Why Is My Dog's Sed Rate Increased ?
Why Is My Cat's Sed Rate Increased ?
To see what normal blood and urine values are for your pet, go here
For an explanation of causes of most abnormal blood and urine tests go here
To see how tests are often grouped, go here
Ron Hines DVM PhD
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Your Pet's Blood Sedimentation Rate
aka Erythrocyte Sedimentation Rate, Sed Rate, ESR, Westergren ESR
See a slightly different explanation here.
This vintage test (since 1897) does little more than confirm to your veterinarian that your dog or cat really has a health issue. It measures how fast your pet’s red blood cells (RBCs) sink to the bottom of a glass tube in which a blood sample with added anticoagulants was placed.
That rate, measured over a period of one hour, increases when inflammation is present anywhere in the body. The test relies on changes in the electrical charges between RBCs that keep them in suspension versus clotting factors that cause RBCs to stick to one another (rouleaux formation, high fibrinogen) and sink to the bottom. Because anemia markedly increases your pet's sedimentation rate, laboratories have a mathematical formula to correct the ESR number (value) when anemia is present.
Tests like the ESR are called “high sensitivity-low specificity” tests. Like having a fever, they tell you there is a problem – but not what it is. More modern tests that detect inflammation like C-reactive protein (they monitor acute-phase response) have largely replaced the ESR.
The ESR test might also have value in deciding if your pet is responding well to treatment.
Reasons Why Your Pet’s Sed Rate Could Be Increased :
A common cause for an elevated ESR rate in dogs and cats is anemia.
The ESR rate also goes up significantly in sudden (acute) generalized infections – the kinds that affect the whole body, cause widespread inflammation, produce fever and make your dog or cat visibly ill.
Pets with severe long-standing arthritis, or cancer that is causing visible decline in their health can also increase their ESR rate.
Sed rates were once reported to be elevated in dogs with roundworm infection – but other health factors could have been the underlying cause.
Reasons Why Your Pet’s Sed Rate Might Be Decreased :
Blood samples that have been stored tend to give falsely lower ESR rates - particularly if that storage was at room temperature and not in the fridge.
It is said that hemolytic anemia – the kind of anemia due to toxins or antibodies that destroy a pet’s red blood cells while they are still in circulation – can decrease ESR rates. It is possible that low blood fibrinogen levels due to liver disease could slow your pet's ESR rate as well.