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Baermann Fecal Examination



DEFINITION


A method used for microscopic evaluation of fecal specimens for parasite larvae. Rather than being drawn to the surface, as with a fecal flotation, parasites are detected after being drawn to the bottom of the Baermann apparatus. The Baermann apparatus is a funnel with a rubber tube attached to the stem, usually supported by a ring stand. Feces are put on cheesecloth in a strainer, which is placed in the funnel. Water is added to cover the specimen, which is then macerated. An aliquot of fluid collected after a few hours is examined microscopically for parasitic larvae.



TYPICAL NORMAL RANGE


Reported as negative or positive with species identification



PHYSIOLOGY


The Baermann apparatus uses the larvae’s tendency to migrate from fecal matter to warm water.



CLINICAL APPLICATIONS


CAUSES OF ABNORMALLY HIGH LEVELS: Filarid parasite (Filaroides osleri, F. milksi, F. hirthi, Crenosoma vulpis, and Aelurostrongylus abstrusus) infections are most likely to be detected by this method of fecal examination.


NEXT DIAGNOSTIC STEP TO CONSIDER IF LEVELS HIGH: Positive fecal with parasite identification is considered diagnostic.



SPECIMEN AND PROCESSING CONSIDERATIONS


DRUG EFFECTS ON LEVELS: Anthelmintics may decrease larval shedding. LAB ARTIFACTS THAT MAY INTERFERE: Test is not sensitive. A negative test does not rule out infection because fecal shedding of larvae is intermittent.


SPECIMEN: Fresh (less than 24 hours old) fecal specimen submitted in dry container.


RELATIVE COST: $$



PEARLS


Bronchoscopy is preferred for detection of F. osleri, but the procedure is time consuming, more costly, and requires general anesthesia. Baermann fecal flotation is considered to have a slight advantage over usual fecal flotation for detection of larvae in feces; no advantage for detection of ova.


AUTHOR: LOIS ROTH-JOHNSON



Bartonellosis Testing



DEFINITION


Bartonella spp. are a group of vector-transmitted, intraerythrocytic bacterial organisms that can induce persistent infections in dogs, cats, and humans.



TYPICAL NORMAL RANGE


Consult laboratory for information regarding reference ranges. Some general guidelines include:


• Immunofluorescence antibody (IFA) test for B. vinsonii and B. henselae. Negative titer is <1:64.

• Western immunoblot (FeBart) for multiple Bartonella spp. in dogs and cats. Results available as negative or +1 to +4, with +3 and +4 considered positive and +2 considered to be possibly affected.


PHYSIOLOGY


Following vector transmission, chronic intravascular infections may produce no clinical signs or cause acute, life-threatening disease or chronic debilitating illness. Cats may exhibit fever, lymphadenopathy, or central nervous system (CNS) signs. Seropositive dogs may exhibit polyarthritis, endocarditis, myocarditis, CNS signs, idiopathic pleural effusion, granulomatous disease, cutaneous vasculitis, uveitis, immune-mediated hemolytic anemia, or immune-mediated thrombocytopenia.



CLINICAL APPLICATIONS


CAUSES OF ABNORMALLY HIGH LEVELS: Seropositivity indicates exposure to Bartonella spp.


NEXT DIAGNOSTIC STEP TO CONSIDER IF LEVELS HIGH: If seropositive, consider: (1) submitting whole blood for preenrichment culture (with BAPGM) followed by PCR and subculture onto agar plates; (2) tissue biopsy for histopathologic analysis, Warthin-Starry stain; or (3) submit whole blood or 25-50 mg of fresh or frozen tissue for PCR. Speciation for B. henselae, B. clarridgeiae, B. quintana, and B. vinsonii is possible with PCR testing. Diagnosis may be difficult to confirm.


IMPORTANT INTERSPECIES DIFFERENCES: Culture may be a less sensitive method for diagnosis in dogs than in cats, but the newly introduced preenrichment culture method has greatly improved sensitivity.


CAUSES OF ABNORMALLY LOW LEVELS: In both species, cyclic bacteremia can result in false negatives for both blood culture and PCR.


NEXT DIAGNOSTIC STEP TO CONSIDER IF LEVELS LOW: Pursue additional testing techniques, repeat testing, or empirical treatment.



