Hyperlipidemia in dogs and cats - Veterinary Medicine
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Hyperlipidemia in dogs and cats
Increased triglyceride or cholesterol concentrations will often normalize if they are caused by a secondary disease that is successfully treated. If the hyperlipidemia is primary, dietary modification and pharmacologic intervention may be required.


VETERINARY MEDICINE


Gross appearance of plasma or serum

Gross observation of the serum or plasma may assist in the diagnosis.1,2 The presence of fasting lipemia confirms hypertriglyceridemia. Lipemia becomes grossly detectable at triglyceride concentrations greater than 300 to 400 mg/dl (normal triglyceride concentration = 50 to 150 mg/dl in dogs and 50 to 100 mg/dl in cats) and is a result of the high concentration of large lipoproteins (chylomicrons and VLDLs).1 Elevated concentrations of cholesterol, without increases in chylomicrons or VLDLs, result in increases of LDLs and HDLs and do not affect the gross appearance of the serum or plasma.1

Chylomicron test


ESSENTIAL ELEMENT
A patient that presents with fasting lipemia can have elevations of chylomicrons, VLDLs, or both. To further evaluate such patients, a chylomicron test can be performed on lactescent serum by allowing the serum or plasma sample to sit undisturbed in a refrigerator for 12 to 14 hours.2 Chylomicrons are less dense than VLDLs and will float to the top of a chilled sample.2 The VLDLs are denser and tend to stay suspended within the serum or plasma. The formation of a creamy layer indicates the presence of chylomicrons. The absence of a creamy layer in a lipemic sample confirms increased VLDLs when the infranatant is cloudy. Formation of a creamy top-layer and cloudy plasma is indicative of excessive chylomicrons and VLDLs.2

The presence of chylomicrons alone can result from either familial or acquired diseases that result in reduced or absent lipoprotein lipase activity.2 However, the presence of VLDLs suggests that the hyperlipidemia is secondary to decreased or absent lipoprotein lipase activity or increased VLDL production.2 Both chylomicrons and VLDLs may be present in poorly regulated diabetic dogs.2

Triglyceride and cholesterol concentrations

Gross lipemia may not be evident in some patients with clinical signs compatible with hyperlipidemia. In these patients, determining fasting serum or plasma triglyceride and cholesterol concentrations is recommended. Total cholesterol is included on many serum chemistry profiles. A triglyceride concentration must be requested as an additional test. When assessing a patient for hyperlipidemia, submit refrigerated or frozen serum rather than plasma or whole blood.2


Table 4: Effect of Lipemia on Serum Chemistry Parameters in Dogs and Cats*
Lipemia can alter serum biochemical analysis. Chylomicronemia can interfere with other analytes determined by colorimetric methods (Table 4).2,3 Hyperlipidemia can also lead to in vitro hemolysis resulting from altered erythrocyte membrane fragility.2,12 Because of this interference, some laboratories clear lipemic samples by removing chylomicrons. If the laboratories do not report this, false negative results are possible. Therefore, submit paired lipemic samples to the laboratory—one for determining the triglyceride concentration and one to be cleared of chylomicrons and used to perform routine biochemical testing.


Table 5: Classification of Hyperlipidemia in Dogs and Cats*
Reference ranges for serum lipids vary widely depending on the specific laboratory methodology.1 So use species-specific reference ranges provided by the laboratory whenever possible. The guidelines used in our laboratory to assess the severity of hyperlipidemia in dogs and cats are presented in Table 5.


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Source: VETERINARY MEDICINE,
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