Lecture 6 Flashcards
What are the turn around times for urgent/non-urgent/GP labs?
Urgent: 1 hour (A and E)
Non-urgent: 4 hours (ward patients)
GP: 24 hours
What do you class as abnormal results?
Results outside the normal range
-not always the case as normal range only includes 95% of the population
Significant fall in value
What are some normal range changes due to?
Age
Sex
Ethnicity
Co-morbidities
Whatdo you do if the FBC was unexpected?
Repeat test (as could be due to sampling/storage/lab errors)
What errors can occur in pathology results?
- specimen mix up
- wrong bottle
- poor technique
- pooling samples
- speciment delayed/not delivered
- wrong delivery method
- incorrect clinical details
- wrong test requested
- technical error
- right result applied to wrong patient
- results not reviewed
- reflex tests not carried out
What is a FBC?
Automated panel of tests to determine any haematological abnormalities
What is spectrophometry used to analyse in a FBC?
Amount of Hb
- amount of light absorbed by sample proportional to amount of absorbent compound in it
- hypotonic solution to lyse cells
- use calibration to determine sample concentration
What must FBC samples be placed in a tube with?
EDTA (ethylenediaminetetraacetic acid) and mixed
-EDTA chelates Ca2+ ions acting as an anticoagulant, as a clotted sample would be useless
What is important when taking a blood sample for UE analysis (urea/electrolyte)?
Never pour blood from an FBC tube into a UE tube.
-the K+ salt of EDTA would give a very high K+ reading
What is a WBC and how do you obtain it?
White blood cell count
Automated cell counting
-interruption of a beam of light/electrical current as a line of single cells flowing through a narrow tube
-after the RBC’s have been lysed
What is a RBC and how do you obtain it?
Red blood cell count
Measured the same as WBC count, except that the RBC’s aren’t lysed
(white cells will be counted but they are so low in number compared, they don’t affect reading)
What is haematocrit (HCT)?
Fraction of whole blood volume which consists of RBC’s
How is HCT measured?
Previously measured by centrifuging blood sample and comparing height of red cell fraction with height of sampleto give the packed cell volume (PCV)
Now
-multiplying average red cell size (MCV) by number of red cells per litre
What is the MCV and what is it useful for?
Mean cell volume
- average volume of red cells measured in femtolitres measured by analysers (amount of light/current impeded is proportional to size of cell)
- useful in detecting a microcytic/macrocytic anaemia
What is the MCH and how is it determined?
Mean cell haemoglobin
- average amount of Hb protein in an individual RBC
- calculated by dividing the Hb concentration in a given volume of blood by number of red cells in that volume
How is the platelet count measured?
Same as red and white cells.
Platelets are much smaller so can easily be distinguished by the analyser as they produce a much smaller signal
How is the reticulocyte count measured?
Stain/ fluorescent dye which bind to ribosomal RNA (rRNA is not present in mature RBC’s)
What is a differential white blood cell count?
Blood analysers can recognise the 5 normal types of white cells (neutrophils, lymphocytes, monocytes, eosinophils, basophils)
-if abnormal cells are present it is best to count them manually on blood film
What is a blood film?
Peripheral blood smear to inspect blood cell morphology.
Monolayer of cells which can easily be viewed under a microscope
-sample is air dried and fixed in methanol before staining to distinguish different cell types
What are blood films usually used to assess?
- Causes of low RBC/WBC/platelets
- check for blood parasites (malaria)
- check for abnormalities (sickle cell, spherocytosis)
What is an increase/decrease in RBC’s called?
Increase: polycythaemia/erythrocytosis
Decrease: anaemia
What is an increase/decrease in WBC’s called?
Increase: leucocytosis
Decrease: leucopenia
What is an increase/decrease in lymphocytes called?
Increase: lymphocytosis
Decrease: lymphocytopenia
What is an increase/decrease in monocytes called?
Increase: monocytosis
Decrease: monocytopenia
What is an increase/decrease in neutrophils called?
Increase: Neutrophilia
Decrease: Neutropenia
What is an increase/decrease in eosinophils called?
Increase: Eosinophilia
Decrease: eosinopenia
What is an increase/decrease in basophils called?
Increase: basophilia
Decrease: basopenia
What is an increase/decrease in platelets called?
Increase: thrombocytosis/thrombocythaemia
Decrease: thrombocytopenia
What is an increase/decrease in all blood cell types called?
Increase: panmyelosis
Decrease: pancytopenia
What is agglutination?
RBC’s forming irregular clumps
What is a schistocyte?
RBC fragment
What is a target cell?
RBC where Hb is concentrated at periphery and a dot in the centre
What is a spherocyte?
RBC is a spherical shape (lacks central pallor)
What is an ovalocyte?
RBC in an oval shape
What is an elliptocyte?
RBC in an elliptical shape
Whatis hypochromia?
Presence of abnormally pale cells
What is aniscocytosis?
Greater than normal variation in cell size
What is poikilocytosis?
Greater than normal variation in cell shape
What is a stomatocyte?
A RBC with a slit like stoma (central white part)
What is an echinocyte?
Crenated cell: RBC with large number of irregular spurs
What is an acanthocyte?
Spur cell: RBC with small number of irregular spurs