SPECIMEN AND PROCESSING CONSIDERATIONS


DRUG EFFECTS ON LEVELS: Effective antibiotic treatment may decrease serology titers. Use of effective antibiotics prior to sample collection may result in a false-negative culture or PCR test.


LAB ARTIFACTS THAT MAY INTERFERE: PCR: false-positive results via contamination of samples; false-negative results due to degradation of nucleic acids via improper sample handling and storage. SPECIMEN: Contact laboratory for specific instructions. IFA: submit 1 mL serum (red-top tube). Western immunoblot (FeBart): submit whole blood, serum (red-top tube), or plasma (green-top or lavender-top tube). PCR: submit whole blood collected in EDTA (lavender-top tube). Preenrichment culture with PCR: submit 2 mL whole blood collected in EDTA (lavender-top tube).


RELATIVE COST: $$ (IFA, Western blot, PCR)


AUTHOR: PATTY J. EWING



Basophils



DEFINITION


White blood cell (granulocytic leukocyte) that has a segmented nucleus and metachromatic (purple) granules in cytoplasm. Basophils are rarely encountered in the blood of healthy animals.



TYPICAL NORMAL RANGE


Dogs and cats: 0-0.1 × 103 basophils/μL.



PHYSIOLOGY


Basophilic precursors undergo differentiation in the bone marrow, enter peripheral blood circulation for a few hours, and then enter tissue. Basophils produce leukotrienes and release histamine, heparin, and other mediators from their granules. Basophils participate in immunoglobulin E-mediated hypersensitivity reactions. They are similar in morphology to mast cells, but mast cells have a nonsegmented nucleus and primarily reside in tissue.



CLINICAL APPLICATIONS


CAUSES OF ABNORMALLY HIGH LEVELS: Allergic reactions (e.g., food, insect sting); parasitism (e.g., dirofilariasis/heartworm disease, flea infestation): mast-cell neoplasm; basophilic leukemia; myeloproliferative neoplasms (e.g., essential thrombocythemia, polycythemia vera)


NEXT DIAGNOSTIC STEP TO CONSIDER IF LEVELS HIGH: Additional tests directed by history, physical exam findings, and results of ancillary diagnostic tests to rule out causes of high values listed above


IMPORTANT INTERSPECIES DIFFERENCES: The granules in feline basophils stain lavender or light violet. The metachromatic staining of granules in feline basophilic myelocytes diminishes as the basophilic precursors undergo maturation in the marrow. Because canine basophils have comparatively low numbers of metachromatic granules, a grey basophilic cytoplasm, and are large, they can be misidentifled as monocytes on blood smear.



SPECIMEN AND PROCESSING CONSIDERATIONS


SPECIMEN: EDTA whole blood (lavender-top tube) and freshly prepared blood smear


RELATIVE COST: $$ (reported as part of CBC)



PEARLS


Basophilia often accompanies eosinophilia, a further indication of allergic or parasitic disease. Careful examination is necessary to identify basophils; when stained with the rapid Romanowsky stains (e.g., Diff-Quik), the cytoplasmic granules of canine basophils may be even less apparent.


AUTHOR: STEPHEN D. GAUNT



Bence Jones Urinary Proteins



DEFINITION


Unassociated immunoglobulin light chains produced in excess by abnormal plasma cells, typically with malignant plasma cell neoplasia (multiple myeloma).



SYNONYMS


Free immunoglobulin light chains, M-proteins, myeloma proteins, paraproteinuria



TYPICAL NORMAL RANGE


Reported as negative or positive



PHYSIOLOGY


Light chains are a component of immunoglobulins. Increased production occurs with increased immunoglobulin production or catabolism, as with multiple myeloma or (rarely) plasma cell tumors, the benign counterpart. Bence Jones proteins precipitate when heated, followed by redissolving when boiled and precipitation again when cooled.



CLINICAL APPLICATIONS


CAUSES OF ABNORMALLY HIGH LEVELS: Multiple myeloma; less often associated with extramedullary plasmacytoma or chronic lymphocytic leukemia; rarely associated with chronic infectious diseases


NEXT DIAGNOSTIC STEP TO CONSIDER IF LEVELS HIGH: Confirm monoclonal gammopathy with plasma immunoelectrophoresis. Assess for osteolytic bone lesions (radiographs); bone marrow plasmacytosis or plasma cell neoplasia (cytologic analysis of aspirate, or biopsy); urine protein electrophoresis (monoclonal spike in β or d regions).



