Haematology & Anemia Flashcards
List the types of laboratory blood tests that can be used
Haemocytometer (RBC count)
Microhematocrit
Microscopic examination of blood smears
Automated analysers
-Coulter principle
-Laser cell counters
-Quantitative buffy coat analysis
List the types of laboratory blood tests that can be used
Haemocytometer (RBC count)
Microhematocrit
Microscopic examination of blood smears
Automated analysers
-Coulter principle
-Laser cell counters
-Quantitative buffy coat analysis
Describe the blood test microhaematocrit
Measures the ratio of the volume occupied by packed red blood cells to the volume of the whole blood
This equals the Packed cell volume or PCV
Rapid & cheap in house test that gives large amount of information
Other than PCV what other information can microhaematocrit tell you
indications to dehydrations, jaundice, haemolysis, any artefacts, lipaemia, leukocytosis or thrombocytosis’
Describe the use of automated cell counters
Dependent Coulter principle (electrical technique): to enumerate and identify blood cell populations
- A stream of cells passes through an aperture between two chambers, across which there is an electrical current.
- Passing cells disrupt the electrical flow, causing a pulse:
Amplitude is proportional to cell volume
Pulse frequency provides information of cell number
Absorbance: to measure haemoglobin
Outline the production of size destitution plots by use of cell counters
Histograms plotting the cell number against cell size.
Measured values
-Red blood cells - absolute number per litre
-Mean corpuscular volume (MCV) - the average volume of the red cells (fl)
-Platelets - absolute number per litre
-White blood cell counts - absolute number per litre
-Haemoglobin - The amount of haemoglobin in the blood (g/l)
Explain the derivation and meaning of mean cell volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC)
Explain the derivation and meaning of packed cell volume (PCV) and outline the calculation
Hematocrit (Hct) = packed cell volume (PCV)
This is the fraction of whole blood volume that consists of red blood cells.
Calculated Hct/PCV:
Hct/PCV = MCV x RBC count/100
Explain the derivation and meaning of mean corpuscular hemoglobin (MCH) and outline the calculation
The average amount of hemoglobin per red blood cell, in picograms.
MCH pg = Hb x10/RBC count
Explain the derivation and meaning of corpuscular hemoglobin concentration (MCHC) and outline the calculation
The average concentration of hemoglobin in the cells relative to size/volume of cell.
MCHC g/dl = Hb x100/Hct
Discuss the limitation pf automated systems
They will not give reliable differential white cell counts (especially if there are abnormalities).
Even laser based in-clinic analysers and even combined laser/impedance analysers are also not perfectly reliable.
Occasionally small RBCs will be undercounted and counted as platelets.
Large platelets may get counted as red cells.
Can’t ID RBC morphology, WBC morphology or blood parasites
List some common problems with blood samples
Correct tube selection (correct anti-coagulant for the test requested)
Clotting
Haemolysis
Appropriate tube fill
Lipaemia
Labelling (Species!)
Discuss the use of the skill microscopic examination of blood smears and the benefit of microscopic examination
Differential leukocyte counts
diversity of leukocyte patterns in cats & dogs
Erythrocyte and leukocyte morphology
Presence of any abnormal cells & parasites
Platelet counts – manual estimate to confirm results from automatic analysis
Send with EDTA sample for blood analysis
To distinguish the effect of “sample aging” during transport and genuine diagnostic findings
Quick & low cost diagnostic tool which is often used by charities such as PDSA
Explain use of erythrocyte sedimentation rate blood test
Erythrocyte sedimentation rate
An increase in ESR is a non-specific change in many diseases
The sedimentation rate is probably due to changes in the plasma that encourage agglutination
Which lead to larger aggregates that sediment more rapidly
Describe the use of erythrocyte sedimentation rate in different species
Horses –ESR too high in healthy animals to notice increase due to disease
Ruminants – no increase due to disease
Dogs 5-10 mm/h
Pigs 2-14 mm/h
-during disease these levels can rise more than 10fold
