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1326 Coccidiodes Serology Colloid Osmotic Pressure (COP)

Specimen Collection and Handling Pearls • Cobalamin concentration within the refer-
Serum (red top tube), 1 mL, collected after • Evaluate in conjunction with folate and ence interval does not rule out intestinal
VetBooks.ir refrigerated. Freeze if greater than 24 hours • Dietary deficiency is uncommon as cobala- • Gastrointestinal diseases often respond to
trypsin-like immunoreactivity.
disease.
overnight fast; separate serum from clot. Store
min is abundant in commercial pet foods.
treatment poorly until cobalamin supple-
before testing.
Relative Cost: $$ (cobalamin only); $$$ • Although low values may be seen, assessment mentation is begun.
of cobalamin levels is no longer considered
(cobalamin and folate); $$$ (cobalamin, folate, reliable for the diagnosis of intestinal bacterial AUTHOR: Shelley Burton, DVM, MSc, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
and trypsin-like immunoreactivity) overgrowth/dysbiosis.
Coccidiodes Serology

Definition • Agar gel immunodiffusion (AGID): can Causes of Abnormally Low Levels
Coccidioides immitis is a dimorphic soil fungus detect IgM and/or IgG antibodies. False- • Uninfected animal
that is found in the lower Sonoran life zone positive results (especially at low titer) are • False-negative results: insufficient time
(Arizona, Southern California, and New Mexico common. for seroconversion, severely immuno-
in the southwestern United States and in • Latex agglutination: detects immunoglobulin compromised, other
parts of Mexico); it can cause serious illness M (IgM) that occurs early in infection. False-
in infected dogs. Serologic testing is used to help positive results common. Important Interspecies Differences
confirm suspected infection and is especially • Enzyme-linked immunosorbent assay Antibodies may persist in cats for years even
useful when cytologic samples from diseased (ELISA): cross-reactive with antibody to with therapy (dependent on assay type).
tissue are not readily available or when organism other fungi
is not visualized. ○ IgM: ≈15% false-positive; occurs early in Lab Artifacts
infection • Cross-reactivity with Blastomyces sp. is pos-
Synonyms ○ IgG: indicates chronic infection sible in ELISA tests.
Coccidioidomycosis, Valley fever Less commonly used tests: • False-negative complement fixation antibody
• Complement fixation antibody: detects IgM. test in dogs may be due to interference from
Physiology Positive in early infection anticomplement factors in 15%-25% of
Infection is acquired via inhalation of • Tube precipitation antibody: detects IgG. normal dog sera.
anthroconidia/anthrospores from soil, followed Positive with active infections and postex-
by development of pulmonary disease with posure. Titers ≥64 are seen more commonly Specimen Collection and Handling
potential dissemination to skeletal system, with severe pulmonary or disseminated Serum (red top tube), single sample or paired
lymph nodes, eyes, heart, lungs, central nervous disease. samples obtained 4-6 weeks apart. Refrigerate.
system, and other visceral organs. • Coccidioides galactomannan antigen assay: Titers can be run on cerebrospinal fluid.
poor sensitivity
Reference Interval Relative Cost: $$
Reference intervals vary among laboratories and Next Diagnostic Steps to Consider
test methodologies. Both IgG (chronic) and IgM if Levels are High Pearls
(acute) testing can be performed, as can antigen Consider confirmation with cytology or histol- • Rising titers over time may suggest poor drug
assays (less sensitive than antibody assays). ogy if feasible. Culture is not recommended, therapeutic response.
especially in a private clinical setting, as the
Causes of Abnormally High Levels organism is highly infectious to humans. See AUTHOR: Erin N. Burton, DVM, MS, DACVP
Interpretation of reported values is highly p. 184. EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
dependent on test methodology. Check with
specific laboratory.

Colloid Osmotic Pressure (COP)

Definition pressures generated both intravascularly and maintaining electroneutrality and increasing
The pressure exerted by large non-permeant interstitially. Albumin is responsible for ≈80% of plasma osmolality.
proteins that promotes intravascular fluid the colloid osmotic pressure (COP), with minor
retention and maintains blood volume. contributions from globulins and fibrinogen. Reference Interval
With normal vascular integrity, these proteins • Dog: 14-27 mm Hg
Synonym are unable to traverse the vascular membrane, • Cat: 21-34 mm Hg
Oncotic pressure preventing fluid movement to the interstitial
space. COP also stimulates intravascular fluid Causes of Abnormally High Levels
Physiology shifting through an osmotic effect, the Gibbs- Not clinically significant. Hemoglobinemia (hemo-
The movement of fluid across capillary mem- Donnan effect. As plasma colloidal proteins are lysis), recent treatment with colloid solutions (e.g.,
branes is mediated through Starling’s forces, anions, permeant cations (e.g., sodium) will plasma, Hetastarch), and hyperglobulinemia (e.g.,
which include hydrostatic and colloid osmotic readily diffuse into the intravascular space, feline infectious peritonitis, multiple myeloma)

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