SPECIMEN AND PROCESSING CONSIDERATIONS


LAB ARTIFACTS THAT MAY INTERFERE: False positives can occur with marked proteinuria.


SPECIMEN: Urine: Store at 2○C-8○C (refrigeration).


RELATIVE COST: $$



PEARLS


Heat precipitation method is not highly sensitive. Urine protein dipstick tests do not detect Bence Jones protein. The presence of Bence Jones proteins in the urine does not indicate glomerular disease (the molecules are sufficiently small to pass through normal glomerular fenestrations).


AUTHOR: LOIS ROTH-JOHNSON


1ST EDITION AUTHOR: FONZIE QUANCE-FITCH



Bicarbonate



DEFINITION


An anion that is the major extracellular buffer in blood



TYPICAL NORMAL RANGE


Dogs and cats: 17-24 mEq/L (mEq/L = mmol/L).



PHYSIOLOGY


Bicarbonate is formed from the conversion of carbon dioxide and water to carbonic acid by carbonic anhydrase. Carbonic acid dissociates into bicarbonate and hydrogen ion. During metabolic acidosis, bicarbonate minimizes pH changes by binding to excess H+. Binding excess H+ decreases measurable Hco−3.



CLINICAL APPLICATIONS


CAUSES OF ABNORMALLY HIGH LEVELS: Metabolic alkalosis (causes: vomiting, diuretics, overadministration of bicarbonate) or respiratory acidosis (causes: pulmonary parenchymal disease [pneumonia, pulmonary edema], pulmonary restrictive disease [pleural effusion, pneumothorax, diaphragmatic hernia], hypoventilation/central nervous system depression [anesthesia, narcotics, brain stem disease], airway obstruction)


NEXT DIAGNOSTIC STEP TO CONSIDER IF LEVELS HIGH: Evaluate arterial blood gas profile (particularly pH and Pco2) to differentiate between metabolic alkalosis (high pH, high Hco−3, high Pco2) and metabolic compensation for respiratory acidosis (low pH, high Pco2, high Hco−3). Evaluate for underlying causes listed above.


CAUSES OF ABNORMALLY LOW LEVELS: Metabolic acidosis (causes: bicarbonate loss due to diarrhea, lactic acidosis, ketoacidosis, uremia, and ingestion of ethylene glycol) or compensation for respiratory alkalosis (causes: pulmonary disease [pneumonia, pulmonary edema], direct stimulation of central nervous system [pain, anxiety], septicemia)


NEXT DIAGNOSTIC STEP TO CONSIDER IF LEVELS LOW: Evaluate arterial blood gas profile to differentiate between metabolic acidosis (low pH, low Hco−3, low Pco2) and metabolic compensation for respiratory alkalosis (high pH, low Pco2, low Hco−3). Evaluate for underlying causes listed above.



SPECIMEN AND PROCESSING CONSIDERATIONS


LAB ARTIFACTS THAT MAY INTERFERE: Decrease: processing delay. Specimens analyzed within 15 minutes of collections are preferred. Storage in a capped syringe on ice at 4○C for up to 2 hours is acceptable.


SPECIMEN: Bicarbonate is a calculated value provided as part of a blood gas analysis. Whole blood in a heparinized syringe, avoiding exposure to room air, is used as described for blood gas analysis.


RELATIVE COST: $$ (part of blood gas analysis, not available as a separate test)



PEARLS



• Total carbon dioxide (Tco2) estimates plasma bicarbonate, which is part of most serum biochemistry profiles. Tco2 is the total amount of co2 gas that can be released from serum.

• At physiologic pH (7.4), about 95% of the potential gas is co2 and 5% is Hco−3. Therefore, although Tco2 is usually slightly higher (1-2 mEq/L) than bicarbonate on a blood gas profile, it is considered a clinically accurate assessment of bicarbonate.

• May not be practical to submit to a reference laboratory, owing to sensitivity of specimen to environmental influences and time constraints for accurate test results

AUTHOR: LOIS ROTH-JOHNSON


1ST EDITION AUTHOR: JAMES H. MEINKOTH



Bile Acids (Blood, Urinary)



DEFINITION


Family of detergent-like compounds (predominately cholic acid and chenodeoxycholic acid) synthesized in the liver from cholesterol and secreted in bile to aid in digestion and absorption of fat and fat-soluble vitamins.



