Page 2677 - Cote clinical veterinary advisor dogs and cats 4th

Reticulocytes Rheumatoid Factor (RF) 1379

Specimen Collection and Handling not use whole blood, hemolyzed or lipemic cats. It is also useful for ruling out pseudocyesis/
Plasma or serum, 1 mL. Collect blood in EDTA samples. pseudopregnancy (nondetectable in pseudopreg-
VetBooks.ir or heparin (green top tube) or serum (red top Relative Cost: $$$ AUTHOR & EDITOR: Lois Roth-Johnson, DVM, PhD,
nant patients).
(lavender top tube), citrate (blue top tube),
tube). Spin down, collect plasma or serum,
DACVP
Pearls
and transfer to a clean tube without additives
0
0
and label plasma or serum. Store at 2 C-8 C Relaxin is the only protein found to be associ-
up to 48 hours; freeze for longer storage. Do ated specifically with pregnancy in dogs and

Reticulocytes

Definition Causes of Abnormally High Levels intraerythrocytic inclusions (e.g., basophilic
Erythroid precursors that have expelled their Regenerative anemias from blood loss or hemolysis stippling, siderotic or Pappenheimer bodies,
nuclei and have larger volume, more ribosomes (p. 1307) are the most common cause of reticu- Heinz bodies, leukemic cell fragments,
and RNA, and less hemoglobin than mature locytosis. Increased reticulocytes in the absence of Babesia spp inclusions) or large or clumped
erythrocytes (that is, immature erythrocytes). anemia could suggest compensatory response for platelets could falsely increase the reticulocyte
Name derived from reticulum that forms after low-grade hypoxia or hemolysis. However, reticu- concentration.
RNA is precipitated by supravital dyes (e.g., locytosis without anemia is increasingly linked to
new methylene blue). See p. 1327. drug therapy (e.g., glucocorticoids, NSAIDs) or Specimen Collection and Handling
dietary supplements (e.g., glucosamine, omega-3 EDTA whole blood (lavender top tube) for flow
Synonym fatty acids) that stimulate erythropoiesis. cytometric counting by analyzers (preferred) or
Polychromatophilic erythrocyte manual counting of supravital stained smears
Next Diagnostic Steps to Consider
Physiology if Levels Are High Relative Cost: $ (reflex reticulocyte counts
With increased erythropoietin and proliferation Determine specific cause of blood loss or hemo- in anemic animals part of some CBC profiles)
of erythroid precursors, increased numbers of lysis if the patient is anemic. Reticulocytosis
reticulocytes are released into blood. In cats, without anemia may reflect an incidental Pearls
two forms of maturating reticulocytes are finding (see above). • An increase in absolute concentration (rather
identified with supravital stains (e.g., new than percentage) of reticulocytes is the gold
methylene blue). Aggregate reticulocytes have Causes of Abnormally Low Levels standard for determining whether anemia is
increased RNA that forms a prominent reticu- Nonregenerative anemias (p. 1306) or recent regenerative or nonregenerative.
lum; these correspond to polychromatophilic onset of anemia (≈3-7 days is required for • Because the absolute number of reticulocytes
erythrocytes on Romanowsky-stained smears regenerative response) is preferred over reticulocyte percentage,
and reticulocytes detected by hematology correction equations for anemic animals are Laboratory Tests
analyzers. Punctate reticulocytes have less Next Diagnostic Steps to Consider no longer in widespread use. Reticulocyte
RNA that forms pinpoint inclusions and are if Levels Are Low count may not be included in routine CBC;
not apparent on Romanowsky-stained smears See p. 63. Bone marrow aspirate or core biopsy request count when CBC performed on
or included in automated reticulocyte counts. often useful for nonregenerative anemia. anemic patients.
This distinction has limited clinical significance • Following acute blood loss or hemolysis,
since manual reticulocyte counts are performed Important Interspecies Differences increased numbers of reticulocytes are not
infrequently in cats. Dogs mount a higher reticulocyte response than expected to occur in peripheral blood until
cats during regenerative anemias. Cats demonstrate at least 3 days afterward.
Reference Interval different types of reticulocytes (see Physiology).
3
• Dogs: (nonanemic): < 80-95 × 10 AUTHOR: Stephen D. Gaunt, DVM, PhD, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
9
reticulocytes/mcL (or × 10 /L) Lab Artifacts
3
• Cats: (nonanemic): < 60 × 10 reticulocytes/ Autoagglutination may decrease the number
9
mcL (or × 10 /L) of detectable reticulocytes. Presence of

Rheumatoid Factor (RF)

Definition synovial fluid, and synovial tissues. Ongoing interpretation is specific for each reference
Autoantibodies to the Fc portion of autologous inflammation results in destruction of articular laboratory.
immunoglobulin (Ig)G cartilage.
Causes of Abnormally High Levels
Physiology Reference Interval • Rheumatoid arthritis. False-positive results
Immunoglobulins (predominantly IgM) form Reported as negative or positive; posi- are common and occur in animals with
complexes with RF in peripheral circulation, tive results are associated with titers, and (non-autoimmune) polyarthritis, heartworm

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