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Clinical Pathology > Biochemistry Profiles & Analyzer Methodologies > Flashcards

Biochemistry Profiles & Analyzer Methodologies Flashcards

1
Q

What ate the 3 major veterinary laboratory disciplines?

A
  1. clinical pathology - hematology, coagulopathy testing, clinical biochemistry, urinalysis, fluid analysis, cytology
  2. anatomical pathology - histopathology, biopsy, necropsy
  3. other - bacteriology, virology, mycology, immunology, parasitology
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2
Q

What are 3 goals of clinical biochemistry?

A
  1. identify the organs involved
  2. create a differential diagnosis list with a top differential that explains all findings in the case
  3. guides to a decision of what to do next, like re-examine, obtain more history, extra testing, etc.
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3
Q

Serum enzymes:

A
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4
Q

What is used as a control for serum protein electrophoresis?

A

cellulose acetate strip and densitometer tracing

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5
Q

What are 4 pros and 3 cons of in-house testing?

A

PROS
1. immediate results for point-of-care testing
2. customer service
3. additional diagnostics
4. time-sensitive results with fresh samples

CONS
1. investment for equipment ($$$)
2. maintenance cost
3. inventory availability

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6
Q

What are the 3 sources of error with in-house testing?

A
  1. PRE-ANALYTICAL - prior to analysis; sample selection, collection technique, preservation/management
  2. ANALYTICAL - analyzer error; miscalibration, internal/external QC personnel training, following SOPs
  3. POST-ANALYTICAL - errors in transcription or interpretation of results
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7
Q

When is it most beneficial to collect samples?

A
  • before treatment
  • with a fasted patient
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8
Q

What should be avoided when sending out samples?

A

shipping fresh cytology with formalin-fixed tissues

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9
Q

What are 6 common samples collected for clinical pathology?

A
  1. blood - whole, serum, plasma
  2. bone marrow
  3. body fluids - pleural, peritoneal, pericardial, semen, lymph, CSF
  4. washes - tracheal, bronchial
  5. tissue samples - aspirates, impressions, scraping, brushes
  6. urine, feces, milk
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10
Q

How are anticoagulants used for clinical pathology samples? In what 3 situations do they tend to not work as directed?

A

used to prevent blood from clotting and expedites transfer samples into anticoagulants following collections

  1. collection is too slow
  2. tissue fluid is collected with blood
  3. sample not adequately mixed
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11
Q

What is the purple top tube? What is it most commonly used for? What can it also be used for?

A

EDTA - anticoagulant

hematology/CBC

cytology of fluids - keeps high protein fluids, like abdominal/thoracic fluids, prostatic fluids, and tracheal/bronchial fluids, from coagulating

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12
Q

What tube is preferred for bird and reptile hematology/CBC? Why?

A

green top heparin tubes

EDTA will lyse their RBCs

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13
Q

What is recommended to also submit with EDTA purple top tubes? How much should these tubes be filled?

A

freshly made (unstained) blood smear to optimize examination of RBC, WBC, and platelet morphology

at minimum halfway, since excess EDTA can alter results

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14
Q

What is the green top tube? When is it most commonly used?

A

heparin tube containing the naturally occurring mucopolysaccharide that potentiates action of antithrombin III to inhibit clotting factors

STAT clinical biochemistry or whole blood, since other anticoagulants bind calcium and would alter electrolytes

  • NOT prefered anticoagulant for hematological analysis, unless in bird and reptile patients
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15
Q

What is another option if STAT biochemistry is needed, but a heparin tube is not available?

A
  • centrifuge and transfer plasma to red top tube
  • refrigerate until use
  • warm to room temperature before analysis
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16
Q

What is the blue top tube? What is it most commonly used for?

A

contains sodium citrate, which reversibly chelates calcium

coagulation assays and platelet function studies

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17
Q

What is the preferred ratio of blood to be collected in a sodium citrate tube?

A

1 mL of sodium citrate per 9 mL of blood

  • 1 tube requires 9 mL of blood
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18
Q

What is the red top, or plain, tube? What is it most commonly used for?

A

contains no additive, allowing the sample to clot and getting serum upon centrifugation

biochemistry tests and serology

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19
Q

Why are the red top tubes not used for STAT biochemistry?

