Interpreting Urine Albumin: Who Lives? Who Dies?

Robert W. Morrow, MD; Lynda A. Szczech, MD, MSCE


August 14, 2012

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Robert W. Morrow, MD: Hi, welcome. This is Dr. Bob Morrow. We are doing another recording of a new type of video roundtable, "Primary Care Goes to Urinetown." I am a family physician in the Bronx and Clinical Associate Professor in the Department of Family and Social Medicine at the Albert Einstein College of Medicine. We are here with Dr. Lynda Szczech.

I have a question that has been bothering me and hopefully has been bothering you. I hope we get some good answers. Lynda?

Lynda A. Szczech, MD, MSCE: Hi. My name is Lynda Szczech. I am a nephrologist practicing in Durham, North Carolina, and I am proud to be President of the National Kidney Foundation.

During our previous chat, I gave a plug for the National Kidney Foundation's Website, I did that because our clinical practice guidelines are posted there. As I said before, they are a bit dry, but chock-full of information. If you need more information after listening to this discussion, please feel free to go to those clinical practice guidelines. I hope they will be of help.

Dr. Morrow: Thank you. Today, we are going to spend a few minutes discussing urinary microalbumin, a very wet subject, and hopefully interesting enough for everybody.

We don't dip our fingers into tests anymore, but the issue came up many years ago, when someone asked me at a quality improvement committee meeting, "Why can't the doctors just test urine microalbumin?" I said that maybe we should tell them that they should do it, and maybe we should tell them why.

The big question here is how often we should do this. Is this something that should substitute for a more quantitative test for total albumin? Is this something that they are going to stop doing at some point? Is it sensible? Is it predictive? Lynda, those are your questions.

Dr. Szczech: All right. Why do it, and who do we do it on? The biggest problem with urine albumin is interpretability, because it seems very complicated initially -- mostly because when you get a urine albumin value and a urine creatinine value, and you divide the 2 to get the ratio, they are in different units. That is kind of weird -- milligrams of albumin per gram of creatinine. You have to watch out for that, and if you get confused, reach out to people. Everybody gets confused by that.

In terms of interpretability, what is the threshold? About 5 years ago, we thought that less than 30 mg/day was great -- if you have 29 mg of albumin per 24 hours, you are going to live forever, but if you are at 31 mg/day, oh my gosh, make sure that your will is in order. Actually, that threshold of 30 mg/day is not set in stone like we thought. It turns out that between 0-5 (the lower limits of detection) and 30, there is a linear relationship with mortality.

That brings us to 2 points. First, regardless of where you are, if you can detect a number that is greater than 10, you want to get that number lower. In fact, if I had a urine albumin level of 15, 20, or 25 mg/day, I would want to get it lower. All of the physicians listening to us, as well as other providers, should want to know what their urine albumin is, because it correlates with mortality. It kind of correlates with loss of kidney function, but when you find it, the kidney disease is caught so early that the number of people who will live long enough to develop progressive kidney disease is relatively small.

That's the pearl: Urine albumin correlates with mortality. It is your way to look at vascular health. Just like when you see proliferative retinopathy in the eyes of a patient with diabetes and know that the rest of the blood vessels probably don't look so good, if you see urine albumin, you should think to yourself that the rest of the blood vessels probably don't look so great and focus on cardiovascular risk factor reduction.

No one ever got hurt by peeing in a cup. It's cheap, easy, and it gives you an even better sense of who is going to live to see another birthday than does high-density lipoprotein (HDL) and low-density-lipoprotein (LDL) cholesterol.

Dr. Morrow: You are looking at this as a global measure, and you would then address vascular risk rather than strictly give an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker. This is more a question of total cardiovascular health.

Dr. Szczech: Right.

Dr. Morrow: What is the difference between urine microalbumin and albumin?

Dr. Szczech: Nothing. Microalbumin and albumin are the same thing.

Dr. Morrow: Excellent. I think that has been very helpful. Thank you. We will be coming back with an even more challenging subject. Thanks for coming to listen. Goodbye.


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