hour's standing,the urine sample was divided into upper,middle,and lower equal parts according to volume,which was defined as direct-sampling group.Then,the urine samples were fully mixed with a magnetic stirrer and sampled again according to the above-mentioned three-equal sampling method,which was defined as mixed-sampling group.The generalized estimating equation was used to compare the urinary protein concentration before and after mixing and at different sampling location.Results The results of generalized estimating equation showed that after controlling the variable"sampling position",there was no significant difference in urinary protein concentration between the direct-sampling group and the mixed-sampling group.After controlling the variable"mixing method",there was still no significant difference in urinary protein concentration at different sampling positions.After adjusting the covariates such as age,gender,and estimated glomerular filtration rate(eGFR),the results were consistent.Conclusions With standard protocol,the entire 24-hour urine sample is a relatively even-distributed solution.After the total urine collection is completed,the temporary sample can be directly extracted from any level of the original urine within 1 hour,and the urine protein concentration of the sample multiplied by the urine volume can reflect the 24 h UTR.