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Haematology and Transfusion > Techniques & Parameters > Flashcards

Techniques & Parameters Flashcards

1
Q

What Constitutes Blood?

A
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2
Q

What is the difference between serum and plasma?

A
  • Serum is the liquid part of blood AFTER coagulation, lacking clotting factors such as fibrinogen
  • Plasma is the liquid, cell free part of blood that has been treated with ANTICOAGULANTS
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3
Q

Pre-analytical factors

A
  • Correct details on form / samples - are from the correct patient
  • Correct patient preparation
  • Recorded time of collection
  • Collected into correct tube
  • Stored correctly
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4
Q

Pre-analytical factors:

GP’s/Clinicians

A
  • What is the appropriate test?
  • Any special patient preparation? –
  • Need to inform patient prior to blood test
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5
Q

Pre-analytical factors:

Patients

A
  • Do they need to fast?
  • Do they need to stop medication?
  • Do they need time blood test to their last medication dose?
  • Do they need to go on a set day within a cycle?
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6
Q

Pre-analytical factors:

Phlebotomists

A
  • Any special patient preparation?
  • Does the sample need protecting from light?
  • Does the sample need to be sent on ice / to lab ASAP?
  • What is the correct sample tube?
  • What order do tubes need to be taken in (and mixing)?
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7
Q

PATIENT IDENTIFICATION

3 check points of identification:

A
  • Name
  • DOB
  • hospital number

Address

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8
Q

YOU must know…..

A
  • Your local procedures to employ when requirements are not met !!
  • Sample rejection criteria
  • What to do if samples are not received correctly
  • How are rejected samples reported?
  • Why it is important that they are rejected
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9
Q

VENESECTION

A
  • Sitting and lying down?
  • Tourniquet use
  • Correct sample tube
  • Order of draw
  • Site of draw
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10
Q

What happens when you cut yourself?

A
  1. Blood vessels constrict
  2. Platelet plug forms (requires calcium)
  3. Clotting cascade activated (requires calcium)
  4. CLOT: platelets + fibrin
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11
Q

Blood samples- whole blood

A
  • Need to keep it free flowing
  • Need to prevent clotting
  • Use K+ EDTA as an anticoagulant
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12
Q

Blood samples- serum

A
  • Yellow top – clot activator and gel (red no gel)
  • Cells separated through centrifugation – serum above the gel
  • Gel is not a complete barrier

U&E’s, LFT, lipids, cholesterol, thyroid function tests, bone profile

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13
Q

Sodium citrate (blue) is used for

A

coagulation testing

(plasma)

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14
Q

Flouride oxalate (grey) used for

A

glucose and lactate

(plasma)

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15
Q

Is the the order of draw important?

A
  • Extremely Important
  • Mixing is essential
  • Must avoid contamination
  • Need to know the tubes required for requested tests AND what order to take them in
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16
Q

What is the order of draw?

A
  • Blood Culture Tubes or Vials.
  • Coagulation Tubes (Blue-Top Tubes)
  • Serum Tubes without Clot Activator or Gel (Red-Top tubes)
  • Serum Tubes with Clot Activator or Gel (Gold or Tiger Top Tubes)
  • Heparin Tubes (Green-Top Tubes)
  • EDTA Tubes (Lavender-Top Tubes)
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17
Q

What are common mistakes with the order of draw?

A

Common mistake is to draw K+EDTA or Na citrate tubes first – What effects would this have?

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18
Q

Effects of EDTA contamination

A
  • K-EDTA - anti-coagulant (purple top tube)
  • Contains K (potassium)
  • Contains chelating (binds calcium) agent EDTA
  • Analytes affected
  • Increase ↑ K
  • Decreases ↓ Ca / ALKP
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19
Q

Effects of Na Citrate contamination

A
  • Contains Na
  • Liquid anticoag – 0.5ml
  • Increases Na ↑ (160 mmol/L)
  • Dilution effect on other analytes
  • Results look like a very sick patient
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20
Q

Effects of Fl Oxalate Contamination

A
  • Na F and K-oxalate
  • Powdered - if not mixed properly – fibrin clots
  • Contains Na ↑ (220 mmol/L)
  • Contains K ↑ (45 mmol/L)
  • Contains Ca ↓ (0.95 mmo/L)
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21
Q

Name some Blood tests and the corresponding anticoagulants

A
  • Full blood count (FBC) - blood- sodium or potassium salt EDTA
  • Coagulation tests - plasma- sodium citrate
  • Erythrocyte Sedimentation Rate (ESR)- blood- prevented by sodium citrate
  • Cytogenetic analysis- Heparin
22
Q

What transport considerations need to be made?

A
  • Priority sample
  • Urgent processing
  • Temperature
  • Time
  • Transport on ice?
  • Transport in heat block?
23
Q

Contamination-effects of storage

Glucose:

A
  • Delay in separation
  • Glycolysis - Mis-diagnosis of hypoglycaemia
  • Glucose must be collected in fl.ox tubes if sample is going to take longer than 4 hrs to separate off cells
24
Q

Contamination-effects of storage

Other analytes

A

Leakage from RBC’s = Na /K shift

Intracellular ↔ extracellular components

  • Serum on cells > 6 hrs - K ↑
  • Serum on cells > 24 hrs - PO4 ↑ LDH↑ Fe ↑ folate ↑ and red cell enzymes
  • On cells >3 days - also affects Na+↓
25
Q

Why must you be aware of what sample tube contamination looks like?

