Hello, I’m Dr. Hocheol Shin, or “Dr. Shin.” I study feline kidney health and aging at Greycoat Research.

I earned my Ph.D. studying cancer and immunology, and I’m now building on that experience to explore how we can help cats stay healthier for longer.

In “Reading Papers with Dr. Shin,” we’ll explore research related to feline health together. We’ll look a little deeper into how things work, what the studies actually found, and what those findings might mean for our cats. I’ll explain any unfamiliar terms as we go.

Ready to open today’s paper with Lulu?

Three-Sentence Summary

1. When researchers tested stored blood samples from 21 cats with chronic kidney disease, they observed elevated SDMA before elevated creatinine in 17 cats.

2. The reported average lead time in those 17 cats was 17 months, but this does not mean the test detects kidney disease 17 months earlier in every cat.

3. When interpreting markers and studying management approaches at Greycoat Research, it is important to consider changes within the same cat and what they mean, rather than relying on a single number.

Introduction: What Is the Point of Another Kidney Test?

On a cat’s kidney blood panel, you may see SDMA listed alongside creatinine. If both help assess kidney function, why use two tests?

The fact that a test is newer is not enough. We need to know whether it adds information that the existing test might miss.

Today’s paper asks a question about timing: “Can a change in SDMA appear before creatinine crosses its threshold?”

To investigate, the researchers went back to stored blood samples. They were looking not just at one lab report, but at the history of the same cats.

Background: Measuring Function versus Estimating It from a Concentration

The rate at which the kidneys filter substances from the blood is called the glomerular filtration rate, or GFR.

Creatinine and SDMA concentrations are not direct measurements of GFR. These substances are produced in the body and cleared through the kidneys. Measuring how much remains in the blood gives us an indirect way to assess kidney function.

We should also distinguish a test’s reference interval from the function it helps us assess. The interval provides a basis for interpreting a result. It does not mean that every cat within that interval has identical kidney function.

In this study, the researchers compared when each marker rose above its reference interval. That is the basis for the word “earlier” in the findings we’re about to discuss.

The Study: Stored Blood Preserved a Record of the Past

Hall and colleagues published this study in the Journal of Veterinary Internal Medicine in 2014.

It included 21 cats with chronic kidney disease and 21 healthy older cats selected from the same research population. The researchers used stored historical blood samples and clinical records. GFR measurements were also available for some cats, allowing comparison with the two markers.

Both SDMA and creatinine were associated with GFR. In 17 of the 21 cats with CKD, elevated SDMA was observed before elevated creatinine.

That is what makes the paper interesting. It showed that one marker could reveal a change before the established marker crossed its threshold.

Reading the Results: The Records Matter as Much as the New Test

SDMA itself is not the only thing that catches my attention. It also matters that historical blood samples were available.

Comparing only current results would mainly let us ask, “How high is each marker?” Stored samples made another question possible: “When did the change first become visible?” The researchers could ask a different kind of question.

Following the same cat’s measurements over time gives us information that a one-time comparison between different cats cannot provide. We can look not just at whether today’s result falls within the reference interval, but at the pattern leading up to it.

That is why I do not read this paper simply as a contest over whether SDMA is “better” than creatinine. The more useful question is what we learn by considering both markers alongside the cat’s history.

A Point to Keep in Mind: Read “17 Months Earlier” Carefully

The paper reported an average lead time of 17 months in the 17 cats with earlier SDMA elevations. It is an eye-catching number, but the circumstances behind the calculation matter.

Some cats never developed creatinine values above the threshold during observation. For those cases, the calculations used periods extending to death or the end of observation, among other endpoints. For the remaining four cats, earlier stored samples were not available to assess SDMA.

This was also not a study that followed every cat from the outset at fixed intervals. How far back the researchers could look depended on which historical samples remained available.

So the conclusion is not, “An SDMA test detects kidney disease 17 months earlier in every cat.” The finding to take away is the possibility of observing a change in another marker before creatinine crosses its threshold, not a promise of an exact number of months.

Personal Thoughts: What Happens After We Notice the Change?

Being able to recognize a change earlier is an important possibility. As a researcher, though, I am also interested in what comes next.

Which additional tests should follow? What evidence would justify starting a particular management approach? And does that management actually change the cat’s condition or longer-term outcomes?

A test detecting a change and care guided by that test providing a benefit are related, but separate, questions. Each needs an answer.

I think that distinction should also guide how we study management approaches at Greycoat Research. We should not stop at saying that a marker changed. We need to examine what happened over time in the same cat and what that change means. Today’s paper did not establish the efficacy of a particular management approach or product.

SDMA is not a number that erases creatinine. It is another piece of information about the cat. Add the cat’s history, and the questions become more useful.

Next time, we’ll place weight records beside the blood results. Were changes in body weight already appearing before kidney disease was diagnosed?

The findings discussed in this article reflect associations, mechanisms, and early translational evidence rather than confirmed efficacy in cats with kidney disease. Please consult a veterinarian before starting any supplementation protocol.

References

1. Hall JA, Yerramilli M, Obare E, Yerramilli M, Jewell DE. Comparison of Serum Concentrations of Symmetric Dimethylarginine and Creatinine as Kidney Function Biomarkers in Cats With Chronic Kidney Disease. Journal of Veterinary Internal Medicine. 2014;28:1676–1683.

About the Author

Hocheol Shin, Ph.D. Greycoat Research

B.S./M.S./Ph.D. in Biological Sciences, KAIST (Korea Advanced Institute of Science and Technology)

Research background in cancer immunology, tumor microenvironment, and translational oncology. Currently engaged in companion animal health and longevity research.

[Educational Disclaimer]

This article is for educational purposes only and is not a substitute for professional veterinary advice, diagnosis, or treatment. It is not intended to diagnose, treat, cure, or prevent any disease.

Please consult your veterinarian before making changes to your cat’s diet, supplements, or care routine.