From the Guidelines
According to KDIGO, a normal albumin-to-creatinine ratio (ACR) is less than 30 mg/g (or less than 3 mg/mmol) 1. This measurement is used to assess kidney function by quantifying the amount of albumin protein excreted in the urine relative to creatinine. An ACR below this threshold indicates normal kidney function with no significant albumin leakage into the urine. Values between 30-300 mg/g (3-30 mg/mmol) indicate moderately increased albuminuria, while values above 300 mg/g (>30 mg/mmol) represent severely increased albuminuria. Regular ACR monitoring is important for early detection of kidney disease, especially in patients with diabetes, hypertension, or other risk factors for kidney damage 1. The test is preferred over a simple urine dipstick because it provides a more accurate quantification of albumin excretion and accounts for variations in urine concentration. Some key points to consider when interpreting ACR results include:
- ACR is a continuous marker for cardiovascular event risk at all levels of kidney function 1
- High urinary albumin excretion is defined as ≥30 mg/g Cr 1
- Two of three specimens of UACR collected within a 3- to 6-month period should be abnormal before considering a patient to have high or very high albuminuria 1
- Exercise, infection, fever, congestive heart failure, marked hyperglycemia, menstruation, and marked hypertension may elevate UACR independently of kidney damage 1
From the Research
Definition of Normal ACR according to KDIGO
- The Kidney Disease: Improving Global Outcomes (KDIGO) defines the severity of chronic kidney disease based on glomerular filtration rate (GFR) and albuminuria (ACR) 2.
- According to the study, the KDIGO A1-A2-A3 categories are used to stage ACR, but the exact values for a normal ACR are not explicitly stated in the provided evidence.
ACR Categories and Corresponding Values
- A study published in the Journal of the American Heart Association in 2016 found that a urine albumin:creatinine ratio (UACR) below 30 mg/g is a predictor of incident hypertension and cardiovascular mortality 3.
- However, it is essential to note that this value is not explicitly stated as the normal ACR according to KDIGO in the provided evidence.
KDIGO Staging of ACR
- The KDIGO staging of ACR is mentioned in the study published in Clinical chemistry and laboratory medicine in 2022, which investigated the performance of equations to estimate ACR from protein to creatinine ratio 2.
- The study reports that the proportion of measured ACR (mACR) in the A1 category was 65.6%/64.2%, A2 was 25.5%/25.5%, and A3 was 8.8%/10.3% (Method R/A, respectively), but the exact values for each category are not provided.
In summary, while the provided evidence discusses the importance of ACR in assessing chronic kidney disease and its relationship with cardiovascular outcomes, it does not explicitly state the normal ACR value according to KDIGO. However, a UACR below 30 mg/g is mentioned as a predictor of incident hypertension and cardiovascular mortality in one of the studies 3.