Clinical Pathology Flashcards
Principles
Reference laboratories vs in clinic laboratories (including pros and cons of each)
Reference: Used to assess non-life threatening conditions. Pros (3) - 1. More reliable results 2. More analytes tested 3. Interpretation provided. Cons - Longer turnaround for results
In clinic: Used to assess life threatening conditions, eg. electrolyte abnormalities (K+, Ca2+, Na+), Hypoglycaemia (collapse, seizures), Marked anaemia, Thrombocytopaenia. Pros (2) - 1. Rapid diagnosis 2. More profitable for practice. Cons (3) - 1. Relies on self-interpretation 2. Less variability 3. More expensive for client
Principles
Variability
a) Random inherent variability
b) Inter-animal biological variability (young animals, older animals, greyhounds)
a) Less variability - analytes under homeostatic control (glucose, K+, Ca2+), Increased variability - liver enzymes, proteins
Principles
a) What does it mean if a patient’s values are outside the reference interval
b) What can result in a healthy animal having results outside the reference interval
a) Results are abnormal
b) Biological variability (age, breed, analytes)
Principles
For each of the following, what type of test tube are samples taken in
a) Haematology
b) Coagulation
c) Biochemistry/Endocrinology
d) Ionised Ca2+/ Urgent Biochemistry
e) Glucose
f) Cardiac troponins/Phenobarbitone
Biochemistry
Describe the following biochemical analyses, icluding samples that cannot be used
a) Photometric/Colorimetric
b) Electrochemistry
c) Turbidimetric
d) Electrophoresis
Biochemistry
Sample Quality pre-analytical errors (serum colour, cause, assay interference)
a) Haemolysis
b) Lipaemia
c) Icterus
Biochemistry
Sample handling pre-analytical errors (effects on biochemistry profile)
a) Delayed sample separation
b) EDTA contamination
c) Young patient
d) Stress/excitement
e) Steroids
f) Potassium Bromide (drug)
g) Phenobarbitone (drug)
Biochemistry
Biochemical markers of damage and function ( damage markers and dysfunction markers for each body system)
a) Renal
b) Hepatic (hepatocellular)
c) Hepatic (biliary)
d) Pancreas
e) Heart
f) Muscle
g) Small intestine
Biochemistry
Renal function markers
- Kidneys are responsible for the excretion of nitrogenous waste
- Renal disease will lead to reduced renal function and glomerular filtration rate
- Accumulation of nitrogenous waste (urea and creatinine) indicates decreased excretory function of the kidney
- But remember that dehydration can cause increased urea and creatinine
- Azotaemia only occurs when over 3/4 of renal function is lost
Biochemistry
Muscle damage markers
a) Creatinine kinase (CK)
b) AST
a) Most specific marker of myocyte damage. Peak serum CK at 4-6 hours post damage. Normal serum CK after 24-48 hours post damage
b) Monocyte and hepatocyte damage. Long half life (12 hours)
Biochemistry
Causes of hyperglycaemia (4) and examples
Biochemistry
Causes of Hypoglycaemia (5) with examples (and state concentration indicating hypoglycaemia)
< 3mmol/L
Biochemistry
Causes of hyperlipidaemia (4) with examples
Biochemistry
Urinalysis
a) Why useful
b) Urine specific gravity
c) Dipstick test
d) Sediment exam
a) Important measure of renal function
Plasma proteins and calcium
a) What are most serum proteins produced by (what are the exceptions)
b) Two types of serum protein
c) Methods of measuring plasma proteins (3) + advantages and causes of error for each
a) Hepatocytes (except for immunoglobulins)
b) Albumin (half life in dogs - 8 days, half life in cattle - 2-3 weeks) and globulins (all proteins except albumin)
Plasma proteins
Disorders of serum proteins - Selective hypoalbuminaemia
