Lab Information I forget Flashcards
Define MCV and how is it calculated
Mean corpuscular volume
The average volume of a red blood cell expressed in femtolitres
Haematocrit x10/RBC
What is MCH and how is it calculated
Mean corpuscular haemoglobin
The average weight of haemoglobin per red blood cells
Hb/RBC
What is MCHC and how is it calculated?
Mean corpuscular haemoglobin concentration
The average Hb in a given volume of blood in grams/litre
What is MCHC and how is it calculated?
Mean corpuscular haemoglobin concentration
The average Hb in a given volume of blood in grams/litre
Hb x 100/Hct%
How do we measure haemoglobin
Drabkins method/cyanmethaemoglobin method -> red colour spectrophotometry
Define haematocrit
A measurement of the proportion of blood that is made up of red cells
What causes microcytic and hypochromic rbcs
Iron deficiency
Thalassaemia
What is the Wright Stain
A polychromatic stain consisting of buffered solutions of methylene blue and eosin
Type of Romanowsky stain
What is a howell jolly body
DNA remnant
What is basophilic stiplling
Denatured RNA
What is basophilic stiplling
Denatured RNA
What are siderotic granules
Iron
What are heinz bodies
Oxidised denatured Hb
What is Turks solution
Stain used when counting WBC using a haemocytometer
Stain contains gentian violet and 6% acetic acid, gentian blue stains wbcs while acetic acid lysis rbcs
What is the romanowksy stain
A series of blue/red stains where the blue binds to acidic substances and the red binds to neutral or basic substances
What anaemias will increase reticulocytes
(5)
Thalassaemia
Pernicious anaemia after treatment
Iron deficiency anaemia after treatment
Haemolytic anaemias -> spherocytosis
Sideroblastic anaemia
What conditions will decrease reticulocyte counts
Aplastic anaemia (no new cells)
Untreated pernicious anaemia
Megaloblastic anaemia
Untreated iron deficiency anaemia
Anaemia of chronic infection
Chemotherapy
How do we investigate hereditary persistance of HbF
The Kleihaeuer Betke test
acid elutes HbA
HbF stains dark pink
What primary techniques are used to investigate haemoglobinopathies
HPLC
Isolectric focusing IEF
Hb electrophoresis
What secondary techniques are used to investigate Haemoglobinopathies
Hb electrophoresis
HPLC
Sickle solubility test
What is the principle behind HPLC
Different variants have different retention times
Hb is absorbed into column and eluted by means of a gradient of increasing ionic strength
Exchange column contains small spheres of silica which are modified to be weakly cationic
An anticoagulated specimen is lysed and diluted in buffer and injected into column
Hb is absorbed into column and eluted by means of a gradient of increasing ionic strength
Eluate passes through a photometer which measures changes in absorbance
What is the principle behind Hb electrophoresis
HBE utilises the charged properties of normal Hb and its variants to replicate characteristic mobility patterns on both alkaline and acidic gels
What is the principle of the sickle solubility test
HbS is insoluble in the deoxygenated state in a high molarity phosphate buffer (sodium hydrosulfite)
The crystals that form refract light and cause the solution to be turbid, can’t see through
Thin blood film
Stained with Giemsa stain at pH 7.2
Used to determine % parasitaemia count
Used to determine species of parasite
Used to note the different stages of development seen
Thick blood film
Stained with fields stain
Used to detect the presence of the parasite
Useful in low grade parasitaemias
Sensitivity
A tests ability to determine the patient cases correctly
Sensitivity
A tests ability to determine the patient cases correctly
True positive/(true positive + false negative)
Specificity
A test’s ability to determine the healthy cases correctly
True negative/(true negative + false positive)
Five main stages to the development of a granulocyte
Myeloblast
Pro-myelocyte
myelocyte
Meta-myelocyte
Granulocyte
Precision
How well a series of measurements agree with each other
It is the closeness of agreement between independent test results obtained under stipulated conditions
Accuracy
How well a measurement agrees with an accepted value
It is the closeness of the agreement between the result of a measurement and a true value of the measurement
Deviation index
is a statistical tool used to assess the accuracy and precision of laboratory test results. It helps evaluate how closely the measured values obtained in the laboratory align with the expected or target values.
