Biosystems Calcium MTB
PRINCIPLE OF THE METHOD
Calcium in the sample reacts with methylthymol blue in alkaline medium forming a coloured complex that can be measured by spectrophotometry. Hydroxyquinoline is included in the reagent to avoid magnesium interference1,2.
- A. Reagent. Potassium cyanide 7.7 mmol/L, ethanolamine 1.5 mol/L.
- B. Reagent. Methylthymol blue 1 mmol/L, hydrochloric acid 10 mmol/L, hydroxyquinoline 17 mmol/L.
- S. Calcium/Magnesium Standard. Calcium 10 mg/dL (2.5 mmol/L), magnesium 2 mg/dL.
Store at 15-30°C.
Reagents and Standard are stable until the expiry date shown on the label when store d tightly closed and if contaminations are prevented during their use.
Indications of deterioration:
– Reagents: Presence of particulate material, turbidity, absorbance of the blank over 0.800 at 610 nm.
– Standard: Presence of particulate material, turbidity.
Standard (S) is provided ready to use.
Working Reagent: Mix equal volumes of Reagent A and Reagent B (Note 1). Mix gently. Stable for 2 days at 2-8
Serum and plasma3: 8.6-10.3 mg/dL = 2.15-2.58 mmol/L Urine3: 100-300 mg/24-h = 2.5-7.5 mmol/24-h
These ranges are given for orientation only; each laboratory should establish its own reference
It is recommended to use the Biochemistry Control Serum level I (cod. 18005, 18009 and 18042) and II (cod. 18007, 18010 and 18043) to verify the performance of the measurement procedure.
Each laboratory should establish its own internal Quality Control scheme and procedures for corrective action if controls do not recover within the acceptable tolerances.
Detection limit: 0.6 mg/dL calcium = 0.15 mmol/L calcium.
Linearity limit: 15 mg/dL calcium = 3.75 mmol/L calcium. For higher values dilute sample 1/2 with distilled water and repeat measurement.
Sensitivity: 30 mA.dL/mg = 120 mA.L/mmol
Trueness: Results obtained with this reagent did not show systematic differences when compared with reference reagents (Note 3). Details of the comparison experiments are available on request.
Interferences: Hemolysis (hemoglobin < 10 g/L) and bilirubin (< 20 mg/dL) do not interfere. Lipemia (triglycerides > 1.25 g/L) interfere. Other drugs and substances may interfere4.
These metrological characteristics have been obtained using an analyzer. Results may vary if a different instrument or a manual procedure are used.
Calcium is the most prevalent cation found in the body, distributed in bone (99%), soft tissues and extracellular fluid. Its concentration in plasma is regulated by parathyroid hormone, vitamin D and calcitonin.
Calcium ion is important in the transmission of nerve impulses, in the maintenance of normal muscle contractility, as a cofactor in certain enzyme reactions, and in the coagulation of the blood.
Hypercalcemia can be due to vitamin D intoxication, enhanced renal retention, osteoporosis, sarcosidosis, thyrotoxicosis, hyperparathyroidsm, multiple mieloma, idiopathic hypercalcemia of infancy, and carcinoma metastasic to bone3,5.
Elevated calcium concentration in urine is found in nephrolithiasis and metabolic acidosis3,5. Hypocalcemia may be caused by primary and secondary hypoparathyroidism,
pseudohypoparathyroidism, vitamin D deficiency, malnutrition and intestinal malabsorption3,5.
Clinical diagnosis should not be made on the findings of a single test result, but should integrate both clinical and laboratory data.
- 1. Contamination of glassware with calcium will affect the test. Use acid-washed glassware or plastic tube
- 2. These reagents may be used in several automatic analysers. Instructions for many of them are available on request.