TYPICAL NORMAL RANGE



• Fasting bile acids normally <5 mmol/L

• Fasting bile acids >20 mmol/L, postprandial samples >25 mmol/L, and/or urine bile acid/creatinine ratio >7.1 indicate liver disease.

• Urine: urine sulfated bile acids (USBA)/creatinine (crt) and total BA: crt are considered diagnostically useful.

• Dogs: USBA:crt > 1.0 and total BA:crt > 7 suggest liver disease

• Cats: USBA: crt > 2.0 and total BA:crt

> 4 suggest liver disease



PHYSIOLOGY


Bile acids are stored in the gallbladder; released as a bolus into the small intestines upon feeding. In health, an efficient enterohepatic circulation exists, and up to 95% of bile acids are recycled via this cycle. Serum bile acids are evaluated in paired samples (fasting, postprandial). When portal blood clearance or biliary excretion is impaired, urinary excretion of BA increases. Urinary bile acid/creatinine ratios reflect an average serum bile acid concentration. Only a single urine sample is required.



CLINICAL APPLICATIONS


CAUSES OF ABNORMALLY HIGH LEVELS: Decreased clearance from blood (decreased functional liver mass, compromised portal circulation [congenital or acquired portosystemic shunt]). Cholestasis due to obstruction, cirrhosis, inflammation. Specific causes are many.


NEXT DIAGNOSTIC STEP TO CONSIDER IF LEVELS HIGH: Assess for cholestasis (bilirubin, alkaline phosphatase), portosystemic shunt (imaging), other liver diseases (alanine aminotransferase, imaging, liver biopsy).


CAUSES OF ABNORMALLY LOW LEVELS: Low bile acid values are not clinically significant.



SPECIMEN AND PROCESSING CONSIDERATIONS



LAB ARTIFACTS THAT MAY INTERFERE



• Decrease: hemolysis, lipemia (spectrophotometric method), no effect on radioimmunoassay

• Increase: hypertriglyceridemia (spectrophotometric method), no effect on radioimmunoassay


SPECIMEN



• Serum (red-top tube): 12-hour fasting sample and 2-hour postprandial sample recommended separate serum from red blood cells as soon as possible. Store at 2○C-8○C (refrigeration).

• Urine: fresh urine, avoid blood contamination.

RELATIVE COST: Serum (single), $$ serum (paired), $$; urine bile acid/crt, $$



PEARLS



• If cholestasis is present (e.g., patient is icteric without evidence of hemolysis), bile acids do not provide any additional information on hepatic function. Bile acids are a good indicator of hepatobiliary function but are not specific for the type of underlying disease.

• Extrahepatic disorders (e.g., gastrointestinal disease) can elevate bile acid concentrations.

• Urine bile acids are more specific for canine liver dysfunction than serum bile acids.

• Occasional preprandial values that exceed postprandial values are attributed to spontaneous gallbladder contraction.

• Urine test has low diagnostic sensitivity (false negatives common) but good specificity (few false positives).

AUTHOR: LOIS ROTH-JOHNSON


1ST EDITION AUTHOR: FONZIE QUANCE-FITCH



Bilirubin



DEFINITION


A pigment produced by the degradation of the heme portion of hemoglobin (and to a lesser extent, other porphyrin-containing compounds)



TYPICAL NORMAL RANGE



• Dogs: approximately 0-0.3 mg/dL

• Cats: approximately 0-0.1 mg/dL.

• Specific values vary among laboratories.

• For mmol/L, multiply mg/dL × 17.1.


PHYSIOLOGY


During the breakdown of red blood cells (either senescent or pathologic hemolysis), heme is split to iron and protoporphyrin; protoporphyrin is converted to biliverdin then to unconjugated bilirubin predominately in macrophages of the spleen, bone marrow, and liver. Unconjugated bilirubin is released into the circulation, where it is bound to carrier proteins (albumin, globulins) and transported to the liver for uptake, conjugation, and secretion into bile. Conjugation renders bilirubin water soluble. Laboratory assays include total serum bilirubin, direct (conjugated) bilirubin, and indirect (unconjugated) bilirubin, which is a calculated value.

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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on B

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