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Glycated Hemoglobin Heartworm Microfilarial Filter Testing 1349

Reference Interval Important Interspecies Differences allow the sample to reach room temperature
Negative in healthy patients; stressed cats may The renal tubular threshold for glucose is before processing.
VetBooks.ir reported in semi-quantitative values. Drug Effects Relative Cost: $ (reported as part of
≈180 mg/dL in dogs and ≈280 mg/dL in cats.
have transient glucosuria. Positive results are
urinalysis)
Causes of Abnormally High Levels
concentrations of ascorbic acid.
• With concurrent hyperglycemia: diabetes False-negative results can occur with high Pearls
mellitus, hyperadrenocorticism, stress (cats), • Owners of diabetic dogs should be discour-
pancreatitis, pheochromocytoma Lab Artifacts aged from altering insulin dose based on
• With concurrent euglycemia: renal tubular Contamination with oxidizing agents (e.g., home monitoring of glucosuria.
damage (e.g., nephrotoxicity), Fanconi bleach) can result in false-positive results. • Owners of diabetic cats who notice glucosuria
syndrome, primary renal glucosuria consistently absent via home monitoring
Specimen Collection and Handling should contact their veterinarian as disease
Next Diagnostic Steps to Consider Avoid collection of urine off exam table or may be in remission.
if Levels Are High floor to prevent potential contamination with
Measure plasma glucose and/or fructosamine oxidizing agents. If refrigerated for storage, AUTHOR: Shannon D. Dehghanpir, DVM, MS, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
to exclude diabetes mellitus.

Glycated Hemoglobin

Definition Causes of Abnormally High Levels Important Interspecies Differences
Hemoglobin (Hgb) with nonenzymatically Persistent hyperglycemia (diabetes mellitus) Not all human Hgb A 1c assays are validated
added glucose is referred to as glycated or glyco- for use in veterinary species.
sylated Hgb. Can be used to monitor therapy in Next Diagnostic Steps to Consider
diabetic patients; however, use of fructosamine if Levels Are High Lab Artifacts
for this purpose is far more common. Results Increased glycated Hgb indicates insulin therapy Varies with methodology used; contact your
usually reported as the % glycated Hgb out of and other glycemic management protocols may laboratory for more information.
total Hgb but may instead be reported as the need to be optimized. Serial glucose measure-
total concentration of glycated Hgb. ments (glucose curve) may be necessary to better Specimen Collection and Handling
tailor therapy. • Collect blood into an EDTA (purple top)
Synonyms tube. Refrigerate and ship sample with cold
Glycosylated Hgb. Hgb A 1c is a specific form. Causes of Abnormally Low Levels packs. Refrigerated blood is considered stable
Persistent hypoglycemia, recent hemorrhage or for a week before analysis. Storage at room
Physiology hemolysis resulting in a skewed proportion of temperature may decrease results.
The degree of increase in glycated Hgb con- young erythrocytes (and thus less glycated Hgb), • Recently, an A1c test kit has been marketed Laboratory Tests Laboratory Tests
centration in a patient is dependent on the anemia of any type will decrease total glycated for dogs and cats (A1Care, Baycom Diag-
magnitude and duration of hyperglycemia Hgb concentration. nostics). A drop of whole blood is applied
over the span of approximately 2 months. to a test card that is mailed out for analysis.
Altering the total Hgb concentration (anemia, Next Diagnostic Steps to Consider
erythrocytosis) will accordingly change the total if Levels Are Low Relative Cost: $$
glycated Hgb concentration. Decreased glycated Hgb in a diabetic patient
receiving insulin suggests that therapy has been AUTHOR: Angela Royal, MS, DVM, DACVP
Reference Interval causing periods of hypoglycemia. Treatment EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
Varies by laboratory. Example: 1.7%-4.9% protocol should be re-evaluated, and serial glucose
(dogs) measurements (glucose curve) may be warranted.

Heartworm Microfilarial Filter Testing

Definition Physiology Reference Interval
Diagnostic testing for the qualification of This test enhances the sensitivity of identifica- Reported as “No microfilariae observed” or
microfilariae such as Dirofilaria immitis tion of microfilariae in the blood via concen- “Microfilariae observed”
tration and lyses of erythrocytes via trapping
Synonyms the microfilariae (L1) on a polycarbonate Causes of Abnormally High Levels
Knott’s test, heartworm filter test filter. Microfilarial loads from Dirofilaria spp. or
Acanthocheilonema reconditum infection

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