Studies have shown that lipemia and icterus do not affect the IDEXX SDMA result.¹ Mild to moderate hemolysis does not impact IDEXX SDMA concentration, but IDEXX SDMA Test results may be depressed in markedly hemolyzed specimens. In addition, it is rare that SDMA cannot be measured in specimens with extreme hemolysis and lipemia. However, as with all laboratory testing, quality specimens free of lipemia and hemolysis are preferred to provide the most accurate results.

SDMA, like creatinine and GFR, has a biologic variability of 15%–20% from measurement to measurement in the same patient over a week or more. Therefore, changes need to be greater than this to indicate a true change and significant difference. For example, with 20% biologic variability, an initial SDMA result of 14 µg/dL could recheck anywhere from 11–17 µg/dL based on biologic variability alone, just like a creatinine of 1.5 mg/dL could vary from 1.2–1.8 mg/dL.^1,2

Because SDMA correlates well to GFR,^1,3–6 medication that affects GFR may result in changes to SDMA concentration.

SDMA is a surrogate marker for GFR.^1,3–6 Biological variation of SDMA may range from 15%–20%, so it is important to consider this when interpreting any changes in SDMA.² SDMA may also be affected by hydration status, so ideally, SDMA should be interpreted in a patient that is euvolemic and with a complete urinalysis to assess urine concentrating ability. SDMA may decrease in a dehydrated patient that is restored to euvolemia; however, it is important to also consider urine specific gravity when interpreting results.

SDMA is a surrogate marker of GFR^1,3–6 and should not be affected by lower urinary tract infection in an otherwise well animal. In a patient with decreased GFR and/or underlying kidney disease, including AKI, SDMA may be increased, reflecting underlying changes in kidney function.

This has not been studied specifically in animals, but it has been confirmed that there is no correlation in dogs and cats between SDMA and serum arginine concentrations.^1,7 In addition, in pregnant women with preeclampsia receiving prolonged supplementation with L-arginine, there was no impact on serum SDMA concentrations.⁸

SDMA correlates strongly with GFR.^1,3–6 Dogs and cats demonstrate measured alterations in GFR, depending on the diet fed, and SDMA will be affected accordingly. However, unlike BUN, it is not expected that SDMA will be impacted by protein content of the diet or gastrointestinal bleeding independent of GFR.

Yes, using SDMA as a biomarker for CKD allows earlier diagnosis of CKD in both dogs and cats.^3,4 Patients diagnosed with CKD and treated with a therapeutic renal diet experienced delayed progression of CKD as compared to patients fed a maintenance diet.^5,9,10

The IDEXX SDMA Test is a sensitive kidney function test that helps to identify kidney disease in dogs and cats. If acute kidney injury is identified, then the underlying cause should be treated appropriately. If CKD has been diagnosed and SDMA and creatinine remain increased but stable, the animal should be staged using the IRIS CKD guidelines. We recommend veterinarians utilize the current IRIS treatment guidelines to help determine appropriate treatment.¹¹

Dietary therapy is a key component for management of CKD in dogs and cats. Kidney therapeutic diets have controlled amounts of protein and are phosphorus-restricted, nonacidifying, and often supplemented with antioxidants and omega-3 fatty acids.

When deciding the appropriate time to begin feeding a kidney therapeutic diet to a patient with CKD, follow your clinical experience and utilize the current IRIS CKD treatment guidelines. According to the guidelines, it is appropriate to start a renal therapeutic diet when dogs and cats are in IRIS CKD Stage 1 if they have persistent renal proteinuria (UPC ratio greater than 0.4 in cats and 0.5 in dogs) or are in IRIS CKD Stage 2.¹¹

For nonproteinuric, IRIS CKD Stage 1 dogs and cats, there is emerging evidence that feeding a renal-supportive diet can be beneficial.¹¹

Starting a kidney therapeutic diet at the earliest appropriate time is ideal because transitioning to a new food should be more successful when the patient’s appetite is still good. Maintaining body weight and muscle is essential to successful management of CKD, and this is achieved primarily by adequate caloric intake.¹¹