Blood - An Intro to Clinical Use

Question 1

What are examples of biological substances contained in blood?

Answer 1

Ions, proteins, fats, respiratory gases, hormones, cells

Question 2

What are 3 functions of blood?

Answer 2

Immunological, haemostasis/clotting, regulation of body temperature

Question 3

What are the 3 components of blood and what percentage of total blood is each?

Answer 3

Plasma - 55%
Buffy coat (leukocytes (white blood cells) and thrombocytes (platelets)) - <1%
Erythrocytes (red blood cells) - 45%

Question 4

What is average blood volume of 70kg man?

Answer 4

5.5L

Question 5

What percentage of plasma is water?

Answer 5

95%

Question 6

What are the components of blood plasma?

Answer 6

Water
Proteins (main one is albumin)
Small organic molecules (e.g. glucose)
Mineral ions (e.g. sodium, chloride)
Hormones
Excretory products (e.g. carbon dioxide, largely transported as bicarbonate in plasma)
Blood cells (e.g. red blood cells contain haemoglobin which transports oxygen)

Question 7

What is an example of plasma homeostasis?

Answer 7

Fluid-electrolyte balance

Question 8

What is the concentration of sodium in the plasma?

Answer 8

133-146 mmol/L

Question 9

What is an example of a situation where a substance that may be present in varying concentrations as it is added or removed from the plasma?

Answer 9

Absorption of glucose into the gut

Question 10

What organs may have conditions that disturb the balance in the plasma?

Answer 10

Kidney, lungs, liver

Question 11

What are platelets?

Answer 11

Formed elements consisting of membrane-enclosed packets of cytoplasm
Involved in clotting response to seal leaks in damaged or broken blood vessels

Question 12

What are the 5 types of white blood cells?

Answer 12

Monocytes - phagocytes similar to the free macrophages in other tissues
Lymphocytes - uncommon in blood but dominant cell type in lymph
Eosinophils and neutrophils - phagocytes
Basophils - promote inflammation much like mast cells in other tissues

Question 13

What is a complete blood count?

Answer 13

Test that counts the cells that make up your blood

Question 14

What are the normal white cell/leukocyte counts?

Answer 14

White cell/leukocyte (3.8 – 10.0 x 10-9/L) 
WITH
Neutrophils (2.0–7.5 x 10-9/L)  
Lymphocytes (1.1–3.3 x 10-9/L)  
Monocytes (0.2-1.0 x 10-9/L)  
Eosinophils (0–0.4 x 10-9/L)  
Basophils (0-0.1 x 10-9/L)

Question 15

What could a raised leukocyte count indicate?

Answer 15

Inflammation or infection

Question 16

Blood tests contribute to what percentage of clinical diagnoses?

Answer 16

60-70%

Question 17

What are 3 ways that blood tests can be used?

Answer 17

Helping to diagnose a condition, assessing the health of certain organs or screening for some genetic conditions.

Question 18

What must be considered when interpreting a blood test?

Answer 18

The patient’s personal circumstances, past medical history, current medication and the results of any other investigations

Question 19

What are 15 examples of blood tests?

Answer 19

Blood cholesterol test 
Blood culture 
Blood gases test 
Blood glucose (blood sugar) tests 
Blood typing 
Cancer blood tests 
Chromosome testing (karyotyping) 
Coagulation tests 
C-reactive protein (CRP) test 
Electrolyte test 
Erythrocyte sedimentation rate (ESR) 
Full blood count (FBC) 
Genetic testing and screening 
Liver function test 
Thyroid function test

Question 20

What are 3 examples of blood glucose tests?

Answer 20

• fasting glucose test –the level of glucose in blood is checked after fasting (not eating or drinking anything other than water) for at least 8 hours
• glucose tolerance test – the level of glucose in your blood is checked after fasting, and again 2 hours later after being given a glucose drink
• Glycated haemoglobin (HbA1C) test – as a measure of the average blood sugar level over the past 3 months

Question 21

What is a blood gases test used to assess?

Answer 21

Levels of oxygen and carbon dioxide, as well as balance of acid and alkali in blood

Question 22

How is a blood gases sample obtained?

Answer 22

Taken from an artery, usually at the wrist

Likely to be painful and only carried out in hospital

Question 23

What is one of the most commonly requested blood tests?

Answer 23

Full blood count

Question 24

What does a peripheral blood smear/blood film evaluate?

Answer 24

White blood cells, red blood cells and platelets

Question 25

How is a blood film produced?

Answer 25

Single drop of blood spread in thin layer across glass slide, dried, then stained with special dye

Question 26

What is a blood film?

Answer 26

A blood film is a snapshot of the cells that are present in the blood at the time that the sample is obtained

Question 27

What can be measured, and what can be estimated, by a blood film?

Answer 27

The size, shape and colour (indicators of haemoglobin content) of the RBCs and WBCs can be measured and the number of platelets estimated

Question 28

When is a blood culture used?

Answer 28

When an infection is suspected

Question 29

What does a blood culture test for?

Answer 29

Presence of pathogens (e.g. bacteria)

Question 30

What does a blood culture involve?

Answer 30

Taking a small sample of blood from (for example) a vein in the arm

Question 31

How are blood cultures analysed?

Answer 31

The samples are analysed in the laboratory by incubation (e.g. on plates containing nutrients) for detection of specific microorganisms. Blood culture bottles are usually received as a pair; one aerobic and one anaerobic bottle, making a blood culture set.

Question 32

Which parameters in any test will determine the likelihood or false negatives and false positives?

Answer 32

Specificity and sensitivity

Question 33

What 4 sources are critical to the diagnostic process?

Answer 33

Patient interview Physical exam Medical history Medical tests

Question 34

What is a reference range?

Answer 34

Test results are commonly interpreted against population-based reference (normal) intervals – usually provided as part of a laboratory report Ranges will often represent the values found in 95% of individuals in the chosen ‘reference’ group In other words, even in a “normal” population, a test result will lie outside the reference range in 5% of cases (1 in 20) This is why the term “reference range” is preferred over “normal range”

Question 35

How do haemoglobin levels differ between men and women?

Answer 35

Women have means levels approximately 12% lower than men Male = 130-175 g/L Female = 115-150 g/L

Question 36

How do haemoglobin levels differ between male and female children?

Answer 36

Haemoglobin levels are identical in male and female infants and childhood – differences only begin to emerge in adolescence, probably due to hormonal differences