Practical 4: Investigation of Bone Function and Damage

Question 1

What is a bone profile?

Answer 1

A batch of biochemical blood tests grouped together as they are all related to bone disease

Question 2

Why are bone profile’s carried out?

Answer 2

For the diagnosis and monitoring of metabolic bone disorders/bone disease

Question 3

What are the four most common test in a bone profile?

Answer 3

Calcium
Albumin (notes in practical 3)
Phosphate
Alkaline phosphatase

Question 4

What method is used to to calculate calcium concentration?

Answer 4

Arsenazo III Colourmetric method

Question 5

Write a note on calcium in the body
(3)

Answer 5

Fifth most abundant element in the body

Most calcium in adults is extracellular and 99% of it exists as crystalline hydroxyapatite in bones and teeth

Calcium has three forms in serum: protein-bound, ionised and complexed with ligands

Question 6

What form is calcium in in the bones and teeth

Answer 6

Crystalline hydroxyapatite

Question 7

What are calcium’s three forms in serum

Answer 7

Protein-bound (45%)

Ionised (45%)

Complexed with ligands (10%)

Question 8

What ligands can calcium complex with?
(4)

Answer 8

Citrate

Lactate

Phosphate

Bicarbonate

Question 9

What are the functions of calcium?
(5)

Answer 9

Nerve impulse transmission

Muscular contraction

Blood coagulation

Regulating the activity of adenylate cyclase and phosphodiesterase through reversible combination with calmodulin

Extracellular ionised calcium concentration on the cell surface controls secretion from parathyroid glands, thyroid C cells and pancreatic B cells

Question 10

How does calcium regulate the activity of adenylate cyclase and phosphodiesterase

Answer 10

Through reversible combination with calmodulin

Question 11

When might elevated levels of serum calcium be found?
(3)

Answer 11

Hyperparathyroidism

Carcinomas

Vitamin D overdoses

Question 12

What might elevated levels of serum calcium indicate

Answer 12

Chronic renal disease

Acute pancreatic disease

Question 13

When might low levels of serum calcium be seen?
(3)

Answer 13

Hypoparathyroidism

Vitamin D deficiency

Renal failure

Question 14

What is the principle behind Arsenazo III
(3)

Answer 14

Arsenazo III specifically binds to calcium forming a coloured complex which can be measured at 650nm

Ca++ + Arsenazo = coloured complex

The amount of calcium present is directly proportional to the intensity of the coloured complex

Question 15

At what absorbance is the Arsenazo assay read?

Answer 15

650nm

Question 16

How should your sample be prepared prior to measuring calcium concentration
(3)

Answer 16

Serum is recommended

Serum is stable for 8 hours at room temp

Serum is stable for 24hours between 2 and 8 degrees

Question 17

What is your blank for the Arsenazo assay?

Answer 17

Water and reagent

Question 18

How should you incubate your Arsenazo assay

Answer 18

5 minutes at room temp

Question 19

What is the equation for corrected calcium?

Answer 19

Ca(corrected) = Ca(measured) + [(40-Alb) x 0.02]

Question 20

Why might ALP be raised in relation to bone?
(2)

Answer 20

ALP is elevated in any condition that affects bone growth and in bone disease associated with increased osteoblastic activity

ALP can be used to help detect certain types of cancer that may have spread to the bone and bone conditions such as Paget’s disease where the bone has become deformed

Question 21

What is the principle behind the ALP assay
(2)

Answer 21

ALP catalyses the transphosphorylation of p-nitrophenylphosphate (p-NPP) to p-nitrophenol (p-NP)

The change in absorbance at 405nm due to the formation of p-NP is directly proportional to the ALP activity

Question 22

What is the blank for the ALP assay

Answer 22

Blank in air

Question 23

At what absorbance is the ALP assay read?

Answer 23

405nm

Question 24

How do you calculate ALP

Answer 24

Average absorbance per minute at 405nm x 2760 = ALP (IU/L)