CLINICAL PATHOLOGY
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ter measured against “individual normal” than population normal ranges. The sensitivity of creatinine for
diagnosing renal failure increases significantly if we
establish the patient’s own baseline intervals as that
enables us to trend creatinine and thereby detect persistent increase in creatinine.
Gold standard in evaluating kidney function
The absolute gold standard in evaluating kidney function in a patient is to perform a clearance test for the
calculation of Glomerular Filtration Rate (GFR).
Iohexol and inulin clearance are both looked upon as
gold standard tests and a reliable exogenous creatinine clearance test has also been commercially available for some years. The challenge of doing regular
clearance tests in veterinary practice is that is often requires special equipment, it takes time, as blood and
urine has to be collected several times within a given
time interval and it is a costly diagnostic procedure.
For these reasons, although available, it is performed
very rarely in veterinary practice outside of referral
hospitals and university hospitals.
The big desire for many years has therefore been to
find a single test that could give a valid estimate of the
GFR, earlier in the course of renal deterioration than
creatinine, without doing an actual clearance test.
SDMA is created by methylation in arginine in any
nucleated cell during protein production. SDMA is
released into the blood stream and excreted only
through the kidneys. This means that the level if SDMA
in the blood equals the kidney’s filtration rate.
Veterinary research on this parameter started about
a decade ago and IDEXX laboratories has worked intensely with different universities and the International
Renal Interest Society (IRIS) to look further into this.
Hills nutrition has played a very vital role as a great
deal of the validation studies has been done on their
pet colony.
The three key attributes of SDMA
•
•
•
It correlates with GFR, hence it is a biomarker for
kidney function
It is specific for kidney function
It is an earlier indicator of renal dysfunction.
Being specific for renal function means that SDMA is
not impacted by lean body mass, breed, age or sex.
Nor is it impacted by arginine levels in the body, liver
function and diet.
The independence of lean body mass is in particular interesting as when patients start going into renal
failure, often they lose weight which can falsely decrease the creatinine concentration, SDMA will not be
impacted by this.
SDMA and early diagnosis
SDMA is an abbreviation for Symmetrical Dimethyl Arginine. It is not a new test as such, as it has been used
to evaluate renal function in humans for many years.
It is new to veterinary diagnostics and has now been
validated for use in dogs and cats. A veterinary specific
analysis has been created and released this year, the
IDEXX SDMA™.
Being and earlier indicator of renal disease than creatinine is also a very promising feature. Studies have
shown that in average SDMA is significantly increased
when 40% of the kidney function is lost as opposed
to creatinine being increased when 75% is lost. SDMA
has also been seen to be elevated when as little as
25% of the kidney function is lost.
3 Key Attributes of SDMA
Earlier than
creatinine
Biomarker for
kidney function
April 2016 Vet360 for Madaleen Review.indd 35
SDMA
This enables us to detect these sub-clinical CKD patients much earlier. Studies
together with Hills showed that in average SDMA is increased 9 months earlier
than creatinine in dogs and 17 months
earlier than creatinine in cats. Seventeen
months is a long time in a feline li