Practical 4: Investigation of Bone Function and Damage Flashcards
What is a bone profile?
A batch of biochemical blood tests grouped together as they are all related to bone disease
Why are bone profile’s carried out?
For the diagnosis and monitoring of metabolic bone disorders/bone disease
What are the four most common test in a bone profile?
Calcium
Albumin (notes in practical 3)
Phosphate
Alkaline phosphatase
What method is used to to calculate calcium concentration?
Arsenazo III Colourmetric method
Write a note on calcium in the body
(3)
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
What form is calcium in in the bones and teeth
Crystalline hydroxyapatite
What are calcium’s three forms in serum
Protein-bound (45%)
Ionised (45%)
Complexed with ligands (10%)
What ligands can calcium complex with?
(4)
Citrate
Lactate
Phosphate
Bicarbonate
What are the functions of calcium?
(5)
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
How does calcium regulate the activity of adenylate cyclase and phosphodiesterase
Through reversible combination with calmodulin
When might elevated levels of serum calcium be found?
(3)
Hyperparathyroidism
Carcinomas
Vitamin D overdoses
What might elevated levels of serum calcium indicate
Chronic renal disease
Acute pancreatic disease
When might low levels of serum calcium be seen?
(3)
Hypoparathyroidism
Vitamin D deficiency
Renal failure
What is the principle behind Arsenazo III
(3)
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
At what absorbance is the Arsenazo assay read?
650nm
How should your sample be prepared prior to measuring calcium concentration
(3)
Serum is recommended
Serum is stable for 8 hours at room temp
Serum is stable for 24hours between 2 and 8 degrees
What is your blank for the Arsenazo assay?
Water and reagent
How should you incubate your Arsenazo assay
5 minutes at room temp
What is the equation for corrected calcium?
Ca(corrected) = Ca(measured) + [(40-Alb) x 0.02]
Why might ALP be raised in relation to bone?
(2)
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
What is the principle behind the ALP assay
(2)
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
What is the blank for the ALP assay
Blank in air
At what absorbance is the ALP assay read?
405nm
How do you calculate ALP
Average absorbance per minute at 405nm x 2760 = ALP (IU/L)
