What is SDMA?
SDMA or Symmetric
dimethylarginine is a biomarker and amino acid arginine that contains two
methyl groups in a symmetrical orientation which is excreted by kidneys. It gives
more accurate and reliable value of glomerular filtration rate (GFR) than
creatinine in dogs and cats. SDMA was first identified in human urine in the
year 1970. The first clinical study in veterinary patients was published in 2008
for SDMA levels associated with CKD (Chronic Kidney Disease) in cats.
SDMA is recommended for dogs or cats?
helps in the early detection of the kidney disease in dogs and cats. It can
diagnose kidney disease in dogs and cats months or years earlier than the standard
screening technologies (blood chemistry parameters, blood urea nitrogen,
creatinine and urine specific gravity). In research it has shown in one animal
4 years early detection of the kidney problem. SDMA has 91% specificity and 100%
sensitivity for kidney disease in dogs and cats. In fact about one out of ten senior dogs will have some form of
kidney disease over their lifetime while it is 1 out of 3 in senior feline
patients over age 15. At early stages kidney disease has no visible signs and
cats actually can hide disease even at advance stage so pets suffering from
kidney disease may appear normal.
serum SDMA levels
SDMA concentration increases in the case of decreased kidney function. It can be
due to acute kidney injury (AKI) or chornic kidney disease (CKD) in dogs and cats. It is
slightly higher in growing puppies than adult dogs.
Fig: SDMA level interpretation and use (adapted and modified from IDEXX SDMA)
v/s Creatinine – Reliability
It is more specific and less
affected by other body conditions with weight and muscle loss, advanced age and
disease state. It does not appear to be absorbed in the renal tubules of
influenced by many non-renal factors. Creatinine is not useful in diagnosing
kidney health until almost 75% or kidney function is lost but SDMA does it as early
as 25% both in chronic and acute kidney injury. In cases of untreated
hyperthyroidism increased GFR and loss of muscle mass is common which can hide
underlying CKD but SDMA is only slightly affected by hyperfiltration and not
affected by lean body mass. This makes it a more reliable tool for diagnosis of
CKD (chronic kidney disease).
is very uncommon when creatinine is increased and SDMA concentration is normal.
Haemolysis can result into decreased SDMA serum concentrations. Creatinine can
be increased in case of muscular dogs and postprandially though having normal
Creatinine is complementary
to SDMA for the evaluation of kidney health. A complete history, blood profile including CBC, serum electrolyte profile
with kidney function parameters, urine analysis (including urine protein
creatinine ratio and specific gravity), physical examination and radiodiagnosis/ultrasound is helpful in the complete evaluation of kidney health. CKD cannot be
reversed or cured but treatment and management aimed at reducing the
contributing factors and symptoms can slow its progression.
Benefits of SDMA and early
diagnosis of CKD
Early diagnosis of CKD helps
in the investigation of the cause of kidney disease and management. Conditions like
infections, obstruction, exposure to nephrotoxic drugs can be treated at early
stage and assessment of hydration status, blood pressure and thyroid status cab
Future insult to the kidneys
can be avoided by taking precautions if diagnosed early. Treatment can be initiated and can be
monitored easily with regular tests. Serum SDMA helps in the prediction of the
impact of the hyperthyroidism treatment on kidney function test in cats and
helps in identifying which cat will become azotemic after treatment.
or heparinized plasma can be used for the performing test.
in cats and dogs, it is stable for one week at room temperature. Stable over a
year at -20°C or -80°C and for two weeks at 4°C.
Reference ranges of serum SDMA
Cat / Kittens: 0-14 µg/dL
Puppies: 0-16 µg/dL
reference range in kittens and adult cats is almost similar. The adult range can be
used in kittens. Serum SDMA reference levels in puppies have been determined
slightly higher than the adult. It is mainly during the rapid growth phase (rapidly
growing puppies up to 14-16 µg/dL) and can be determined again as the growth
phase slows down. In cases of high SDMA levels, urine analysis and other
evidence of kidney disease can be checked in puppies. SDMA level normalizes as the puppy reaches adulthood. Toy breeds
attain adulthood earlier than giant breeds. The exact cause of high reference level
can’t be explained in puppies but physiological roles for protein arginine
methylation, protein translocation, DNA repair, mRNA splicing, transcriptional
control, signal transduction are postulated to be a reason of an increase in SDMA
levels. High SDMA concentrations always do not mean renal dysfunction or the
renal dysfunction was transient.
dogs and cats lean body mass do not appear to influence serum SDMA levels. It
has shown that in humans dietary arginine has no effect on serum SDMA
concentrations so it remains unaffected with diet.
SDMA to creatinine ratio greater than 10 in dogs and cats were associated mortality
within 1 year. So it may have good prognostic value. Dogs or cats having high
serum SDMA concentrations (>16 µg/dL) along with high urine specific gravity
i.e. > 1.040 more likely to have prerenal azotemia if dehydrated. Cats and
dogs having borderline increase in serum SDMA and creatinine concentration
should be tested again after two weeks of initial screening and every three
months to assess the renal function performance and stability. Other tests
should also be performed to ensure potential renal disease and associated
kits also available form bionote in the name of Vcheck SDMA for feline and
canine SDMA while IDEXX SDMA kits are the first choice worldwide.
Ernst, R. et
al. 2018. Comparative performance of IDEXX SDMA Test and the
DLD SDMA ELISA for the measurement of SDMA in canine and feline serum. PLoS
One. 2018 Oct 15;13(10):e0205030. doi: 10.1371/journal.pone.0205030.
J. A. et al. 2014. Comparison of serum concentrations of symmetric
dimethylarginine and creatinine as kidney function biomarkers in healthy
geriatric cats fed reduced protein foods enriched with fish oil, L-carnitine,
and medium-chain triglycerides. Vet J 2014;
Relford, R. et al. 2016. Symmetric Dimethylarginine:
Improving the Diagnosis and Staging of Chronic Kidney Disease in Small Animals.
Vet Clin North Am Small Anim Pract. 2016 Nov;46(6):941-60. doi:
10.1016/j.cvsm.2016.06.010. Epub 2016 Aug 5.
K. et al. 2005. Effects of prolonged oral supplementation with
L-arginine on blood pressure and nitric oxide synthesis in preeclampsia. E J Clin Invest 2005; 35:32-37.
M. et al. 2015. Prognostic value of symmetric dimethylarginine to creatinine
ratio in dogs and cats with chronic kidney disease. Proc ACVIM Forum, 2015. acvim.org, accessed 2015.
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