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  1. Dr. Jordan Weinstein
  2. Verified UKidney Expert
  3. General Nephrology Questions
  4. Friday, 31 October 2014
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Please elaborate on the meaning of this test and what it represents
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The development of a microalbuminuria assay remains an important development in nephrology, especially in the management of early kidney disease. However, this relatively straightforward test does have some caveats that cause confusion. I hope to clarify some of this below. The most commonly used test to detect proteinuria is a conventional urinalysis dipstick. This test is a colorimetric assay that measures urinary concentration of albumin. The fact that it measures concentration is an important issue and drawback. If one was looking to quantify a patient’s albumin excretion then using a test that measures concentration is suboptimal because for the same total amount excreted, the lab will predict different results depending on the degree of urinary concentration. Since patients will have a variable fluid intake within and between days, there must be a standardized way to detect proteinuria which is independent of urinary volume. The albumin to creatinine ratio is a clever innovation which measures the exact concentration of albumin in the urine and divides it by the concentration of creatinine in that same urine. The effect of this is to correct for the degree of urinary dilution or concentration that might be present. Since the creatinine is measured in the same sample of urine as the albumin, the the effect of concentration or dilution will be eliminated. The end result is an equation which does not depend on volume, namely it is reported as milligram albumin divided by mol creatinine (mg/ mmol). Since volume does not appear, it has no bearing on the calculation. Therefore, highly concentrated specimens of urine will not overestimate albumin excretion when using this formula since the degree of creatinine concentration will be identical and normalize the result. Furthermore, the lower limit of detection of albumin concentration is more sensitive than conventional dipsticks and so therefore, the albumin:creatinine ratio is both more sensitive for small protein excretion and more accurate for predicting true albumin excretion rates. Some labs will report the albumin concentration (not the ratio) and this creates additional confusion. Take for example the following scenario; if a patient has a urinary concentration of albumin detected in the lab measuring 15 mg/L, this might be interpreted as a slightly elevated albumin concentration. However if the accompanying creatinine concentration is 12 mmol per liter then the ratio is 1.1 mg/mmol, below the normal limit of the albumin to creatinine ratio ( One can also use the albumin to creatinine ratio to predict 24 hour protein excretions, since protein excretion is relatively constant over a 24 hr period and creatinine excretion can be estimated at 10 mmol/day for woman and 12 mmmol/day for men. In the example above, if a woman had an ACR of 1.1 mg/mmol, then her 24 hour albumin excretion could be estimated at 10 x 1.1 or 11 mmol/day. The advantages of the albumin to creatinine ratio are:
[list] [*] It can be used to detect very low levels of albumin excretion [*] It is not confounded by urinary concentration or dilution [*] It can be used to estimate one's 24-hour albumin excretion. [/list]
In many cases this simple test obviates the need to measure 24 hour protein quantities which are cumbersome and often inaccurate. The one caveat of replacing the ACR ratio for 24 hour urine protein is that this simple assay only detects albumin and not other proteins such as Bence Jones proteins, for example. In the case of other urinary proteins, one can measure a protein to creatinine ratio and this will measure all proteins, including albumin and others. Once Bence Jones proteinuria was ruled out, one could continue monitoring for the presence of albumin as a reliable indicator or proteinuric kidney disease.
  1. more than a month ago
  2. General Nephrology Questions
  3. # 1
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You can read article at bcmj
  1. more than a month ago
  2. General Nephrology Questions
  3. # 2
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thnks sir
  1. more than a month ago
  2. General Nephrology Questions
  3. # 3
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Attached is my albumin/creatinine ratio which is 12. may I know the result if its normal or not?

Thank you
Accepted Answer Pending Moderation
Hello,

The albumin to creatinine ratio is normal. Please don't post items with your name visible. I have removed this report from our server.

Dr. Jordan Weinstein
Accepted Answer Pending Moderation
Hello Doctor, could you help me with understanding my results?
Thanks, Matt N.

Creatinine: Random urine In mg/dl units 200.7 (1 day ago) 333.6 (1 year ago)

Albumin: Random urine In mg/dl units 16.7 (1 day ago) 8.9 (1 year ago)

Albumin/Creatinine Ratio: In mg/dl units 83 (1 day ago) 27 (1 year ago)
Accepted Answer Pending Moderation
Hello,

Those units and that calculation do not seem to work out. Can you upload your latest laboratory results with your name and identifying information blocked out?

Dr. Jordan Weinstein
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