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ALBUMIN/CREATININE RATIO (ACR)

Definition

The Albumin/Creatinine ratio (ACR) test result is the ratio of measured albumin (a protein) and creatinine (a metabolism by-product) in the urine that has been excreted from the body, at the time of the test (spot sample). Creatinine is produced by the body at a constant rate, depending on muscle mass, and is removed by the kidneys. If the kidneys do not have adequate filtering capabilities (impaired kidney function), creatinine levels rise in the body and albumin can leak into the urine, and this is referred to as albuminuria.¹ The severity of ACR levels, or albuminuria, is indicated as microalbuminuria and macroalbuminuria. which refers to impaired kidney function, and normoalbuminuria referring to normal ACR levels (adequate kidney function).²

Population

Albumin and creatinine results were obtained for persons aged 18 years and over, who participated in the National Aboriginal and Torres Strait Islander Health Measures Survey (NATSIHMS) and who provided a urine sample. Fasting was not required for this test.

Methodology

A urine sample was collected from participants and urinary albumin and creatinine levels were measured at the Douglass Hanly Moir (DHM) laboratory.

In the NATSIHMS, cut off reference values for albuminuria were sourced from the chronic disease position statement put out by the Medical Journal of Australia and the Chronic Kidney Disease (CKD) management guidelines by Kidney Health Australia.^2,3 These guidelines are based on epidemiological data and publications of major clinical trials.

In the NATSIHMS, the following definitions were used for albuminuria (ACR levels):

	ACR levels for females (mg/mmol)	ACR levels for males (mg/mmol)
Normoalbuminuria (Normal)	<2.5	<3.5
Microalbuminuria	2.5 to <25.0	3.5 to <35.0
Microalbuminuria	≥25.0	≥35.0

• ACR test results do not confirm a specific diagnosis without consultation with a health professional.
• There are a number of different test methods for measuring urine albumin and creatinine, which may produce different results. The data from this topic should therefore be used with caution when comparing ACR results from other studies using a different test method or equation.
• Factors such as urinary tract infections, high protein diet intake or heavy exercise within 24 hrs are known to affect ACR results (other than chronic kidney disease).³ As a result, the data should be interpreted with care.