What are the developments in albuminuria (protein in the urine) testing?

From the Guidelines

Albuminuria testing should be performed annually in adults with diabetes using the morning spot urine albumin-to-creatinine ratio (uACR) as the gold standard, with values above 30 mg/g indicating albuminuria. This recommendation is based on the most recent and highest quality study, which emphasizes the importance of regular testing in high-risk populations, such as those with diabetes or hypertension 1. The uACR test has replaced older qualitative dipstick methods due to its greater accuracy and reliability, and it requires a spot urine sample, ideally collected as the first morning void, to account for urine concentration variations.

Key points to consider in albuminuria testing include:

• The use of first morning void urine sample for measurement of albumin-to-creatinine ratio, as it minimizes variability in test results 1
• The importance of confirming abnormal results with at least two additional tests over a 3-6 month period, as transient albuminuria can occur due to fever, exercise, or urinary tract infections 1
• The need for regular testing in patients with diabetes, hypertension, or family history of kidney disease, with annual screening recommended for these high-risk populations 1
• The use of semiquantitative uACR dipsticks as an alternative to quantitative tests, which can be used to detect early kidney disease and assess cardiovascular risk when quantitative tests are not available 1

In terms of analytical performance, the goals for urine albumin measurement should be between-day precision ≤6%, bias ≤7% to 13%, and total allowable error ≤24% to 30% 1. Additionally, timed collection for urine albumin should be done only in research settings and should not be used to guide clinical practice 1. Overall, the uACR test is a reliable and accurate method for detecting albuminuria, and regular testing is essential for early detection and management of kidney disease in high-risk populations.

From the Research

Development in Albuminuria Testing

• Albuminuria is a predictive marker for the early detection of renal disease and the identification of patients at high risk of developing complications of diabetes and hypertension 2.
• The management of albuminuria in patients with hypertension and diabetes mellitus typically involves inhibitors of the renin-angiotensin system, which have been shown to be more effective than calcium channel blockers in decreasing albuminuria 3.
• Point-of-care devices, such as the Bayer Clinitek 50, have been developed for the semi-quantitative measurement of albumin and creatinine and calculation of albumin:creatinine ratio (ACR), providing useful clinical information regarding microalbuminuria status 4.
• Diagnostic performance of random urine samples using albumin concentration vs ratio of albumin to creatinine for microalbuminuria screening in patients with diabetes mellitus has been compared, with results showing no differences in sensitivity, specificity, or diagnostic odds ratios between the two methods 5.
• Recent studies have also investigated the association between microscopic hematuria and albuminuria in patients with chronic kidney disease caused by diabetes and hypertension, finding a significant association between the two conditions 6.

Testing Methods

• Inhibitors of the renin-angiotensin system are recommended for the management of albuminuria in patients with hypertension and diabetes mellitus 3.
• Point-of-care devices, such as the Bayer Clinitek 50, can provide immediate clinical information regarding microalbuminuria status 4.
• Albumin concentration and ratio of albumin to creatinine are both effective methods for microalbuminuria screening in patients with diabetes mellitus 5.
• Urinary albumin-creatinine ratio is a commonly used measure of albuminuria, with macroalbuminuria defined as a ratio >300 mg/g 6.

Clinical Applications

• Albuminuria testing is important for the early detection of renal disease and the identification of patients at high risk of developing complications of diabetes and hypertension 2.
• Point-of-care devices can provide useful clinical information regarding microalbuminuria status, allowing for timely intervention and management 4.
• The association between microscopic hematuria and albuminuria in patients with chronic kidney disease caused by diabetes and hypertension highlights the importance of considering both conditions in clinical practice 6.