A

time to clot is variable and it typically requires more than 20 mins to clot

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20
Q

What 3 specific tests require the use of a red top tube?

A
  1. serum bile acids
  2. serum protein electrophoresis
  3. trypsinogen-like immunoreactivity
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21
Q

What is the tiger top tube? What is achieved upon centrifugation?

A

tube containing a gel matrix that promotes efficient clotting and avoids altering biochemical parameters by leakage/metabolism from cells

serum containing less calcium, no fibrinogen, no clotting proteins, and some active complement proteins

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22
Q

What is the difference between plasma and serum?

A

PLASMA has anticoagulants, allowing it to contains clotting proteins and fibrinogen

SERUM is the result following coagulation, so it has no clotting proteins or fibrinogen

23
Q

How does the concentration of ions compare in plasma and serum?

A

plasma has slightly greater calcium and slightly less potassium compared to serum

24
Q

Why is EDTA inappropriate for biochemistry?

A

alters samples, falsely increasing calcium and potassium and decreasing magnesium

25
Q

Why is serum preferred for electrophoresis and biochemistry?

A

does not contain fibrinogen that can interfere with results

26
Q

EDTA vs Serum tube:

A
27
Q

What are the preferred gauges of needles used on the different sizes of patients? Why is it important to use the correct needle size?

A
  • SMALL BREED up to 10 kg = 25g
  • MEDIUM BREED 10-30 kg = 22g
  • LARGE BREED 30-60 kg = 20g
  • GIANT BREED over 60 kg = 18 g

avoids hemolysis and compliments blood vessel sizes

28
Q

How should blood samples be transferred into sample tubes?

A
  • closed system (butterfly) and vacutainer = directly dispense through needle
  • otherwise, remove the needle and dispense slowly into the sample tube

avoids hemolysis

29
Q

What is the correct order of filling samples for blood panels?

A
  1. blue top (sodium citrate)
  2. red top (serum)
  3. greed top (heparin)
  4. purple top (EDTA)
30
Q

How should samples contained with EDTA and heparin be handled to ensure even disbursement of the anticoagulant?

A

gentle invert 10-15 times and used within 3-4 hours or 1 hour

31
Q

What are 3 common problems with test results due to sample quality? How can they be avoided?

A
  1. HEMOLYSIS - broken RBCs distort analyte values, making plasma/serum pink
  2. LIPEMIA - milky plasma/serum filled with lipids interferes with chemical reactions and light absorption
  3. ICTERUS - excessive bilirubin pigments makes plasma/serum yellow

have pets fasted for 4-6 hours prior to appointment

32
Q

What are the 2 classifications of samples sent to commercial labs? What packaging scheme is required for transit?

A
  1. Category B, biological substances - includes diagnostic samples from animals
  2. Category A, infectious substances - includes samples tested for more serious animal diseases that may cause disability or fatality in humans exposed to the contents

triple layer

33
Q

What are 2 important characteristics of commercial secondary containers for veterinary samples?

A
  1. pouch in the back for paperwork separate from sample
  2. absorbent material placed in the pouch

biohazard labels must not be added to the outer container

34
Q

What analytical method do most chemistry analyzers use? What commonly interferes with sample detection?

A

spectrophotometry

colored substances alter light absorption and reflection

35
Q

What is spectrophotometry?

A

analytical chemistry technique that uses light broken down into many wavelengths (spectrum) of light to measure concentrations of analytes present in the serum

36
Q

What are the 2 most common spectrophotometers used?

A
  1. ABSORBANCE - wet chemistry in veterinary laboratory
  2. REFLECTANCE - dry chemistry in house
37
Q

How does absorbance spectrophotometry work?

A

WET CHEMISTRY

  • light moves through a solution and is absorbed and measured
  • wavelength of light are absorbed and reflected, depending on the substrate
  • specific wavelengths are used to optimize results
38
Q

How does reflectance spectrophotometry work?

A

DRY CHEMISTRY

  • blood and a carrier is placed on a slide
  • sample is subjected to light, which is reflected and measured
  • intensity of reflection is analyte specific
39
Q

What concept is absorbance spectrophotometry dependent on?

