Lecture 2: Haematology Techniques and Parameters Flashcards
(15 cards)
What are the 3 patient identification checkpoints before blood collection?
Name, DOB, and hospital number (or address).
Why is order of draw critical during venesection?
Prevents cross-contamination (e.g., EDTA → falsely ↑ K⁺/↓ Ca²⁺ if drawn before coagulation tubes).
What tube is used for FBC and why?
K₂EDTA (purple top) – prevents clotting by chelating calcium.
Difference between serum and plasma?
Serum: Clotted blood (no fibrinogen; yellow/red top).
Plasma: Anticoagulated blood (blue/grey top; retains clotting factors).
Which tube is used for glucose testing if delayed processing?
Fluoride oxalate (grey top) – inhibits glycolysis.
What happens if a sodium citrate (blue top) tube is underfilled?
Excess anticoagulant dilutes analytes → falsely low results (e.g., PT/APTT).
Causes of haemolysed samples?
Rough handling, fine needle use, or delayed separation → falsely ↑ K⁺, LDH.
How does lipaemia affect lab results?
Interferes with colorimetric assays (e.g., falsely ↓ Na⁺ via indirect ISE).
What does icteric serum indicate?
High bilirubin (>300 µmol/L) → interferes with Jaffe creatinine assay (falsely low).
What does MCV measure?
Mean Cell Volume (RBC size; normal = 80–100 fL).
How is haematocrit (Hct) calculated?
Hct = (MCV × RBC count) / 1000 (e.g., MCV=90fL, RBC=5.0×10¹²/L → Hct=45%).
What stain is used for manual blood films?
Modified Wright’s stain (eosin = red/orange; methylene blue = blue/violet).
Why is ESR higher in anemia?
Fewer RBCs → faster rouleaux formation → ↑ sedimentation rate.
What does plasma viscosity measure, and why is it unaffected by anemia?
Reflects fibrinogen/large proteins; only plasma is tested (no RBC dependence).
Which is more specific for inflammation: ESR or plasma viscosity?
Plasma viscosity (less affected by RBC abnormalities).
