Exam 1 lecture 1&2 Flashcards
What does Clinical pathology encompass?
- Hematology: the study of blood
- Clinical chemistry: the measurement of physiologic analytes and biochemical reactions
- Cytology: the study of cells, exfoliative or in suspension.
- Fluid analysis of non-blood fluids: urine, cavitary effusions, joint fluid, cerobrospinal fluid, etc. It incorporates automated cell counting, protein measurement, biochemical assays, and cytology.
Handling Blood Samples. Test Tubes
a. What is the color?
b. What does it contain?
c. What sample does it yield?
d. What test is it used for ideally?
- Green top tube
b. Contains Heparin (Lithium heparin) anticoagulant (good for stat samples in large animals).
c. Yields Plasma (Whereas, plasma is the liquid that remains when anticoagulant is added to prevent clotting).
d. Used for Chemistry
**Heparinized plasma differs from serum by still containing coagulation proteins (fibrinogen in high concentration in g/dL versus the rest of coagulation factors).** - Red top tube
b. No anticoagulant
c. Serum (Serum is the liquid that remains after the clotting of blood. A transparent, straw-coloured, liquid portion of the blood. An undiluted fluid, the extracellular portion of blood).
d. Chemistry, ELP (Electrophoresis). - Green tiger stripped.
b. Heparin + gel (silicon gel helps separate serum or plasma from cells after centrifugation). These are often serum or plasma separators or tiger stripped tubes.
c. Plasma
d. Chemistry - Red Plastic tube + gel (plastic tubes contain a contact activator to trigger clotting and come with or without silicon gel).
b. Silicon gel, No anticoagulant.
c. Serum
d. Chemistry, ELP - Purple top tube
b. Potassium EDTA as the anticoagulant. It is usually not centrifuged unless it is used for certain tests, such as measurement of ammonia, ACTH (Adrenocorticotropic Hormone).
c. Yields Whole Blood
d. Hematology, Cytology, Flow cytometry, Clonality (PARR), Coombs test.
- Blue top tubes
b. Citrate as an anticoagulant
c. Plasma
d. Coagulation
Which samples should be centrifuged ASAP?
Which sample test tube should not be centrifuged?
- All samples for Chemistry and Coagulation tests should be centrifuged ASAP to yield serum or plasma and not be left as whole blood.
- EDTA tubes for hematology testing should NOT be centrifuged at all and should be maintained as whole blood.
What does whole blood, plasma, and Serum represent?
Which one is used for CBCs, handheld analyzers, anesthetic monitoring?
Which one is used for benchtop biochemical testing?
Which one is used for benchtop biochemical testing and it is sometimes required?
- Whole blood: represents the an unspun, non-clotted sample, +/- anticoagulant. It is commonly sued with point-of-care handheld analyzers in urgent care, anesthetic monitoring, or field settings and for CBCs.
- Plasma: is the fluid fraction of whole blood obtained from an anticoagulant sample. It is commonly used for benchtop biochemical testing.
- Serum: is the fluid fraction of whole blood obtained from a clotted, non-anticoagulated sample. It is commonly used for benchtop biochemical testing and is sometimes required
What factors contribute to pre-analytical errors?
Give examples on how to avoid these errors
- Poor blood collection technique, storage, and submission
- Traumatic venipuncture may introduce hemolysis and/or artificially reduce platelet counts.
- Transfer blood samples quickly bc the coagulation clock is ticking
- Fill purple top tubes last if possible to avoid EDTA contamination of samples intended for biochemistry: leads to false increase in Potassium.
- Avoid plunging the syringe when filling collection tubes - allow tube to fill via vaccum pressure; excess pressure induces hemolysis
- For anticoagulant tubes, ensure proper volume and prompt, gentle tube inversion for mixing.
How can serum or plasma be store and for how long?
- They should be refrigerated or immediately processed
- Excess heat can cause erroneous values
- Freezing plasma/serum is an option; commonly used for clinical research or auxiliary test.
- CBCs samples should not be centrifuged or frozen: best run ASAP, but if refrigerated tehn brought to room temperature within 72 hours of collection need to be processed (many labs will store them up to 7 days).
**Make sure the sample is secure, cushion excess space, and waterpoof paperwork**
What color tube contains Potassium, EDTA variants and prevents coagulation by chelating calcium; and it is gentler on cells?
-Purple top tube
What color top tube inhibits coagulation by potentiating antithrombin and it is sued for plasma biochemistry?
-Green-top: Heparin anticoagulant
Which color tube top reversibly prevents coagulation by wekly chelating calcium and it is used for coagulation testing?
-Blue: Citrate
Which colot tube top is species dependent clotting time prior to centrifugation and it is used for serum biochemistry?
Plain Red top tube
What color top are serum separator tubes?
What tests use these type of tubes?
- Tiggered tops
- Contain a gel with intermediate density between cells and serum or plasma
- Upon centrifugation the fluid fraction will be separated from the cell fraction, preventing leeching of certain analytes into the cell fraction - if not using a tiger top, immediate separation of fluid from cells is necessary!
- Phenobarbital measurement test are falsely decreased from fluid fraction contact with the gel separator (check sample requirements).
What are some common serum/plasma appearance changes?
HLI: Hemolysis, Lipemia, Icterus
- Hemolysis: free hemoglobin and subsequent red discoloration, may be in vivo or in vitro intravascular hemolysis
- Lipemia: results in lactescent appearance, comon post-prandial samples and why patients should ideally be fasted for blood draw.
- Icterus: elevated bilirubin and yellow discoloration; use species specific rubrics, as large animal plasma and serum naturally have a moderate yellow appearance
**Significant HLI change may interfere with CBC and/or clinical chemistry measures**
Intravascular hemolysis interferance
What species are most affected by in vitro or in vivo hemolysis regarding chemistry blood test results?
CBC
- In vitro hemolysis decreases packed cell volume (PCV), Hematocrit (HCT), and Red Blood Cell Count (RBC).
- MCHC (mean corpuscular hemoglobin concentration) will be falsely increased (HGB proportionally higher than HCT or PVC) MCV is unaffected.
- Ghost erythrocytes from intravascular hemolysis may be falsely counted as platelets, increasing PLT
- Refractometric protein becomes difficult to read.
Chemistry
- Spectrophotometric interference and inhibition of chemical reactions
- Increase in intra-RBC analytes: Potassium (horses, camelids, Japanese dog breeds), phosphorous, ALT, LDH, Mg.
- Minimal to mild increase in creatine kinase (CK) enzymatic activity
- Electrophoresis: severe hemolysis can cause beta globulin spikes.
Interference from Lipemia
What does the blood look like when this interference is present and when the lips precipitate after refrigeration?
What also promotes in vitro hemolysis?
CBC
- Increase HGB and MCHC falsely
- Large lipid aggregates may be flasely counted as platelets
- Increse in PLT, leukocytes, WBC
- Falsely increase refractometic protein
Chemistry
- Spectrophotometric interference
- Proportional decrease in Na & Cl, and potasium
**Lipemia promotes hemolysis**
-Refrigeration allows lipid to precipitate and collection of less lipemic serum/plasma is possible
How does Icterus interfere with CBC and Chemistry?
CBC
-Little to no effect
Chemistry
-Marked to severe hyperbilirubinemia falsely decreases biruet total protein and creatinine respectively
