Page 2604 - Cote clinical veterinary advisor dogs and cats 4th

1320 Buffy Coat Calcium, Serum

Buffy Coat
VetBooks.ir Definition Next Diagnostic Steps to Consider

are less dense than normal erythrocytes and
The thin white layer of packed leukocytes and if Levels Are High • In dogs with babesiosis, infected erythrocytes
platelets found atop the packed erythrocytes CBC with blood smear examination, smear can occur in higher numbers on buffy coat
following high-speed centrifugation of antico- with evaluation of buffy coat itself smears.
agulated blood • Low numbers of circulating mast cells
Specimen Collection and Handling detected on buffy coat smears occur as an
Physiology EDTA whole blood (lavender top tube), or incidental finding in dogs (and rarely in
Leukocytes and platelets are less dense than immediately filled and spun hematocrit tube cats) with various inflammatory diseases.
erythrocytes, so they deposit above the packed Therefore, buffy coat detection of mast
erythrocytes following centrifugation. Relative Cost: $$ cells is seldom used to screen for mast cell
neoplasms.
Reference Interval Pearls
Typically not measured. The height of this layer • Smears of buffy coat cells can be used for AUTHOR: Stephen D. Gaunt, DVM, PhD, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
in a spun blood specimen can be a crude index concentrating abnormal leukocytes that occur
of the total leukocyte count. in very low numbers. Examples: detection of
mastocytemia as a staging tool in dogs with
Causes of Abnormally High Levels mast cell neoplasm, detection of infectious
Any condition causing leukocytosis or throm- agents in neutrophils or monocytes (e.g.,
bocytosis can increase the thickness of the buffy Histoplasma in dogs and cats, Hepatozoon
coat layer. americanum or Ehrlichia morulae in dogs)

Calcium, Serum

Definition kidney injury (including grape/raisin intoxica- Drug Effects
Essential mineral with important regulatory tion), idiopathic (cats), hypoadrenocorticism, • Increase: thiazide diuretics, supplements or
functions (cell signaling). Serum total calcium hyperproteinemia, excess supplementation, rodenticides containing vitamin D, excess
2+
(tCa ) includes protein-bound (35%-40%), physiologic (young dogs). See p. 1232. oral phosphate binders, antipsoriasis creams
2+
anion-complexed (10%), and ionized (iCa ) • Decrease: furosemide, glucocorticoids, phos-
2+
(50%-55%) fractions. Next Diagnostic Steps to Consider phate enemas, calcitonin, mithramycin, Ca -
if Levels are High binding anticoagulants (in blood transfusion
Synonyms Interpret with serum [phosphorus], physical products), bicarbonate administration
Ca, Ca 2+ exam (including rectal palpation for anal sac
neoplasm and careful lymph node palpation), Lab Artifacts
Physiology and other laboratory data. Measure serum • Decreased: inappropriate anticoagulant
2+
2+
Serum levels are regulated by parathyroid [iCa ]. If ionized hypercalcemia, consider (EDTA, citrate, oxalate bind Ca in vitro)
2+
hormone (PTH) and calcitriol (vitamin D measuring PTH, PTHrP. • Decreased [iCa ]; aerobic sample handling,
metabolite), affecting intestine, kidney, and over heparinization
2+
bone. Dietary absorption depends on calcitriol. Causes of Abnormally Low Levels • Increased [iCa ]; prolonged exposure to
2+
2+
Glomeruli filter non–protein-bound Ca ; 98% Hypoalbuminemia (iCa normal despite low erythrocytes, use of serum separator tubes
2+
2+
is reabsorbed by tubules. Low [iCa ] stimulates tCa ), puerperal tetany, hypoparathyroidism, (SST). The gel plugs of SST are reported to
2+
PTH production, mobilizing Ca from bone, 2° hyperparathyroidism, hyperadrenocorticism, leak calcium into the serum sample.
increasing renal tubular resorption, stimulat- ethylene glycol intoxication, pancreatitis, • Effects of bilirubin, lipemia, and hemolysis
ing calcitriol synthesis. In hypercalcemia of malabsorption syndromes, hypomagnesemia, are instrument/assay dependent
malignancy, PTH-related peptide (PTHrP) hypovitaminosis D (including renal disease),
2+
mimics actions of PTH. iCa is the biologically acute tumor lysis syndrome, severe tissue Specimen Collection and Handling
active form. trauma, sepsis. See p. 1239. • Serum (red top tube) preferred; heparinized
plasma (green top tube) may be used.
Reference Interval Next Diagnostic Steps to Consider • iCa : anaerobic handling necessary. Harvest
2+
2+
• Total Ca : 8.5-11 mg/dL; 4.2-5.5 mEq/L if Levels are Low serum or plasma within 1 hour. Serum is
2+
(2.1-2.75 mmol/L) Measure serum [iCa ], albumin. Interpret preferred. Do not use serum separator tubes.
2+
• Ionized Ca : 4.5-6 mg/dL; 2.2-3 mEq/L with physical exam, relevant history, and other Do not freeze. Heparin concentration should
2+
(1.1-1.5 mmol/L) laboratory data. Measurement of PTH, Mg not exceed 4% of blood volume in tube.
may be of use in select cases. Heparinized whole blood used by some
Causes of Abnormally High Levels portable point-of-care analyzers
Hypercalcemia of malignancy, primary Important Interspecies Differences
hyperparathyroidism, osteolysis, granulomatous Cats may have idiopathic increase in Relative Cost: $ (single test); $$ (as part
diseases, hypervitaminosis D, kidney disease/ iCa 2+ of panel)
www.ExpertConsult.com
www .ExpertConsult.com