9. Bone Flashcards
Best anti-coagulant for calcium analysis specimens
Heparin if plasma
NO EDTA, CITRATE, OXALATE
Serum best
Why is pH an important consideration in ionized calcium determinations
- Decreased pH = Ca2+ dissociates from its complexes forms = increases amount of free ionized Ca2+ in serum
Softening of bone due to defective bone mineralization (formation of osteoid)
Osteomalacia
How is ionized calcium measured?
Measured by ion selective electrodes (ISEs)
What reagent is used to determine the concentration of serum inorganic phosphate?
Ammonium molybdate
What is the most common cause of hypercalcemia?
Primary hyperparathyroidism
What substances regulate calcium levels?
- PTH
- Calcitonin
- Vitamin D
3 main regulators of Ca2+/PO4-/Mg2+
- PTH
- Calcitonin
- Vitamin D
A patient exhibits signs of tetany but her ionized calcium is normal. What other analyte should be checked?
Mg2+
Low levels also cause tetany
Where is PTH produced and what is its main action
- Produced in parathyroid glands
- Increases serum Ca2+ and decreases phosphates
- PTH increased in primary hyperparathyroidism
- PTH decreased in hypothyroidism
How does hyperparathyroidism affect the level of serum phosphorus?
Decreases it
What does the lab measure to detect excess bone formation?
Alkaline phosphatase
Which anticoagulants cause a false DECREASE in Ca2+? How?
- EDTA
- Citrate
- Oxalate
All prevent coagulation by chelating Ca2+
What is the REFERENCE method for total calcium?
Atomic absorption
What is tetany?
Muscle spasms, cramps, irritability due to decreased Ca2+/Mg2+
