IDEXX Laboratories is in the process of rolling out a new test that they say “detects kidney disease in cats and dogs months or years earlier than standard screening technologies.” Is the SDMA (symmetric dimethylarginine) test really the breakthrough that it is advertised to be?
First some background…
The “standard screening technologies” to which IDEXX refers are the blood chemistry parameters blood urea nitrogen (BUN) and creatinine and urine specific gravity. When a veterinarian suspects that a dog or cat might have kidney disease, he or she will order blood tests and a urinalysis that include these parameters. If BUN and/or creatinine levels are found to be high and the urine specific gravity is low, a diagnosis of kidney disease can be made. The problem is that urine specific gravity only starts to fall once around two-thirds of kidney function has been lost, and BUN and creatinine rise when more than three-quarters of kidney function is gone. Relying on these findings means that we are diagnosing chronic kidney disease very late in the game.
According to IDEXX:
The new SDMA test changes that. In a recent clinical study, Oregon State University researchers showed SDMA identified disease much earlier in the disease progression, when the kidney had suffered far less damage that results in permanent loss of function — up to four years earlier in at least one animal. On average, SDMA detected kidney disease when only 40% of function had been lost and, in some cases, 25% of function.
For now, we’ll have to take their word on that. All the research I’ve seen on the use of SDMA in dogs and cats (including the study referenced above) has been sponsored, at least in part, by IDEXX. But even if independent research eventually corroborates these findings, my real question is, “will earlier detection prove to be all that helpful?”
Standard treatment for chronic kidney disease is essentially supportive and symptomatic. Fluid therapy (intravenous, subcutaneous, or oral) helps correct and prevent dehydration and lower BUN, creatinine, and phosphorous levels. A combination of medications and nutritional supplements can also be given to treat problems that arise secondary to chronic kidney disease such as high phosphorous and low potassium levels, high blood pressure, urinary protein loss, gastrointestinal ulcers, and anemia, but none of these interventions are preventative in nature and they should only be instituted when abnormalities show up on standard diagnostic testing.
The only recommendations I can foresee making based on an elevated SDMA test when everything else appears to be normal are –
- Ensure adequate water intake by switching to canned food if at all possible (especially for cats) and/or emphasizing the need to have fresh water readily available at all times.
- Feed a diet that meets but does not greatly exceed the dog or cat’s need for protein and is made from high quality protein sources.
- Avoid anything that could worsen kidney function (e.g., low blood pressure during anesthesia and toxins that are known to damage the kidneys)
- Closely monitor for a worsening of kidney function that might indicate more treatment is needed.
… but don’t those recommendations really apply to all dogs and cats regardless of the results of an SDMA test?
I certainly hope this new test results in increased longevity and improved quality of life for dogs and cats with kidney disease, but in truth, only time and independent research will ultimately reveal how useful it is.
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