Interpreting FBC Flashcards
Reasons for errors in lab results
Specimen collection: mix up, wrong blood in tube, wrong bottle, pooling (mixed two samples), poor technique
Delivery: Specimen delayed/not delivered, wrong delivery method
Specimen analysis: Specimen mix up (booking in, incorrect clinical details, wrong test requested, test variability, technical error
Responsive action: Results not reviewed, reflex tests not carried out, right result to wrong patient
What must a sample be for FBC analysis?
k-EDTA anticoagulated
Chelated calcium ions
(stops blood coagulation)
FBC analyser
Closed system
Easy maintenance
Copes with high numbers of samples
Spectrophotometry
Amount of light absorbed by sample (proportional to amount of absorbent compound within it)
Need hypotonic solution to lyse cells
Flow cytometry
Single file line of cells
Counts as passes through light beam
(more scatter = big cell)
What is packed cell volume/haematocrit?
Proportion of blood that is made up of RBC (assess polycythaemia)
Centrifuged to visualise
Layers of centrifuged blood
Plasma - water, proteins, nutrients, hormones
Buffy coat - white cells, platelets
Haematocrit - RBC
Hb
Concentration of haemoglobin in blood (Hb mass per plasma volume)
Acute bleed/dehydration effects results
RCC - red cell count
Number of RBC in given volume of blood (assess anaemia/erythrocytosis)
Red cell count high and low
Low - iron deficiency anaemia
High - thalassaemia trait, true polycythaemia (in polycythaemia caused by reduced plasma RCC will not be raised)
MCV (mean cell volume)
Determines cause of anaemia
Increased MCV =
Megaloblastic anaemia (B12/Folate) Liver disease Alcohol Haemolytic anaemia (reticulocytes = large) Hypothyroidism Drugs (HIV) Myeloma
Decreased MCV =
Iron deficiency
Thalassaemia
Anaemia of chronic disease
(TIA)
RDW - red cell distribution width
Shows variation in size of RBC
If increased - anisocytosis (different sizes)
what can RDW be used for in regards to anaemia?
Assess timeline/cause
Increased in recent anaemia development and haemolysis (reticulocytes)
Normal in thalassaemia
MCH - mean cell haemoglobin
Measure of haemoglobin in each RBC
Assess anaemia
MCH results
Reduced in iron deficiency, thalassaemia and haemoglobinopathy
Raised in macrocytic anaemia
Normal in mixed deficiency
Reticulocyte count use
Measures number of young blood cells (size and RNA content)
When will reticulocytes be raised?
Haemolytic anaemia Recent blood loss Response to iron, folate, B12 replacements EPO stimulation Recovery from bone marrow suppression
When will reticulocytes be reduced?
Haematinic deficiency (eg iron, folate etc)
Bone marrow failure
Parvovirus (targets precursors)
Hypochromic vs hyperchromic
Hypo = low MCH (pale, less Hb)
Hyper = high MCH (dense, more Hb)
Polychromatic meaning
Reticulocytes present
Poikilocytosis
Abnormally shaped RBC
Anisocytosis
Variation in size of RBC
