Indications:
The measurement of plasma calcium is useful whenever the suspected disorder of calcium metabolism, whether from bone – primary storage location – or bowel, kidney or regulating hormones.
Principle:
In plasma, calcium exists in several forms:
– Calcium not ultra-filterable bound to plasma protein: 45%;
– Ultra-filterable calcium, divided into:
– Ionized calcium, physiologically active 50%
– Bound calcium to citrate, phosphate and bicarbonate: 5%.
Parathyroid hormone is hypercalcémiante and prevents bone mineralization.
Calcitonin is hypocalcémiante and promotes calcium deposition on the bone.
Vitamin D is hypercalcémiante and promotes bone deposition of calcium.
Technique:
Sampling 5 mL venous blood lithium heparin, away from a meal.
The patient must lie down.
Dosing is by spectrometry.
Results:
The usual values are between 90 and 105 mg / L, 2.2 to 2.6 mmol / L.
However, these results should take into account the serum protein: a higher rate increases in serum calcium;conversely, a lower rate decreases.
There is talk of hypercalcemia to a rate higher than 105 mg / L.
if it is observed:
– Bone metastases;
– Primary hyperparathyroidism;
– Sarcoidosis.
There is talk of hypocalcemia for a rate lower than 90 mg / L.
if it is observed:
– Hypoparathyroidism after surgery or primary;
– Vitamin D deficiency:
– Contributed by deficiency
– By absorption disorder,
– By vitamin D deficiency transformation active metabolite.
If hypocalcemia is confirmed, should be measured creatinine and phosphate:
– If hyperphosphatemia is observed, it is:
– renal failure,
– Hypoparathyroidism;
– If, however, there hypophosphatemia is osteomalacia.
Cost:
B15.
Practical advice:
Pregnancy, postpartum, birth control pills are down 20% in serum calcium.
Before symptoms of tetany, the review has no diagnostic value.
