Is the albumin (Albumin) to creatinine (Creatinine) ratio the same as the microalbumin (Microalbumin) to creatinine (Creatinine) ratio?

From the Guidelines

The albumin to creatinine ratio (ACR) and the microalbumin to creatinine ratio (MACR) are essentially the same test, just with different naming conventions, as both measure the amount of albumin in the urine compared to creatinine to assess kidney function. The term "microalbumin" specifically refers to small amounts of albumin in urine that are below the detection threshold of standard dipstick tests but can indicate early kidney damage. These tests are typically reported in mg/g or mg/mmol units and are used to screen for and monitor diabetic nephropathy, hypertensive kidney damage, and other forms of kidney disease.

Key Points

• Normal values are generally below 30 mg/g creatinine, with 30-300 mg/g indicating moderately increased albuminuria (formerly called microalbuminuria) and values above 300 mg/g indicating severely increased albuminuria, as defined in the most recent guidelines 1.
• The test requires only a random urine sample rather than a 24-hour collection, making it convenient for regular monitoring of kidney function in at-risk patients, as recommended by the American Diabetes Association 1.
• The use of the term "microalbuminuria" is no longer recommended, and instead, the term "moderately increased albuminuria" should be used to describe albuminuria in the range of 30-300 mg/g, as suggested by the Kidney Disease: Improving Global Outcomes (KDIGO) clinical practice guideline 1.

Monitoring and Management

• The frequency of monitoring should depend on the severity of CKD and the risk for progression, with factors such as cause of CKD, level of GFR, level of albuminuria, and presence of comorbidities taken into account, as outlined in the KDIGO guideline 1.
• An approach involving an assessment of change in eGFR category confirmed by a minimal percentage of change in eGFR (25% or greater) is recommended to define progression, as suggested by the KDIGO guideline 1.
• Increasing levels of albuminuria suggest progression and have been shown to be associated with increased risk for adverse outcomes, as reported in the study by 1.

From the Research

Definition and Measurement

• The albumin to creatinine ratio (ACR) and microalbumin to creatinine ratio are related but distinct measures, as they both assess the level of albumin in the urine relative to creatinine 2.
• Microalbumin refers to a specific range of albumin levels in the urine, typically between 30-300 mg/g creatinine 3.
• The ACR is a more general term that encompasses the measurement of albumin levels in the urine relative to creatinine, regardless of the specific range 4.

Comparison of Ratios

• Studies have shown that the ACR and microalbumin to creatinine ratio are correlated, but not identical [(2,5)].
• The relationship between ACR and microalbumin to creatinine ratio can be influenced by various factors, such as the analytical methods used to measure albumin and creatinine 6.
• Equations have been developed to estimate ACR from protein-to-creatinine ratio (PCR), which can be useful in situations where only PCR is available 4.

Clinical Significance

• Both ACR and microalbumin to creatinine ratio are used to assess kidney function and detect early signs of kidney disease [(2,3)].
• The severity of albuminuria, as measured by ACR or microalbumin to creatinine ratio, can stratify the risk of progressive chronic kidney disease 3.
• Accurate measurement of ACR or microalbumin to creatinine ratio is crucial for monitoring kidney disease progression and making informed clinical decisions 6.