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Lead, Blood Level Left Shift 1357

Pearls conjunction with clinical signs and other AUTHOR: Ruanna E. Gossett, DVM, PhD, DACVP
Total serum LDH does not identify site-specific serum chemistry values are often sufficient EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
VetBooks.ir Inspection for hemolysis and evaluation in LDH.
for identifying the source of increased serum
isoenzymes, which requires electrophoresis.

Lead, Blood Level

Definition Reference Interval samples or those older than 24 hours can result
Whole blood lead levels are the diagnostic test Typical toxic range in whole blood in falsely decreased blood lead level (LeadCare
of choice to confirm or eliminate the diagnosis • 0.6 ppm or greater is diagnostic of toxicity. II analyzer).
of lead intoxication. • 0.35 ppm or greater with signs and confirma-
tory tests (D-aminolevulinic acid [ALA] or Relative Cost: $$$ (blood or tissue)
Physiology fecal lead) is also diagnostic.
Lead is generally poorly absorbed from the GI • > 20 mcg/mL (point-of-care analyzer, Pearls
tract but once absorbed, it is retained in soft LeadCare II) • Kidney, liver, GI tissue or feed may be
tissues and bone for months to years. Lead submitted. Kidney considered preferable
has deleterious effects on several physiologic Causes of Abnormally High Levels (≥ 10 ppm is diagnostic). Formalin-fixed
processes, including enzymes, erythrocyte Exposure to lead samples are acceptable.
and mitochondrial metabolism, and antioxi- • In animals, chronic exposure is more
dants. Blood lead is found primarily within Next Diagnostic Steps to Consider common than acute exposure.
erythrocytes; levels decline over time, but half- if Levels Are High • Blood levels and clinical signs do not always
life is variable. Elimination in dogs is primarily Consider radiographs to assess for metallic correlate.
via bile and feces. Erythrocyte abnormalities foreign bodies (20% of affected dogs) in the
expected with toxicity include basophilic stip- gastrointestinal tract. AUTHOR: Carrie L. Flint, DVM, DAVCP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
pling and rubricytosis in the absence of anemia.
See p. 578. Specimen Collection and Handling
Whole blood (heparinized [green top tube]
or EDTA [lavender top tube]). Refrigerated

Laboratory Tests
Left Shift

Definition increased numbers of band neutrophils (and Specimen Collection and Handling
The presence of band neutrophils (or earlier earlier precursors) are released into blood. The EDTA whole blood (lavender top tube) and
neutrophilic precursors such as metamyelocytes cause of active inflammation inducing a left freshly prepared blood smear for laboratory
or myelocytes) in peripheral blood, which shift can vary from infectious (e.g., bacterial, to stain
indicates active inflammation. It is clinically fungal) to noninfectious (e.g., pancreatitis,
useful to define the type of left shift present in IMHA) causes. Pearls
leukograms. When segmented neutrophils are • Always examine a stained blood smear for
also increased, the left shift can be described Reference Interval band neutrophils, because the neutrophil
3
as “regenerative,” suggesting an appropriate Dogs: 0-0.3 × 10 band neutrophils/mcL; cats: counts generated by automated hematol-
3
marrow response. When the segmented 0-0.2 × 10 band neutrophils/mcL ogy analyzers do not distinguish between
neutrophil count is within or below reference segmented and band neutrophils. Toxic
range, the left shift is described as “degenera- Causes of Abnormally High Levels change in neutrophils, another indicator of
tive,” suggesting the granulopoietic response Acute or active inflammation, granulocytic intense inflammation that can accompany
of marrow is outweighed by tissue demand. leukemia a left shift, is also detected only on blood
smear examination.
Physiology Next Diagnostic Steps to Consider • Although it mimics a left shift, the hypo-
Band neutrophils, metamyelocytes, and if Levels Are High segmentation of neutrophils in Pelger-Huët
myelocytes are late neutrophilic precursors that Identify source of inflammation; if none is anomaly (see p. 1371) is not considered a
normally remain in the marrow storage pool to found despite comprehensive evaluation and left shift.
differentiate into segmented neutrophils there. repeated assessments, a bone marrow aspirate
When intense tissue demand for neutrophils and core biopsy could be indicated to assess AUTHOR: Stephen D. Gaunt, DVM, PhD, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
during inflammation depletes segmented neu- for myelodysplastic syndrome or granulocytic
trophils from the marrow storage pool and/or leukemia (very rare).
induces granulocytic hyperplasia of the marrow,

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