Thread by @kidney_boy

Internists know that eGFRs can not be used in AKI, that the formula requires the patient’s being in steady state. But fewer internists (and fellows) know that also applies to the protein to creatinine ratio (PCR). (1/10)

Over and over again, I see protein to creatinine ratios ordered in the midst of AKI to “quantify the proteinuria”

The protein to creatinine ratio depends on the patient excreting their daily creatinine load and patients in the midst of AKI (either worsening or improving) do not.

When the creatinine is worsening, the urinary creatinine is less than the daily creatinine load. This decreases the denominator and can inflate the PCR. In my experience this is particularly evident in cardiorenal syndrome type 1. (3/10)

This can throw off the diagnostician as they start sniffing around for a non-existent glomerular disease in purely hemodynamic cardiorenal syndrome. (4/10)

Even more concearning would be looking at the PCR in a patient with recovering kidney function. Here, presumably, the increased urinary creatinine would systematically underestimate proteinuria and allow an actual GN to go unrecognized. (5/10)

Some people state that as long as we recognize the error, and understand the limitations of the PCR in AKI it is okay to order it, “We will just discount the result.”

This also worries me. Sure, today we discount the result, but... (6/10)

...what happens two years from now when some one is perusing old labs and tries to interpret the PCR without the clinical context. They would have no idea the elevated PCR is an artifact of AKI. (7/10)

One of the recurring diagnostic dilemmas in nephrology is when is the proteinuria due to diabetes and when is it due to a primary (and treatable) glomerular nephritis. One of the core peices of data is looking at the acquity of the rise in proteinuria. (8/10)

I worry that an old artifactual elevated PCR could make an acute GN masquerade as a long standing nephropathy and result in people missing treatable disease. (9/10)

Let’s stop ordering the PCR in AKI. (10/10)

Great article from a few years ago about this:

ncbi.nlm.nih.gov/pmc/articles/P…