A

Beer’s Law - absorbance and concentration have a linear relationship (higher absorbance = higher concentration)

40
Q

Icterus, hemolysis, lipemia:

A
41
Q

In what 2 ways can lipemia affect samples? How can this be avoided?

A
  1. interferes with passage of light, altering many biochemical tests
  2. acts as a detergent on RBC membrane, enhancing hmolysis

have patients fasted for 12 hours prior to blood collection

42
Q

What 5 specific effects does lipemia have on biochemistry results?

A

increased…

  1. lipase (10-20%)
  2. ALT (45%)
  3. AST (20%)
  4. LDH (50%)
  5. glucose, creatinine, bilirubin
43
Q

What naturally causes lipemia in vivo? 4 pathological causes?

A

posprandal

  1. pancreatitis
  2. diabetes mellitus
  3. equine hyperlipidemia
  4. hypothyroidism (decreased metabolism)
44
Q

What causes hemolysis of samples? What effect does this have on biochemical tests?

A

turbulence and RBC trauma at sampling

releases intracellular substances from RBCs, like AST and potassium, causing falsely increased serum potassium levels

  • also moderately changes ALP, TP, calcium, albumin, bilirubin, ALT, and CK
45
Q

In what 2 ways does bilirubin affect biochemistry results? When can this not be avoided?

A
  1. decreased creatinine
  2. increased bilirubin

if the animal is hyperbilirubinemic

46
Q

What are 4 common causes of bilirubinemia in vivo?

A
  1. hemolytic disorders
  2. fasting in horses and ruminants
  3. cholestasis (pre or post-hepatic)
  4. hepatic diseased causing decreased functional mass
47
Q

Why is it important to state any treatment an animal is receiving on a laboratory form?

A

some drugs can interfere with certain tests

48
Q

CASE: 3 y/o Scottish Terrier presents for annual PE and wellness testing. Apparently healthy at home, good energy and appetite, and no current meds. PE shows BAR, TPR WNL, and overall unremarkable. CBC also unremarkable.

What is likely the cause of the significant findings in the biochemistry profile?

A

likely blood was collected in the improper tube for biochemistry serum —> EDTA will bind to Ca+ and make it unable to participate in the clotting process and increase K+

at these levels, hypocalcemia would present with shivering, seizures, muscle fasciculations, joint pain, and tachyarrhythmia, while hyperkalemia would present with bradyarrhythmia and generalized muscle weakness

49
Q

How would collection of blood from a purple-top or blue-top tube alter biochemistry results?

A

EDTA –> chelates Ca+ = decreased Ca+ and increased K+

citrate —> decrease Ca+, no effect on K+

50
Q

CASE: 5 y/o CM Boxer presents for annual PE and wellness testing. Apparently healthy at home, good energy and appetite, no current meds. PE shows BAR, TPRR WNL, and is overall unremarkable. CBC is WNL.

Upon first collection, there are some discrepancies with the biochemistry panel. A second test was done and all analytes were WNL. What likely caused the odd results?

A

hemolysis of the sample caused the contents of the RBC, like ALT and K+ to release, increasing their values, and falsely increased ALP

51
Q

What is method validation?

A

assays (reagents and instruments) used for veterinary diagnostics are usually produced for the human market, so they must be validated to ensure they are accurate for animals

  • for example, bromocresol green (V) or bromocresol purple (H) albumin assays are not accurate for animal diagnostics
52
Q

What is the difference between accuracy and precision?

A

ACCURACY = ability to give correct results; closeness of the result to the true value

PRECISION = ability of an assay to give the same result when the test is repeated multiple times, independent of accuracy, commonly states as a coefficient of variation

53
Q

What quality assurance can be done at the pre-analytical, analytical, and post-analytical stages?

A

correct identification, appropriate samples, appropriate quality

valid method, calibration, control samples, external samples

interpretation, transcription

54
Q

How is quality assurance done?

A
  • known control samples are used daily (internal QA)
  • unknown samples are provided by QA groups to compare results to a group mean
  • results are plotted to follow trends

(question all odd results!)

Clinical Pathology (33 decks)

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