Application of urinary albuminuria at different time in the monitoring of early impairment in kidney of diabetes mellitus

Abstract

Objective To investigate the urinary albumin excretion of the diabetes patients and application value in the monitoring of early impairment in kidney. Methods The random urine samples from diabetes patients and controls within three days were collectod. The changes of urinary albumin excretion within day and between days were analyzed. 24-hour urine albumin was used as a standard to evaluate early kidney damage. The correlations between results of random urine albumin at the different time points and different periods were comparod. The sensitivity and specificity of random urine albumin at the different time points and different periods was evaluated and compared to deduce the best diagnostic porformance of the random urine albumin. Results There are greater variations of the levels of urinary albumin of patients with diabetes and control. After the correction with urine creatinine and urine volume the variations can be reduced (CV:49%±23% and 64%±30%). Urinary albumin excretion rate change rhythmically within the 24 h in healthy and diabetes patients. We found the best correlation between overnight ratio of urinary concentrations of albumin and creatinine (ACR) and 24-hour urinary albumin (R2 = 0.976). It was superior to urina sanguinis (R2 = 0.900), postprandial urine (R2 = 0.584) and random urine (R2 =0.791). When 24 h urinary albumin was taken as the standard, receiver operating characteristic (ROC) curve analysis showed there was significant difference between male and female(male 12.8 μg/mg urine creatinine vs female 27.0 μg/mg urine creatinine),and the the cut-off value of ACR was 27.7μg/mg urine creatinine. When the smallest available negative likelihood ratio (0.011) and the greatest positive likelihood ratio (481.000) were obtained,the concentration of 13.0 μg/mg creatinine and 87.4 μg/mg creatinine were set as the cut-off value of ACR. Conclusions The correction with urinary creatinine can reduce the variation between-days compared with urine volume, but still can not completely eliminate the variability. The ACR of overnight urine has the best correlation with the 24 h urinary albumin and can replace 24 h urinary albumin. Random urine as the most convenient collecting urine samples can also replace 24-hour urinary albumin, but the gender discrepancy need to be considered. When the concentration of 13.0 μg/mg and 87.4 μg/mg was set as a random ACR exclusion value and the confirmative value, it can basically rule out and confirm the existence of microalbuminuria. Key words: Diabetic nephropathies; Albuminuria; Albumins; Urinalysis; Creatinine