4 main causes and examples of what leads to these
Plasma proteins
Disorders of serum proteins - Non-selective hypoalbuminaemia
Main causes (3) and examples
Plasma proteins
Systemic infalmmation - acute phase proteins seen in
a) Dogs
b) Cats
c) Cattle
d) How long for them to increase
e) What can use of steroids lead to
f) What can dehydration lead to
a) CRP
b) SAA, AGP
c) SAA
d) 24 hours
e) Hyperalbuminaemia
f) Hyperproteinaemia
Plasma proteins
Disorders of serum proteins - Selective hypoglobulinaemia
a) Cause
b) How to diagnose (4)
a) Failure of passive transfer (suckling)
b) 1. Zinc sulphate turbidity test
2. Serum GGT
3. Plasma [total protein]
4. Radial immunodiffusion assay
Calcium
Describe calcium homeostasis
Calcium
Causes and related pathologies of
a) Pseudo-hypercalcaemia (2)
b) Hypercalcaemia (5)
Calcium
Causes and related pathologies of
a) Pseudo-hypocalcaemia (3)
b) Hypocalcaemia (5)
Calcium
a) Correction of hypercalcaemia (4)
b) Correction of hypocalcaemia (2)
a) 1. IV fluid therapy 2. Bisphosphonate or Calcitonin treatment 3. Loop diuretics 4. Identify root cause
b) 1. Calcium gluconate (IV) 2. Identify root cause
Electrolytes
Describe sodium homeostasis
Electrolytes
Sodium imbalances - Hyponatraemia
- causes
- related pathologies leading to the causes
Electrolytes
Sodium imbalances - Hypernatraemia
- Causes
- Related pathologies leading to the causes
- treatment
Treatment: IV fluid therapy, but do not correct faster than 0.5 mmol/L/hr due to risk of cerebral oedema
Electrolytes
Hypoadrenocorticism (Hyponatraemia)
a) Signalments (1)
b) Clinical signs (4)
c) Pathology (3)
Ketonuria (Hyponatraemia)
d) Causes of ketonuria (2)
Sodium abnormalities
e) Associated clinical signs
a) Females predisposed
b) 1. Intermittent vomiting and diarrhoea 2. Lethargy 3. Abdominal pain 4. Weight loss / anorexia
c) 1. Immune mediated destruction of adrenal glands 2. Reduced cortisol production 3. Reduced aldosterone production -> low serum [Na+], high serum [K+]
d) 1. Negative energy balances causing a shift in energy production from carbohydrates to lipids 2. Diabetes mellitus
e) Associated with neurological signs (weakness, depression, seizures)
Electrolytes
Chlorine renal reabsorption
Complete the table
Electrolytes
What happens to Cl- when
a) HCO3- increases
b) Na+ increases
c) Acidosis
d) Alkalosis
a) Cl- decreases
b) Cl- increases
c) Cl- excreted with H+ in distal tubule
d) Cl- reabsorbed and HCO3- excreted in distal tube
Electrolytes
Chloride imbalances
Complete the table
Electrolytes
a) Potassium functions (4)
b) Clinical signs of hyperkalaemia (2)
a)
- Regulation of intracellular osmolarity
- Concentration gradient across the cell membrane establishes resting membrane potential
- Essential for excitable cell function (e.g. nerves, myocardium)
- Cardiac pacemaker potential – sinoatrial node pace maker function
b) 1. Bradycardia 2. Weakness
Electrolytes
a) Emergency treatment of hyperkalaemia (4)
b) Most commum cause of hyperkalaemia result, and reasons for this (3)
a) 1. Calcium gluconate to reduce bradycardia and stabilise cardiac membrane 2. Frusemide
3. IV fluid therapy (dilution) 4. Remove urinary obstruction (catheterise)
b) Most common cause is pseudo-hyperkalaemia
1. Thrombocytosis (clotting) in blood sample
2. Delayed serum separation +/- haemolysis
3. EDTA contamination (expect low Ca2+)
Electrolytes
a) Clinical signs of hypokalaemia (2)
b) Treatment of hypokalaemia and cautions
a) 1. Weakness 2. Cervical retroflexion in cats
b) Potassium chloride/gluconate fluid -> If you give concentrated K+ can lead to cardiac arrest!!
