From the Guidelines
The albumin:creatinine (A:C) ratio is a crucial diagnostic tool for detecting and monitoring kidney damage, particularly in high-risk populations such as those with diabetes or hypertension, as it provides a reliable assessment of albumin excretion and accounts for variations in urine concentration. The A:C ratio is preferred over a simple urine albumin measurement because it offers a more accurate indication of kidney health. According to the most recent guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus 1, the A:C ratio is the best method to predict renal events in people with type 2 diabetes.
Key Points About the A:C Ratio
- Normal A:C ratio values are typically below 30 mg/g, with 30-300 mg/g indicating microalbuminuria (early kidney damage) and values above 300 mg/g suggesting macroalbuminuria (more significant kidney damage) 1.
- The test is convenient as it requires only a spot urine sample rather than a 24-hour collection.
- Regular monitoring of the A:C ratio allows healthcare providers to assess the progression of kidney disease and the effectiveness of treatments aimed at preserving kidney function.
- The presence of albumin in urine indicates damage to the glomerular filtration barrier in the kidneys, which normally prevents proteins from passing into the urine, making this an excellent biomarker for kidney health assessment.
Clinical Application
The A:C ratio is useful for detection, differential diagnosis, prognosis, and treatment of chronic kidney disease, as highlighted in the national kidney foundation practice guidelines for chronic kidney disease 1. It is also recommended for continued monitoring of urinary albumin–to–creatinine ratio in patients with albuminuria treated with an ACE inhibitor or an angiotensin receptor blocker to assess the response to treatment and progression of diabetic kidney disease 1.
Best Practices for Measurement
To minimize variability, all collections should be at the same time of day and the person should not have ingested food for at least 2 h 1. Albumin is stable in untreated urine stored at 4 °C or -20 °C for at least a week, and neither centrifugation nor filtration appears necessary before storage at -20 °C or -80 °C 1.
Conclusion is not needed as per the guidelines, the above information is sufficient to answer the question.
From the Research
Purpose of Albumin:Creatinine Ratio
The albumin:creatinine ratio (A:C) is used in clinical practice for several purposes:
- To screen for microalbuminuria, which is an established risk factor for renal disease progression in type 1 diabetes and a marker of endothelial dysfunction 2
- To monitor kidney function in patients with diabetes and hypertension 3
- As a predictor of albumin excretion rates greater than 30 micrograms/min, which is a strong predictor of future clinical diabetic nephropathy 4
- To assess the risk of cardiovascular disease, as microalbuminuria is associated with higher blood pressures, increased serum total cholesterol, and reduced serum high-density lipoprotein cholesterol 2
Advantages of Albumin:Creatinine Ratio
The A:C ratio has several advantages over other methods of screening for kidney disease:
- It is more sensitive than urine dipstick testing, which does not become positive until protein excretion exceeds 300-500 mg/day 2
- It provides a quantitative measure of albumin excretion, which can be used to monitor disease progression and response to treatment 3
- It is a useful initial screening test for microalbuminuria, with high sensitivity and specificity 4
- It is similar to the protein-creatinine ratio (PCR) in its associations with common complications of chronic kidney disease (CKD) 5
Clinical Applications
The A:C ratio has several clinical applications:
- It is recommended as the preferred screening strategy for all diabetic patients 2
- It is used to monitor the effectiveness of antihypertensive therapy in patients with diabetes and hypertension 2
- It is used to assess the risk of cardiovascular disease in patients with diabetes and hypertension 2
- It is used to monitor kidney function in patients with CKD, and to adjust treatment accordingly 5