A
  • BMS staff are required to technically validate results
  • Wrong tube or delays to analysis can affect some analytes
  • You will need to be able to spot this and know what to do
26
Q

Describe normal serum

A
  • Straw coloured serum
  • Bilirubin <17umol/L
  • Approx equal volume of serum = cells
27
Q

Less cells / more serum =

A

anaemia

28
Q

More cells /less serum =

A

polycthaemia

29
Q

Describe a haemolysed sample

A
  • Lysis of red blood cells (Haemolysis)
  • Poor blood collection technique
  • Shaken / fine bore needle into vacuum tubes
  • Release of K and other red cell constituents (i.e. enzymes)
30
Q

Describe a lipaemic sample

A
  • Also known as lipaemia
  • Abnormally high concentration of lipids in the blood
  • Taken too soon post prandial (after food)
  • Lipid layer causes dilution effect with indirect ISE – falsely low Na
  • Interference with some colorimetric tests – unable to process
31
Q

Describe an icteric sample

A
  • Serum is dark yellow, brown or greenish
  • Bilirubin is grossly elevated > 300umol/l
  • Interferences with Creatinine Jaffe method – falsely low result
32
Q

Describe a lipaemic and haemolysed samples

A

Strawberry milkshake!

Many analytes are not reported due to interferences i.e. Na, K, bili and enzymes

33
Q

What could cause a green sample?

A

Drug interference

  • Methylene blue test
  • Interferences with assays
34
Q

Name some analytical factors

A
  • Maintainance procedures – daily / weekly / monthly / non scheduled
  • Reagents in date / stored correctly/ made up correctly
  • Check Calibration failures – correct lot no, made up correctly, correct std value installed
  • Has the assay passed quality assurance checks?
  • Have any IQC failures been investigated?
  • Fliers on results due to imprecision or falsely low results due to clotted serum samples – MUST be investigated
35
Q

Hb level via spectrometry

A

Used to provide the Haemoglobin result- to a WHO standard

36
Q

Full blood count via flow cytometry

A
37
Q

FBC can also be measured by

A

Impedance

38
Q

Siemens 21:20 analyser

A
  1. Analyser draws samples into machine to mix
  2. Clot filter
  3. Shear valve
39
Q

Results from an analyser

A
  • Absorption RBS=HB
  • Absorption Platelet= granulation
  • Dark blue- mononucleo cells- lymphocytes
  • Purple- neutrophils and eosinophils
40
Q

Analysers produce red cell indices

A
  • Haematocrit (hct) = Proportion of whole blood taken up by red blood cells- expressed as 0.42L/L or 42%
  • Other red cell indices:
  • MCV= Mean cell volume- 95 fL
  • MCH= Mean cell HB -29.5 pg
  • MCHC= Mean concentration of HB-330 g/L

Hct= (MCVXRBCC)/(1000)

41
Q

White cell differential

A
  • Analyser uses Cytochemistry
  • Stains intracellular myeloperoxidase content of cell

Purple= neutrophils

Blue= lymphocytes

42
Q

What is light microscopy used for?

What dyes are used?

A
  • Used to clarify results from analysers
  • Further analysis of size, maturity & shape
  • Kohler illumination
  • Drop of blood smeared on slide is fixed

Modified Wrights stain (based on Romanowsky)

1.Methylene Blue

basic dye

Stains acidic parts of cell blue-violet colour eg. Nucleus, granules of basophils

  1. Eosin

Acidic dye

Stains Hb, eosinophil granules red/orange

43
Q

Blood film confirms analyser results

A
  1. Assess red cell size - nice uniform size, circular paler centre of pallor
  2. Normal RBC comparable to a small lymphocyte
  3. Assess white cell count by looking at 4 fields across the film.
  4. Manual platelet count- estimated by counting a quarter of a field x10
44
Q

What is rheology?

A

•Provides information of the physical properties of the blood and is therefore unlike other tests in that there is no measurement of a defined molecule or cell.

The 2 most common tests are erythrocyte sedimentation rate and plasma viscosity testing.

  1. Erythrocyte Sedimentation Rate (ESR)
  2. Plasma Viscosity (PV)- quantify proteins in patient plasma
45
Q

Erythrocyte sedimentation rate

A
  • Observes rate and fall of RBCs in plasma, expressed in mm/hour
  • Influenced by extent RBC form rouleux (aggregation)
46
Q

What is the Westergren method?

A

Measures the rate of gravitational settling over 1 hour of anticoagulated RBC’s from a fixed point in a tube of defined length and diameter in an upright position.

•Fall of RBC has 3 stages:

  1. Rouleux occurs
  2. Fall of cells
  3. Sedimentation at the bottom of the tube
47
Q

Plasma viscosity

A
  • Plasma drawn through capillary tube method
  • Run time between two points calculated
  • Demonstrates a parallel rise of ESR but only reflects protein component of the blood, esp those of large molecular size like fibrinogen
  • Low levels of fibrinogen and low plasma viscosity is shown neonates= physiological lower levels of protiens
  • Plasma viscosity is not affected by anaemia unlike ESR as only plasma investigated
  • Formation of fibrin clot invalidates results
48
Q

Plasma viscosity and their corresponding clinical indications

A
49
Q

FBC/ESR result

A

The top section has the demographic data of the patient and the hospital below it in the left hand column is the abbreviation of the particular test.

To the right are the results and units and the reference range in brackets, the sample date is on the lower right

50
Q

Results

A
  1. Results that are normal= sent out
  2. BMS checks any abnormal results outside reference range and checks if further tests need to be conducted
  3. If they fit the patient’s previous results/diagnosis they are released with a comment
51
Q

Reference range-bell shaped curve

A
  • Describes variation of measurement in an healthy individual.
  • Ideally locally defined (variation with analysers)
  • Reference interval mean +/- 2SD – range comprises of 2 SD on either side of the mean- 95% normal subjects
  • Some parameters age and sex needs to be taken into account (e.g. FBC)

Haematology and Transfusion (4 decks)

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