Blood - An introduction to clinical use

Question 1

what are the components of blood?

Answer 1

cellular component:

a) erythrocytes - 45%
b) buffy coat - leukocytes (wbc) and thrombocytes (platelets) - <1%

non-cellular component:

plasma - 55%

Question 2

what are the components of plasma?

Answer 2

• water - 95%
• proteins: albumin
• small organic molecules (glucose)
• minerals
• hormones
• excretory products (co2 - transported as bicarbonate)
• blood cells - rbc

Question 3

doe plasma components stay same / change?

Answer 3

undergo plasma homeostasis:

• composition of plasma is kept at relatively constant levels
• (e.g. fluid-electrolyte balance)

BUT ALSO:

Substances may be removed / added:

-e.g. glucose into blood from gut

Question 4

what are the cellular elements of blood?

Answer 4

RBC - 45 %

WBC:

• monocytes
• lymphocytes
• eosinophils
• neutrophils

Platelets (cell fragments)

Question 5

how are the cellular components of blood controlled?

Answer 5

composition of cellular element of blood undergoes cellular homeostasis

Question 6

how do you test for the cells that make up your blood?

Answer 6

complete blood count

Question 7

what are ways you can test blood glucose? (3)

Answer 7

fasting glucose test - (not eating / drinking anything other than water for 8hrs)

glucose tolerance test - after fasting and again after 2 hours after being given a glucose drink

glycated haemoglobin test (HbA1C) - measure of average blood sugar level over past 3 months.

Question 8

how do you measure the levels of oxygen and carbon dioxide in the blood?

• what does it show ?

Answer 8

Arterial Blood Gas (ABG)

• also tests pH
• blood sample from artery in wrist (painful)
• flags pH imbalances -> indicats life threat. respiratory or metabloic disorders

Question 9

what is a full blood count?

Answer 9

provides details about many of the different components of bloods: really useful !

Question 10

explain the test you do to evaluate difference types of cells?

how do you do it?

what does it show?

Answer 10

Peripheral Blood smear / blood film: to distinguish between the different types of WBCs, and to determine their relative percentages in the blood; to help detect, diagnose, and/or monitor a range of deficiencies, diseases, and disorders involving blood cell production, function, and lifespan

• drop of blood on a glass slide
• stained
• represents a snapshot of cells in blood at the time
• size, shape and colour of RBC and WBC can be measured
• number of platelets est.

Question 11

what is a blood culture used to test for?

when do you use?

usually collected as what?

Answer 11

Blood culture:

• used when think have an infection: test for pathogens

- vein blood sample taken

• blood culture bottles collected as aerobic and anaerobic

Question 12

what determines the liklihood of false negatives and false positives?

Answer 12

specificity and sensitivity will determine liklihood of false negatives / positives

Question 13

what do you have to consider with blood tests?

Answer 13

within the patients personal circumstances, past medical history, currrent medication and any other investigations

Question 14

what do reference ranges show?

Answer 14

ranges will often represent the values found in 95% of individuals in the chosen reference group

(use reference range NOT normal range)

Question 15

what need to consider with reference ranges?

Answer 15

what is ‘normal’ for one group is not nec. normal for another group - need a panel of tests to build up picture