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Heinz Bodies Hematocrit 1351

Heinz Bodies
VetBooks.ir Definition Causes of Abnormally High Levels Drug Effects

Single or multiple precipitated denatured Drugs (see Drug Effects) and chemicals in food Acetaminophen, benzocaine-containing products,
hemoglobin particles on the erythrocyte mem- (onions, garlic, chives) or other substances (zinc, DL-methionine, methylene blue, phenacetin,
brane, often associated with oxidative damage. propylene glycol, skunk musk); deficiency of phenazopyridine, phenothiazine, and vitamin
See p. 1327. enzymes that protect against oxidants K 3 cause HB formation and hemolytic anemia.
Synonyms Next Diagnostic Steps to Consider Specimen Collection and Handling
Erythrocyte refractile body or ER body, HB, if Levels Are High EDTA whole blood (lavender top tube) for
Schmauch body • Review patient history (diet, drug or toxin CBC, Wright- and new methylene blue–stained
exposure, ingestion of metallic [zinc] foreign blood smears
Physiology objects, exposure to skunk musk).
Oxidants may cause irreversible denaturation • CBC, urinalysis, biochemistry profile: Relative Cost: $$ (reported as part of CBC)
of hemoglobin molecule, causing Heinz body anemia, hemolysis.
(HB) formation. HBs have affinity for, and Pearls
form a complex with, membrane protein band Important Interspecies Differences • Free HBs may falsely increase instrument
3 on both the internal and external erythrocyte • Normal in feline erythrocytes because of platelet counts and hemoglobin measurement.
membrane. HBs also make erythrocytes rigid innately unstable hemoglobin structure, • HBs may occur concurrently with eccentro-
and less deformable (via cross-linking of predisposition to form methemoglobin (low cytes (also a result of oxidative injury) and
spectrin and hemoglobin), making affected methemoglobin reductase activity), and inef- spherocytes (due to splenic removal of HBs
erythrocytes prone to intravascular and/or ficient removal by spleen. Normally occurring from red cell membranes).
extravascular hemolysis (erythophagocytosis by HBs are not associated with regenerative
splenic macrophages). anemia or hemolysis. Increased HB forma- AUTHOR: Fidelia R. Fernandez, DVM, MS, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
tion may occur without substantial anemia
Reference Interval in diabetes mellitus, hyperthyroidism, and
Low proportion seen in erythrocytes of normal lymphoma.
cats; uncommon in normal dogs • In other species, increased numbers of HBs
may be seen post-splenectomy.

Laboratory Tests
Hematocrit

Definition • Although PCV measures changes in Next Diagnostic Steps to Consider
The percentage of blood composed of erythrocyte volume as they occur in vivo, if Levels Are Low
erythrocytes. Electronic cell counters calcu- dilution of erythrocytes with normal saline Blood smear evaluation for type of anemia and
late hematocrit using this formula: (MCV and standing in hematology instruments may evidence of regeneration (e.g., polychromasia),
× RBC)/10 = HCT, where HCT is hema- cause erythrocytes to return to their normal absolute reticulocyte count, then further testing
tocrit, MCV is mean corpuscular volume volume. as indicated
(in femtoliters [fL]), and RBC is erythrocyte
6
count (×10 /fL). Provided Hb (hemoglobin) Reference Interval Important Interspecies Differences
reading is accurate (i.e., no interference Dogs: 36%-60%; cats: 29%-48% Greyhounds, whippets, salukis, Afghan hounds,
from hemolysis, lipemia, Heinz bodies, etc.), and dachshunds have slightly higher normal
HCT = Hb × 3. Causes of Abnormally High Levels values (up to 65% is considered normal, with
Erythrocytosis due to breed (sighthounds), some individuals exceeding even this level).
Physiology dehydration, splenic contraction (“relative
HCT values are slightly less than packed cell polycythemia”), hypoxemia, independent eryth- Drug Effects
volume (PCV, from centrifugation) because ropoietin production (e.g., renal neoplasia), or Erythropoietin injections increase HCT;
there is no trapped plasma in an HCT calcula- polycythemia vera (myeloproliferative disease of drugs toxic to bone marrow (hydroxyurea,
tion, as can occur with spun PCVs. Sources erythrocytes or primary absolute erythrocytosis) methimazole, many others) and drugs that
of variation: cause hemolysis (e.g., zinc, methylene blue,
• Due to the variable MCV of domestic Next Diagnostic Steps to Consider benzocaine) can decrease HCT.
animals, values for HCT may be erroneous if Levels Are High
if the instrument is not calibrated for specific Assess hydration status, review clinical history, Lab Artifacts
species. assess oxygenation, and evaluate for causes of • Hemolysis, lipemia, and specimen clotting
• Abnormal plasma osmolality and electrolyte erythrocytosis/polycythemia. prevent accurate reading.
balance may also result in a difference • Insufficient filling of EDTA (lavender top)
between HCT and PCV that is generally Causes of Abnormally Low Levels tube dilutes specimen, decreasing HCT; tubes
not clinically significant. Anemia, overhydration should be filled to capacity for accurate results.

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