SDMA Testing's Role in Pets with Infectious Disease
SDMA (Symmetric dimethylarginine) is a sensitive, reliable indicator in change and decrease of glomerular filtration (GFR). As such, it can help identify a decline in kidney function in pets with infectious disease—particularly vector-borne diseases that often affect the kidneys—or even be a clinical flag to investigate for exposure to these diseases in endemic areas.1,3.5,19-20
Here, we'll explore the link between SDMA and infectious diseases and explain why it's important to include SDMA to evaluate kidney function as an indication of total systemic health, especially in dogs with exposure to certain vector-borne diseases or cats with feline leukemia virus (FeLV) or feline immunodeficiency virus (FIV).
What SDMA Tells Us About Kidney Function
As GFR declines, SDMA increases with an average of 40% loss and as little as 25% loss of kidney function. This is in comparison to creatinine which doesn't increase until approximately 75% of kidney function is lost1,2,5. According to the International Renal Interest Society, kidney disease is diverse and occurs on a continuum, with chronic kidney disease and acute kidney injuries often combining to lead to worsening function. Including SDMA evaluation can allow for early and consistent identification of changes in kidney health.
Infectious Disease and the Kidneys
Infectious and vector-borne diseases are a global medical issue, and while common diseases vary by geographic location, as veterinarians our role always involves understanding systemic health to the best of our ability. The kidneys are central to systemic health and are often concurrently affected by infectious diseases, whether as a rare but serious complication of Lyme disease, Bartonella endocarditis, or renal lymphoma due to FeLV, or from acute kidney injury (AKI) associated with vasculitis as can be seem with babesiosis or anaplasmosis.
Understanding kidney function is also important for medication choices and long-term infectious disease monitoring. Testing SDMA, in conjunction with novel biomarker Cystatin B, can provide critical information on kidney health—and potential kidney injury—in pets that require medication to treat infectious diseases. This information can help guide the dosing of certain antibiotics or other supportive medications with renal excretion. A persistent elevation in SDMA may even be a clinical flag to investigate for protein-losing nephropathy which can be associated with vector-borne diseases in endemic areas.
SDMA Testing for Dogs with Vector-Borne Disease
Dogs with exposure to vector-borne disease should be screened with a full chemistry panel to evaluate for signs of systemic manifestations of disease, and including SDMA in that panel can strengthen the evaluation of kidney health. In dogs, two recent studies have shown a link between exposure to particular vector-borne diseases and long-term risk of chronic kidney disease (CKD). Unsurprisingly, there was a link found between Lyme exposure and CKD: Dogs with a positive Lyme disease C6 antibody test result had a 43% increased risk of developing CKD.19 Maybe more surprisingly, in a study done on dogs from an area of the country with a high risk for Ehrlichia canis exposure via Rhipicephalus sanguineus ticks, there was an even stronger association with Ehrlichia spp. exposure and CKD.20 Dogs with a positive Ehrlichia spp. antibody test result had more than twice the risk of developing CKD compared to matched dogs without Ehrlichia exposure. Although neither study allows inference of a causal relationship, they both indicate a statistically significant association between tick-borne pathogen exposure and CKD. Because of this, and since SDMA is a sensitive and specific biomarker of kidney function, including it in chemistry profiles can help identify early changes to kidney function that may be a complication of previous vector-borne disease exposure or active disease.
SDMA Testing for Cats with FeLV or FIV
Retrovirus (FeLV or FIV) infection has recently been shown in association with proteinuria and immune-complex glomerulonephritis (ICGN) in cats. While rare, ICGN is treated differently from CKD in cats, so knowing the retrovirus status and having as much information as possible about infected cats' renal health is critical to appropriate management. Because there are no effective treatments widely available for feline retroviral infection, treatment relies on effective preventive health care strategies, and prompt identification and treatment of illness—all of which requires a complete picture of organ function.
SDMA adds to the robust evaluation of kidney function in pets with exposure to infectious disease, allowing evaluation of existing comorbidities that could change treatment recommendations as well as current disease manifestations. Understanding renal function is essential for appropriate treatment selection, comprehensive long-term monitoring, and effective client communication. Including SDMA testing for pets with retroviral infection or vector-borne disease exposure, especially dogs with positive tests for Ehrlichia spp. or Lyme disease, should be considered part of a routine evaluation of systemic health.
References: https://www.thevetiverse.com/en/latest/sdma-references/