1 or lower is really goos
1-2 is satisfactory
2-3 is borderline
3 may indicate a problem
Coefficient of varation
The coefficient of variation (CV) is a statistical measure used to assess the relative variability or dispersion of a dataset in relation to its mean. It is expressed as a percentage and provides a standardized measure of dispersion that allows for comparison between datasets with different means
A measure of precision
CV = (Standard Deviation / Mean) * 100
below 10% indicates results are near the mean and are precise
Mean
Average of the values
Standard deviation
a measure of the dispersion or spread of values in a dataset. It quantifies how much the individual data points deviate from the mean
A higher standard deviation indicates a greater spread or variability of values in the dataset
What four tests are carried out for iron deficiency anaemia
Serum iron
Transferrin (TIBC)
% transferrin saturation
Serum ferritin
How is %transferrin determined
Serum iron/TIBC x1000
How is %transferrin determined
Serum iron/TIBC x100
What are the clinical findings of iron deficiency anaemia?
Decreased:
- Haemoglobin
- MCV
- MCH
- Reticulocytes
- Ferritin
- serum iron
- 15%> transferrin %
Hypochromic, microcytic rbcs
Clinical findings of Thalassaemia
Reduced
- Haemoglobin
- MCV
- MCH
- haptoglobin
Increased
- Reticulocytes
- Lactate dehydrogenase
- Bilirubin
Hypochromic
Microcytic
Target cells
Anisopoikilocytosis
Pappenheimer bodies
Basophilic stipppling
Inclusion bodies (HbH only)
What tests should be carried out for B thalassaemia
HPLC -> low HbA, high HbF and HbA2
Gel electrophoresis
Family studies
DNA analysis
What tests should be carried out for a Thalassaemia
H prep
HPLC -> HbH peak and Hb Barts
Gel electrophoresis
Family studies
DNA analysis
How is a H prep carried out
Incubation with brilliant Cresyl blue
HbH will precipitate
Results in appearance of multiple discrete inclusions - golf ball apoearance
Clinical findings of megaloblastic anaemia
Increased:
- MCV
- MCH
- Lactate dehydrogenase and bilirubin
MCHC (normal or low)
Reduced:
- WCC
- platelets
- haptoglobin
- reticulocytes
Oval macrocytes
Hypersegmented neutrophils
Stages of granulocyte
Haematopoietic stem cell follows the myeloid pathway -> develops into a CFU-GEMM
CFU-GEMM into CF-GM
Depending on stimulus GF-GM will develop into a different granulocyte:
- G-CSF = neutrophil
- IL-5 = eosinophil
- SCF = basophil (can become mast cells in tissues)
Neut CFU -> myeloblast, promyeloblast, myeloblast, myelocyte, metamyelocyte, mature neutrophil
Grow factor inhibits apoptosis and promotes differentiation
Clinical findings of ALL
High lymphoblasts greater than 20%
Low red cell count
Low haemoglobin
Low platelet count
Hypercellularity in bone marrow
Philadelphia chromosome - BCR-ABL1
Clinical findings of AML
Varying degrees of myeloblast increase
Auer rods
Clinical findings of CLL
Hair cells
Smudge cells
Increased reticulocytes
Haemoglobin decreased
Neutropenia
B Cells expressing CD19, CD5, CD23, CD20
Clinical findings of CML
Red blood cell count down
Little to no platelets
White blood cell count up
Blast cells
Clinical findings of HS
Spherocytes
Anaemia + splenomegaly + jaundice depending on severity
Increased:
- MCHC
- reticulocytes (not always)(recovery phase)
- bilirubin
Normal or reduced MCV
What do we need to rule out for HS
EMA
Autoantibodies
Autoimmune haemolytic anaemia
Irregular maternal IgG antibodies
What tests are carried out for HS
EMA flow cytometry
SDS-page
osmotic fragility test
Clinical findings for G6PD
Decreased:
- haemoglobin
- MCV
- haptoglobin
Increased
- NRBCs
- reticulocytes
- LDH
- bilirubin
MCH normal
Bite cells
Heinz bodies
What tests are carried out for G6PD
Heinz body stains
MetHb reduction
Fluorescence spot screening
DNA analysis
Explain oxygen dissociation curve
The oxygen dissociation curve is a curve that plots the proportion of Hb in its oxygen saturated form on the vertical axis against the prevailing oxygen tension on the horizontal axis. It’s important for understanding how our blood carries and releases oxygen. It relates oxygen saturation (SO2) and partial pressure of oxygen in the blood (PO2). It is determined by haemoglobin affinity for oxygen i.e. how readily haemoglobin acquires and releases oxygen molecules into the fluid that surrounds it