Electrolytes
a) Causes of hyperkalaemia (not pseudo!)
b) Causes of hypokalaemia
a) Increased K+ intake -> dietary excess, IV infusion overdose
Reduced K+ output -> Urinary tract obstruction, end-stage renal failure, hypoadrenocorticism
b) Decreased K+ intake -> malnutrition, diarrhoea
Increased K+ output -> Polyuria - chronic renal failure, Hyperadrenocorticism, Diarrhoea, Vomiting, Sweating (heat stroke, colic)
Electrolytes
Phosphate imbalance
Complete table
Haematology
What is the normal total protein (TP) value (g/dL) and packed cell volume (PCV) value (%) for the following
Haematology
Describe what is found in the following microhaematocrit layers (post-centrifugation)
a) Plasma
b) Buffy coat
c) Haematocrit
a) Water, proteins, nutrients, hormones
b) White blood cells, platelets
c) Red blood cells
Haematology
Interpretation of PCV and TP results
Complete the table
Haematology
Haematology analysers - Impedance analysers
a) How do they work
b) Sources of error (3)
a) Cells pass through an electric current which interferes with the flow of current, creating a pulse. Pulse height = MCV. Pulse frequency = RBC & platelet count. WBC measured after RBC lysis
b) 1. Large platelets (eg cavalier king charles spaniels, cats) can cause falsely increased RBC and decreased MCV. 2. WBC count will be falsely increased if nucleated red cells are present after lysis. 3. Three part leujocyte differential count is often inaccurate
Haematology
Haematology analysers
a) Describe how flow cytometric based analysers work
b) Describe how quantitative buffy coat analysers work
a) Stream of cells passed through laser beam to produce scatter. Fluorescent dye added to stain nucleic acids and organelles. High angle/ side scatter correlates with cell granularity. Can identify RBCs, platelets and leukocytes
b) Blood drawn into microhaematocrit tube and centrifugal force used to separate RBCs, granulocytes, agranulocytes and platelets into layers. Thickness of layer = concentration
Cytological interpretation
When examining a cytology slide, what is evidence for inflammation (3)
- Presence of neutrophils and other WBCs
- Degenerative changes to neutrophils (in tissue samples)
- Intracellular bacteria or infectious organisms
Cytological interpretation
Types of cells on a cytology slide
Complete the table
Cytological interpretation
a) What are the criteria of malignancy (5)
b) Progression from normal to malignant neoplasia
a)
1. Pleomorphism - variation in cell size (anisocytosis), variation in nuclear size (anisokaryosis), macrocytosis and macrokarycosis
2. Increased nuclear:cytoplasmic ratio
3. Nucleolar changes - multiple prominant nucleoli, variation in nucleolar size and shape, macronuclei (>1x RBC diameter
4. Multinucleation
5. Abnormal mitotic figures
Cytological interpretation
Exceptions to the criteria of malignancy (4)
- Inflammation can resemble neoplastic changes
- Damaged cells - cytoplasm isn’t visible, nuclear chromatin looks pale pink, prominent nucleoli
- Malignant tumours that appear cytologically benign - anal sac adenocarcinoma, thyroid neoplasia, adrenal neoplasia
- Lymphoma - monomorphic population of large lymphocytes, pleomorphism is a featur of reactive lymphoid hyperplasia (non-neoplastic)
Body cavity effusions
Normal body cavity fluid features
Complete the table
Body cavity effusions
Describe mesothelial cells
- Form a monolayer of specialised pavement-like cells that line the body’s serous cavities and internal organs
- Medium sized, round to ovoid cells with distinct/fringed cytoplasmic borders
- Medium sized nucleus
- Pink glucocalyx ‘halo’
Body cavity effusions
Transudate effusion
a) Meaning
b) Nucleated cell count
c) Cell isolates in sample (3)
d) Protein in sample
e) Cause
f) Pathology (4)
Body cavity effusions
Modified transudate effusion
a) Meaning
b) Nucleated cell count
c) Cell isolates in sample
