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Anemia, Regenerative Anion Gap 1307

disease. Advanced diagnostic testing may Relative Cost: $ (reticulocyte count); $$ response. Therefore, in nonregenerative
include bone marrow evaluation, serologic tests (CBC; reticulocyte count included in some anemia of recent onset, serial CBC, blood
VetBooks.ir sis), thyroid function tests, serum ferritin or Pearls • Slow blood loss via the gastrointestinal
CBC panels)
smear evaluation, and reticulocyte counts
or PCR for infectious disease (e.g., ehrlichio-
are recommended.
folate.
Specimen Collection and Handling • Anemia due to early or acute hemolysis and tract (e.g., hookworms, gastric or intestinal
blood loss initially appears nonregenerative
ulceration) may also be associated with a non-
EDTA anticoagulated blood (lavender top tube) before the bone marrow has had time to regenerative anemia due to iron deficiency.
for CBC and absolute reticulocyte count; freshly respond. It takes ≈2-3 days after acute
made direct blood smear for morphologic hemolysis or blood loss for reticulocytosis AUTHOR: Fidelia R. Fernandez, DVM, MS, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
evaluation to be evident, and 7 days for an optimum

Anemia, Regenerative

Definition Causes of Abnormally High Levels Relative Cost: $ (reticulocyte count); $$
Anemia characterized by reticulocytosis; may Blood loss and/or hemolysis (CBC; reticulocyte count included in some
be accompanied by basophilic stippling, CBC panels)
Howell-Jolly bodies, and nucleated red blood Next Diagnostic Steps to Consider
cells (normoblastemia) if Levels Are High Pearls
Physical examination for evidence of blood • An absolute reticulocyte count is the most
Synonym loss (e.g., melena, ectoparasites); blood smear reliable means of assessing red cell regen-
Responsive anemia evaluation of red cell morphology for evidence eration. In the absence of a reticulocyte
of size, color, and shape changes, spherocy- count, a blood smear should be evaluated
Physiology tosis, agglutination, and parasitic inclusions. for polychromasia, but polychromasia does
Hypoxemia induced by decreased red cell Serologic or PCR tests for infectious disease not necessarily reflect the adequacy of
mass stimulates erythropoietin production in (e.g., hemotropic mycoplasmas, babesiosis). regenerative response.
the kidney and, subsequently, erythropoiesis. Coombs’ test. • Reticulocytosis in the absence of anemia has
See pp. 57, 59, and 60. been reported in association with the use of
Reference Interval NSAIDs and immunosuppressive drugs.
Packed cell volume (PCV) (dogs: 40%-55%; Lab Artifacts • Polychromasia and a high red cell distribu-
cats: 30%-40%); absolute reticulocyte counts Presence of Mycoplasma haemofelis inclusions tion width (RDW) more accurately identify
(percent reticulocyte × red blood cell count/ may falsely increase flow cytometric reticulocyte regenerative anemias in dogs than do red cell
mcL) of > 50,000/mcL (cats) and > 60,000/ counts. indices such as MCV.
mcL (dogs) indicate regeneration. Reticulocyte
percentage estimates are corrected for degree of Specimen Collection and Handling AUTHOR: Fidelia R. Fernandez, DVM, MS, DACVP Laboratory Tests
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
anemia; > 1% corrected indicates regenerative EDTA anticoagulated blood (lavender top
anemia. (Corrected reticulocyte % = [patient’s tube) for CBC and reticulocyte count; fresh
PCV/normal animal’s PCV] × uncorrected direct blood smear for morphologic evaluation
reticulocyte %; dog normal PCV ≈45% dogs) of red cells

Anion Gap

Definition anions (Cl , HCO 3 ) by about 5-15 mEq/L Next Diagnostic Steps to Consider
−
−
+
+
Calculated value using the formula [(Na + K ) (equivalent to the value of a “normal” anion if Levels Are High
−
−
− (Cl + HCO 3 )]. Represents the negatively gap). In health, the unmeasured anions are Review history for ethylene glycol exposure.
charged atoms and molecules in the bloodstream mostly charges on proteins. Organic acid (e.g., Evaluate serum biochemistry profile for azote-
other than those in the formula. lactic acid) accumulation increases the anion mia, hyperglycemia. Collect urine for specific
gap in disease states. gravity, ketone measurement, examination for
Physiology calcium oxalate monohydrate crystals. Perform
The total of positive and negative charges in Reference Interval blood gas analysis. Consider measuring lactate.
blood must be equal. Routine serum biochem- Dogs and cats: approximately 5-15 mEq/L
istry profile measures only some cations and (1 mEq/L = 1 mmol/L) Drug Effects
anions. “Unmeasured anions” (e.g., lactate, Potassium bromide may falsely increase
charged proteins) and “unmeasured cations” Causes of Abnormally High Levels serum chloride measurement, decreasing the
(e.g., magnesium, calcium) exist. Unmeasured Conditions usually causing metabolic acidosis, anion gap and often producing a negative
refers to anything other than the four ions most commonly lactic acidosis, uremia, keto- number.
included in the anion-gap formula. Measured acidosis, ethylene glycol toxicosis
+
+
cations (Na , K ) normally exceed measured
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