Chapter 2 Answers to self-check questions

2.1 The major differences between serum and plasma are:

  • serum is the fluid remaining after a clot has been removed from clotted blood, whilst plasma is the result of adding an anticoagulant to blood almost immediately after it has been obtained so that no clot is formed.
  • plasma has all coagulation proteins intact and allows the analysis of blood cells, whereas serum has lower levels of coagulation proteins and cannot be used for blood cell analysis.

2.2 The two major anticoagulants are EDTA and sodium citrate. EDTA is required by the FBC, whilst sodium citrate is required for coagulation tests. In some situations, blood for an ESR is taken into sodium citrate, whilst in others it can be measured in a sample anticoagulated with ETDA.

2.3 Those micronutrients important for the production of healthy blood cells include iron, folate, and vitamin B12.

2.4 Köhler illumination ensures optimal conditions for examining a specimen microscopically by maintaining a constant pattern of elimination across the entire field of view. This ensures all cells within the field are illuminated identically enabling fine cellular detail to be identified.

Select the ´10 objective lens;

Place a blood film on the stage and focus the microscope;

Reduce the field diaphragm so a small point of light can be seen through the eyepiece;

Adjust the condenser lens so the diaphragm is in focus;

Centre the field diaphragm under the condenser using the x and y condenser adjustment screws;

Open the field diaphragm just sufficiently to ensure the entire field of view is illuminated.

2.5 Both ELISA and LIA use capture antibodies immobilized on a solid phase; ELISA uses plastic/polystyrene wells and LIA uses latex particles. Addition of plasma to the latex particles leads directly to the end-point of agglutination, detected turbidimetrically. ELISA involves two more stages: addition of the tag antibody and then reaction with the substrate to generate the coloured product which is measured by spectrometry.

2.6 The red cell indices are MCV, MCH, and MCHC.

2.7 The two major groupings of white blood cells are polymorphonuclear leucocytes and mononuclear leucocytes. Polymorphonuclear leucocytes (neutrophils, basophils, and eosinophils) have an irregular lobed nucleus which can take on various forms (hence polymorphonuclear), whereas the lymphocyte nucleus is round and regular (hence mononuclear).

2.8 The two most common white blood cells are neutrophils (with an irregular nucleus and cytoplasmic granules) and lymphocytes (with a regular and round nucleus that occupies 95% to 99% of the cell—granules are absent).

2.9 The absolute count (´109/L) for each of the WBC species is as follows:

Neutrophils 10.24 ´ 109/L

Lymphocytes 3.36 ´ 109/L

Monocytes 1.92 ´ 109/L

Eosinophils 0.48 ´ 109/L

Basophils 0.00 ´ 109/L

Neutrophils, lymphocytes and monocytes are raised.

The patient is exhibiting a neutrophilia, lymphocytosis and monocytosis.

2.10 Platelets are small anucleate bodies arising from the megakaryocytes and which participate in haemostasis by forming a thrombus.

2.11 The two common tests of rheology are the ESR and plasma viscosity.

2.12 Vascular integrity promotes blood fluidity and also blood clotting upon vessel damage. The interactions of subendothelium–VWF–platelets, primary haemostasis, form the initial physical barrier. The platelet clot is strengthened by fibrin, the end-product of the coagulation reactions of secondary haemostasis. The clotting process is regulated by inhibitors and the clot broken down by autolysis and fibrinolysis once the wound has healed.

2.13 Prothrombin time (PT) assesses the extrinsic and common pathways. Activated partial thromboplastin time (APTT) assesses the intrinsic and common pathways. Fibrinogen can be directly quantified or assessed with the thrombin time.

2.14 Warfarin is monitored using the prothrombin time expressed as INR. Unfractionated heparin is monitored with the activated partial thromboplastin time.

2.15 Key haematinics are the micronutrients (iron, vitamin B12, and folate), and plasma proteins (such as transferrin and ferritin).

2.16 You should not use reference values from a textbook in your daily practice as they may be different from your local reference range. This may be due to several reasons, such as differences in autoanalyser performance and the fact that reference ranges may change over time.

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