d) Protein in sample
e) Cause
f) Pathology (2)
Body cavity effusions
Exudate effusion
a) Nucleated cell count
b) Cell isolates in sample (3)
c) Protein in sample
d) Causes (2)
e) Pathology (2)
Body cavity effusions
Chylous effusion
a) Meaning
b) Nucleated cell count
c) Cell isolates in sample
d) Protein content of sample
e) Causes (2)
f) Pathology (8)
Body cavity effusions
Non-chylous effusion
a) Meaning
b) Nucleated cell count
c) Cell isolates in sample
d) Protein content of sample
e) Cause
f) Pathology (2)
Body cavity effusions
Haemorrhagic effusion
a) How can it be distinguished between other effusions
b) Cytological features (2)
c) Pathology
a) If effusion > 3% PCV
b) 1. Erythrocytes without platelets (rules out contamination) 2. Erythrophagia (macrophages phagocytose RBCs)
c) Neoplasia
Body cavity effusions
Urine leakage effusion (uroperitoneum)
Defining features (2)
- Exudative / protein rich transudate
- [K+] and [creatine] in fluid is > 2x that of serum concentrations
Body cavity effusions
Causes of effusions (5)
- Increased vascular hydraulic pressure
- Decreased vascular oncotic pressure
- Increased vascular permeability (eg inflammation)
- Decreased lymphatic drainage (eg obstruction)
- Leakage of visceral contents (eg bladder, intestines, gall bladder)
Body cavity effusions
Feline Infectious Peritonitis
a) Describe what this is
b) What is seen in the effusive form
a) Immune-mediated disease triggered by infection with FCoV (feline coronavirus)
b) Immune-complex vasculitis in effusive ‘wet’ FIP causes pleural and peritoneal effusions. Effusion has very high protein (> 45 g/L) and often low nucleated cell count
Joint fluid
a) Properties of normal joint fluid
b) Sampling of joint fluid requirements
a)
- clear to straw colour
- normal joints yield a few drops
- more than this suggests effusion
- thixotropy (less viscous when shaken)
b)
- glass slide
- EDTA tube
- plain tube
- meat broth or blood culture bottle
Joint fluid
Complete the table on arthropathies
Joint fluid
Degenerative arthropathy causes of pathology (4)
- Osteoarthritis
- Osteochondrosis
- Trauma
- Joint instability
Joint fluid
Inflammatory arthropathy
a) Infectious pathologies (4)
b) Non-infectious pathologies (4)
a)
- Borrelia burgdorferi (spirochetes)
- Anaplasma phagocytophilium (ricketssial)
- Leishmania infantum (protozoal)
- Bacterial
b)
- Immune mediated polyarthritis (IMPA)
- Shar-Pei and other breed-associated polyarthritis
- Systemic Lupus Erythematosus
- Rheumatoid Arthritis
Joint fluid
Septic arthritis pathology (3)
- Trauma associated or haematological spread
- Solitary joint involvement most common, but haematological spread can involve multiple joints
- Bacterial culture is poorly sensitive
CSF
Albuminocytological dissociation in CSF findings
a) Appearance
b) Protein compared to normal
c) Nucleated cell count
d) Cytology
a) Clear
b) Increased
c) < 5 cell/μL
d) Lymphocytes and monocytoid cells
CSF
Healthy CSF findings
a) Appearance
b) Protein
c) Nucleated cell count
d) Cytology
a) Clear
b) < 0.3g/L when sampled cisternal, < 0.45g/L when sampled lumbar
c) < 5 cells/μL
d) Lymphocytes and monocytoid cells
CSF
Neutrophilic pleocytosis in CSF findings
a) Appearance
b) Protein compared to normal
c) Nucleated cell count
d) Cytology
a) Abnormal
b) Increased
c) > 5 cells/μL
d) Up to >100 neutrophils per μL
CSF
Mononuclear pleocytosis in CSF findings
a) Appearance
b) Protein compared to normal
c) Nucleated cell count
d) Cytology
a) Abnormal
b) Increased
c) > 5 cells/μL
d) Elevated number of lymphocytes and monocytoid cells
CSF
Analysing CSF
a) Sampling technique
b) Considerations of collecting CSF
c) How are nucleated and red cell counts determined
a) General anaesthesia, sterile technique
b)
- EDTA tube for cell count
- plain tube for culture
- cells in CSF lyse rapidly due to low protein concentration
