Am Fam Physician. 1999;59(11):3243
Annual screening for evidence of microalbuminuria is recommended in patients with diabetes. The presence of microalbuminuria in patients with type 1 diabetes (formerly known as insulin-dependent diabetes) is associated with a three- to eightfold increase in the relative risk of cardiovascular disease. For patients with type 2 diabetes (formerly known as non–insulin-dependent diabetes), the relative risk of cardiovascular disease increases by two to four times when microalbuminuria is present. A challenge to periodic screening for microalbuminuria is that 24-hour urine collections are cumbersome, possibly contributing to noncompliance. Bakker compared the reliability of 24-hour collection versus the urinary albumin concentration and the albumin-to-creatinine ratio in detecting microalbuminuria.
A total of 2,394 consecutive urine samples from 1,171 men and 1,223 women with diabetes were evaluated over a period of two-and-one-half years. Standard methods were used to determine the total albumin excretion rate, the urinary albumin concentration and the albumin-to-creatinine ratio. On the basis of the albumin excretion rate, the frequency of microalbuminuria in this population was 36.6 percent in the men and 27.9 percent in the women. The frequency of microalbuminuria increased steadily after the age of 50 years.
The correlation between the albumin excretion rate and the albumin concentration was considered “acceptable” and did not show sex-related differences. However, there was a closer correlation between 24-hour collection values and the albumin-to-creatinine ratio. The correlation improved for men and women when they were considered separately. An albumin excretion rate of 20 μg per minute corresponded to an albumin-to-creatinine ratio of 1.98 g per mol for men and 2.81 g per mol for women. An albumin excretion rate of 200 μg per minute corresponded with an albumin-to-creatinine ratio of 19 g per mol for men and 28 g per mol for women.
The author concludes that the albumin-to-creatinine ratio may be used in place of the more cumbersome 24-hour urine collection for the detection of microalbminuria. The sensitivity and specificity of the albumin-to-creatinine ratio were 94 percent and 92 percent, respectively, at 2.5 g per mol for women, and 94 percent and 93 percent, respectively, at 1.8 g per mol for men. In contrast to the urinary albumin concentration, however, the albumin-to-creatinine ratio requires both sex- and age-specific discriminator values.