Page 2689 - Cote clinical veterinary advisor dogs and cats 4th

1388 Triglycerides

tachyzoites, and fulminant systemic clinical with clindamycin) as a diagnostic test in patients Lab Artifacts
disease. with compatible clinical signs and a positive False-positive ELISA: lipemia and hemolysis
VetBooks.ir Reference Interval aqueous humor, whole blood, respiratory Specimen Collection and Handling
IgM or rising IgG titer.
PCR test on cerebrospinal fluid (CSF),
Serum (red top tube), 1 mL. CSF or aqueous
Reported as titer values with interpretation
Causes of Abnormally High Levels lavage fluid, or fresh tissue to demonstrate humor (lavender top tube), 0.5 mL. Stable
presence of Toxoplasma DNA. Definitive diag-
for 5 days at 2°C-8°C or longer frozen. Paired
ELISA or IFA: positive IgG with negative IgM nosis requires demonstration of tachyzoites or serum samples should be submitted to the same
titer most consistent with chronic exposure to T. cysts cytologically or histopathologically (with laboratory for testing at the same time.
gondii (≥ 2 weeks post-infection). Recent exposure immunohistochemistry) and/or PCR, or rarely
or active infection typically results in positive via animal or cell culture inoculation. Relative Cost: $$ (ELISA, PCR, IFA)
IgM with negative IgG titer (1-2 weeks post-
infection) or both positive IgM and IgG titer. Causes of Abnormally Low Levels Pearls
Up to 20% of cats may not develop positive Negative IgG and IgM titers indicate absence • Value of a single IgG measurement is very
IgM titer during active infection. Conversely, of exposure, peracute infection, or insufficient limited because approximately 30% of
some cats, especially those concurrently infected immune response to infection. healthy cats and dogs have a positive titer.
with feline immunodeficiency virus, may have • No single serologic assay can definitively
IgM titers that persist for months to years after Next Diagnostic Steps to Consider confirm a diagnosis. IFA has more false-
infection. Since infected animals harbor tissue if Levels are Low positives than ELISA; at low dilutions the
cysts for life, a long-term measurable IgG titer is If clinical signs are suggestive of acute toxoplas- specificity of ELISA may be lower than IFA.
expected. Positive titer does not indicate oocyst mosis, re-evaluate IgM and IgG titers in 3-6 • IgG-seropositive, IgM-seronegative cats
shedding. weeks or consider alternative testing (p. 984). are unlikely to be shedding oocytes. IgM-
seropositive cats might or might not be
Next Diagnostic Steps to Consider Drug Effects shedding oocysts (period of shedding occurs
if Levels are High Clindamycin may decrease IgM titer, but will briefly soon after infection).
If IgG titer is positive, evaluate IgM titer or not affect IgG titer. High doses of corticosteroids
paired IgG titers (2-3 weeks apart). Greater than administered to cats with latent infection AUTHOR: Patty J. Ewing, DVM, MS, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
fourfold increase in paired IgG titers indicates may decrease IgG titers and increase IgM
recent exposure. Some infectious disease special- titers.
ists recommend response to treatment (e.g.,

Triglycerides

Definition in Brittany spaniels, mixed-breed dogs Important Interspecies Differences
Main storage form of long-chain fatty acids and cats); familial hyperchylomicronemia Hyperlipidemia may occur in cholestatic liver
in cats disease. Cats with hepatic lipidosis do not have
Synonym • Secondary hyperlipidemia: postprandial, hyperlipidemia.
Triacylglycerol hypothyroidism (dogs), diabetes mellitus,
pancreatitis, hepatic disease, nephrotic Drug Effects
Physiology syndrome, hyperadrenocorticism, high-fat • Increased: doxorubicin, exogenous
Three fatty acid molecules are bound (esterified) diet, acromegaly (cats) corticosteroids, megestrol acetate
to a glycerol backbone to form a triglyceride • Decreased: lipid-lowering diets, supplementa-
molecule, the main lipid in adipose tissue/ Next Diagnostic Steps to Consider tion with fish oils, nicotinic acid and fibric
body fat. Primary sites of triglyceride synthesis if Levels are High acid derivatives such as gemfibrozil
are liver, small intestine, adipose tissue, and • Measure fasting levels (minimum 12-hour
mammary gland, but synthesis occurs in most fast) to rule out postprandial hyperlipidemia. Lab Artifacts
cells. Triglycerides are transported in the blood If persistent, assess for causes of secondary Hemolysis, lipemia, increased fluid viscosity,
bound to apoproteins, forming complexes called hyperlipidemia. If secondary hyperlipid- and glycerol artificially elevate triglyceride
lipoproteins. Circulating triglyceride levels emia is ruled out, primary hyperlipidemia levels.
reflect a balance of absorption and synthesis is diagnosis of exclusion. See pp. 496
by the small intestine, synthesis and secretion and 1236. Specimen Collection and Handling
by hepatocytes, and uptake by adipose tissue. Ensure sample collected after 12-hour fast.
These processes are affected by dietary fat intake Causes of Abnormally Low Levels Serum (red top tube), heparinized plasma
and hormones (insulin, glucagon). Malabsorption/maldigestion; hepatic synthetic (green top tube), or EDTA plasma (lavender
failure (chronic hepatopathies) top tube). Stable at 2°C-8°C for 1 week, 3
Reference Interval months frozen at −20°C
Serum levels, dogs: 20-150 mg/dL; cats: 20-90 mg/ Next Diagnostic Steps to Consider
dL. Unit conversion: 1 mg/dL = 0.0113 mmol/L. if Levels are Low Relative Cost: $$
Serum trypsin-like immunoreactivity (TLI),
Causes of Abnormally High Levels cobalamin (vitamin B 12) and folate levels; Pearls
• Primary hyperlipidemia: idiopathic hyper- assess for panhypoproteinemia; serum bile • Triglyceride levels may be measured in sus-
lipidemia (schnauzer, beagles, and rarely acids (pre- and postprandial) pected chylous effusions. Triglyceride levels

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