- cell count and cytology prep needs to be done 30-60 minutes
c) Haemocytometer used to count number of cells per μL
CSF
Neutrophilic pleocytosis - Steroid response meningitis arteritis (SRMA) vs bacterial meningitis
a) Age of dogs affected with SRMA
b) Breeds predisposed to SRMA
c) Symptoms of SRMA
d) Neutrophil status in SRMA
e) Neutrophil status in bacterial meningitis
f) Causative agents of bacterial meningitis
a) Young to middle age dogs
b) Boxers, Beagles, Bernese mountain dogs
c) Fever, depression, neck pain
d) Non-degenerative neutrophils
e) Degenerative neutrophils
f) Staphylococcus species, E. coli, Pasteurella species
Respiratory tract wash
a) tracheal wash
b) bronchoalveolar lavage
c) tubes used to collect samples
a) TW samples trachea (URT disease)
b) BAL samples lower airways and alveeoli (LRT disease)
c) EDTA tube for cytology, plain tube for culture
Respiratory tract washes
Normal BAL/TW findings
a) Cell type predominant
b) Neutrophil presence
c) Eosinophil presence (dogs and cats)
a) Alveolar macrophages (70-80%)
b) Low numbers (< 10%)
c) Rare in dogs (< 5%), < 25% in cats
Respiratory tract washes
Neutrophilic inflammation BAL/TW findings
a) Changes to neutrophils
b) Causes (4)
a)
- Increased number (> 10%)
- degenerative changes to neutrophils would suggest bacterial infection
b)
- bacterial infection
- other infectious agents (viral, protozoal)
- foreign body
- neoplasia
Respiratory tract washes
Eosinophilic inflammation BAL/TW findings
a) Cell number changes
b) Causes (5)
a)
- Increased eosinophils
- may see mast cells, plasma cells, lymphocytes
b)
- parasites
- hypersensitivity/allergic
- eosinophilic bronchopneumopathy
- bacteria/fungal
- neoplasia
Respiratory tract washes
Equine BAL
a) Severe equine asthma
b) Mild to moderate equine asthma
c) Exercise induced pulmonary haemorrhage
a) Common in older stabled horses. Neutrophilic BAL
b) Affects horses of any age. Increased neutrophils, lymphocytes, eosinophils and mast cells on BAL
c) Common cause of poor performance. > 50% Haemosiderophages in BAL
Infectious disease diagnosis
How to test for bacteria infections, including considerations for aerobic and anaerobic cultures
- Visualisation often possible
- Culture is gold standard, allows antimicrobial susceptibility testing
- Aerobic: tissue or fluid culture, use charcoal transport medium
- Anaerobic: tissue or fluid culture, avoid refrigeration as will kill bacteria
Infectious disease diagnosis
How to test for FeLV and FIV
- SNAP test (FIV serology, FeLV antigen detection in blood)
- PCR using bone marrow used to confirm infection is positive on SNAP test
Infectious disease diagnosis
How to test for FIP
- PCR of effusions/tissue
- Immunohistochemistry on biopsy or histopathology (detect coronavirus within macrophages)
Infectious disease diagnosis
How to test for Feline herpes and Feline Calcivirus
- PCR on oral/conjunctival swab
- Virus isolation from oral/conjunctival swab
Infectious disease diagnosis
How to test for Chlamydophila felia
- PCR on conjunctival swab
- Visualisation to look for inclusions in ocular squamous epithelial cells
Infectious disease diagnosis
How to test for canine parvovirus
- Parvo FASTest on faeces sample
- PCR on faeces
Infectious disease diagnosis
How to test for canine leptospirosis
- PCR on blood and urine
- Serology (although confounded by vaccination)
Infectious disease diagnosis
How to test for canine distemper virus
- PCR on CSF or blood
- Serology (vaccination can confound)
Infectious didsease diagnosis
How to test for Angiostrongylus vasorum
- SNAP test on faeces
- PCR on bronchoalveolar lavage or blood
Infectious disease diagnosis
How to test for Giardia infection
- Giardia SNAP on faeces
- Visualisation on cytology
Infectious disease diagnosis
How to test for Mycobacteria species
- PCR on tissue sample
- Visualisation on cytology/histopathology with Ziehl-Neelson stain
