Interpreting Full Blood Count Flashcards
What can a normal range change with ?
- age
- sex
- ethnicity
- co morbidities
What are the 4 types of errors that can occur in pathology results?
1) specimen collection
2) delivery of specimen to lab
3( specimen analysis and result reporting
4) responsive action
What are ways errors can occur in specimen collection ?
1) wrong bottle
2) pooling samples
3) poor technique
4) specimen mix up
What are ways errors can occur in delivery of specimen to lab ?
1) specimen delayed or not even delivered
2) wrong delivery method
What are ways errors can occur during specimen analysis and result reporting ?
1) specimen mixing up
2) incorrect clinical details
3) wrong test requested
4) technical error
What are ways errors can occur during the response action ?
- reflex tests not carried out
- result not reviewed
- right result applied to wrong patient
What do you do as a clinical if you get an abnormal or unexpected result ?
Repeat
What is a full blood count
Term used to refer to a panel of tests routinely performed on a blood sample in order to determine whether or not there are any haematological abnormalities present.
Where must blood samples for full blood count be placed in ?
- they must be placed in a tube containing EDTA and mixed.
- EDTA chelates Ca2+ and therefore acts as an anticoagulant. Without the chelating agent , the blood sample would clog and be useless for analysis.
What are three full blood count analyser techniques ?
1) spectrophotometrey
2) flow cytometry
3) flow cytometry differential
Outline the method of spectrophotometry
- the amount of light absorbed by the sample is proportional to amount of absorbant compound within it.
- this is used to measure HB
- hypotonic solution used to lyse cells
- use light of appropriate wavelength
- use calibration curve to determine sample conc
Outline method of flow cytometry
- hydrodynamic focussing of a single file line of cells which pass through a light beam
- the more scatter there is , the bigger the size of the cell
What is flow cytometry differential analyser technique
- forward scatter indicates size
- but side scatter indicates intracellular complexity or mono/polymorphonuclear
Define packed cell volume ( PCV) / haematocrit
Proportion of blood that is made up of RBC
What is the packed cell volume / haematocrit used to identify?
- anaemia
- but more often polycythemia ( slow growing blood cancer in which the body makes too much red blood cells )
Define haemoglobin concentration
Amount of hb in blood (g/L)
What is the reference range of HB in adult men and adult women and children and newborns ?
NEWBORNS- 150g/L
- CHILDREN ; 110g/L
- WOMEN : 115g/L
- MEN : 135 g / L
What could increase the HB concentration in the blood ?
,
Would measuring HB concentration in vitro affect the actual value of HB ?
yes , the value would decrease because red blood cells lyse in tube
Why would a clotted sample reduce hb?
Because RBC would be recruited to that clot
Define red cell count
Number of red blood cells in a given volume of blood
What is red blood cell count used to indicate ?
1) anaemia ( eg microcytic anaemia which is Chaucer. H reduced iron or increased thalassemia trait)
2) erythrocytosis ( an increase in red blood cells) - if detected more likely to be polycythaemia
What is the most important parameter used to screen the cause of anaemia ?
Mean cell volume
How is mean cell volume measured of RBC?
Measured using the amount of light scattered as they pass in a single file last a laser
What are a few diseases that could be associated with low mean cell volume ?
1) iron deficiency anaemia
2) thalassaemia
3( anaemia of chronic diseases
4) lead poisoning
What are a few diseases that are associated with high mean cell volume ?
1) megablastic anaemia ( B12, folate)
- liver diseases
- alcohol , smoking
- drugs especially HIV drugs
Define mean cell haemoglobin
Average measure of the amount of HB in each RBC
What is mean cell HB used in assement for ?
Anaemia
- if there is a reduction in mean cell haemoglobin it is often because of iron deficiency
- it is normal or increased in macrocytic anaemias
Red cell distribution width
Variation in size of RBC
Is red cell distribution width increases what is this an indication of ?
- increased in iron deficiency
- after transfusion , there will be an increase
Recticulocytes count
Measurement of the number of young erythrocytes
- they are identified using size and RNA content
If recticulocytes count is increased , what does this indicate ?
1) haemolytic anaemia
2) recent blood loss
3( recovery from bone marrow suppression
4) response to EPO
If recticolcyte count is reduced , what does this indicate ?
Bone marrow failure
When will a blood film be requested ?
When there is a significant result outside of the normal range
- significant change within the normal range
Outline the process to create a blood film
1) small drop of blood spread onto a glass slide ( one cell thick layer H
2) fixed with methanol
3) stained to enable visualisation under microscope
Define microcytic
Small red blood cells
Define macrocytic
Large red blood cells
Define hypochromic
Pale , less HB
Define hyperchromic
Dense , more HB in given volume
Spherocytosis
Spherical RBC
Elliptocytosis
Elliptical RBC
Sickle cell
Crescent or sickle shaped cells
Anisocytosis
Variation in size
Dimorphism
Two distinct population sof red cells
Target cells
RBC with dark area in the middle of the area of central pallor
Polychromatic
Many colours
Schistiocytes
Red cell fragments
