糖尿病外来診療におけるアルブミン/クレアチニン比の臨床的評価 第一報

Abstract

For the early diagnosis of diabetic nephropathy, it is best to use the albumin excretion rate (AER). However, it is a complicated test to perform in the outpatient setting, and it is sometimes affected by inaccurate urine collection. Therefore, we have used the albumin/creatinine ratio, which is measured simply with randomly collected urine, for evaluation of microalbuminuria and found it to be of equal diagnostic value to the AER. The AER, albumin/creatinine ratio, and creatinine excretion rate were measured in 86 patients with NIDDN who were negative for proteinuria. Urine was obtained after bed rest and in the outpatients department (without rest). 1) The reproducibility of time-restricted urine sampling was investigated using the rate of creatinine excretion. The mean coefficient of variation was found to be 42%, and inaccurate urine sampling appeared to cause variation in the AER. 2) The AER and albumin/creatinine ratio obtained in the outpatient setting were higher than those after bed rest, and urine collection at the time of outpatient examination was considered to be more useful than that after bed rest. To check variations in urine collection at the time of outpatient examination, the albumin/creatinine ratio in random urine samples was superior on the basis of the correlation coefficients to urine obtained after bed rest. 3) The urinary creatinine excretion rate showed a significant sex difference (males: 0.823 +/- 0.152 mg/g. creat., females: 0.577 +/- 0.194 mg/g. creat) (p less than 0.001), but there was no significant difference for BMI and age. The relationship between each level of microalbuminuria and the creatinine excretion rate did not change significantly. 4) The following formula was used to calculate the albumin/creatinine ratio corresponding to the AER. Albumin/creatinine ratio formula; (see text) An AER of 30 micrograms/min thus corresponds to an albumin/creatinine ratio of 36 mg/g. creat. for males and 51 mg/g. creat. for females. 5) The percentage of positive results for microalbuminuria in patients with NIDDM showed that the albumin/creatinine ratio and the AER were equal as diagnostic criteria, when the sex difference was taken into consideration. Thus, the albumin/creatinine ratio is equal to the AER for evaluation of microalbuminuria, and it is a simple and convenient test to use in daily clinical practice.