Clinical Pathology Flashcards
Clinical Pathology
The practice of pathology as it pertains to the care of patients
The development, application and interpretation of laboratory procedures for:
○ Establishing a diagnosis and/or prognosis
○ Monitoring of treatment in sick animals
○ Monitoring animal health
What does clinical pathology involve?
Haematology
Clinical biochemistry
Cytology
Types of clinical pathology samples
Blood, serum, plasma
Urine
FNAs
Effusions
Cerebrospinal fluid
Lavages (BAL)
Synovial fluid
What is anatomic pathology?
Surgical pathology - histopathology
Necropsy
Which anti-coagulant should you use for haematology? (blood cytology)
EDTA
(Li-hep whole blood in exotics)
Which anti-coagulant should you use for clinical chemistry? (electrolyte levels)
○ Serum
○ Li-heparin plasma
○ EDTA plasma (rarely)
Which anti-coagulant should you use for measuring glucose?
Fluride-oxalate
Which anti-coagulant should you use for measuring haemostasis/coagulation?
Citrate
Which anti-coagulants work by holding onto calcium to stop the coagulation cascade?
EDTA - irreversible
Oxalate
Citrate - reversible so used to study coagulation
What is serum?
Whole blood that has been allowed to clot then centrifuged
Fibrinogen converted to fibrin and becomes part of clot so not present in serum
What is plasma?
Heparin prevents clot from happening
Centrifuged to separate liquid from cellular component
Fibrinogen not activated so present in plasma
What will happen is a biochemistry sample is contaminated with K-EDTA
False low calcium
False high potassium
Some enzymes (ALP) depend on cofactor which is taken out by EDTA
What is a normal draw/fill order?
Citrate tube first to prevent any clotting
Bacterial samples next to prevent contamination
EDTA later to reduce contamination with chemistry samples
Effects of haemolysis on results
Causes false increases in plasma/serum values of some compounds
[This is due to higher concentration from lysed RBCs]
○ Creatine kinase
○ Phosphate
○ Potassium in some species
Interferes with colorimetry - false values due to different absorbance levels
How can you avoid haemolysis
Choose appropriate gauge needle
Never dispense blood sample through needle - just syringe
Lipemia
High concentration of emulsified fat in the blood
Effects of lipemia on results
Can increase or decrease values of some compounds in serum/plasma
Presence of extra lipid fractions causes false low values of electrolytes (less aqueous content)
Turbidity interferes with light detection methods - false results for colorimetry (increased refraction)
Icterus
High levels of bilirubin in blood (jaundice)
Which species has naturally higher bilirubin?
Horses
Effects of icterus on results
Gives false results for colorimetry
Pre-analytical sources of variation and errors in lab results
Patient preparation
E.g. Not fasted patient
Sample preparation
E.g. Choice of collection tube
Shipping
Analytical sources of variation and errors in lab results
Appropriate equipment/reagents (Validated)
Still working (QC)
Post-analytical sources of variation and errors in lab results
Results to the right place for the right patient
Appropriate interpretation
Diagnostic sensitivity and specificity
Control of analytical variation
Validation of the techniques used
○ Assay parameters
○ Machine setup
○ Analytical range
○ Must be known before analysis starts
Quality control:
○ Must be performed regularly before and/or during routine analysis
○ Only know the equipment was working when the last QC passed
