calcium (Ca+2) in serum/plasma

Reference interval

• Male & Female: 8.1 - 10.9 mg/dL (serum)

Principle

The Kodak Ektachem Clinical Chemistry Slide (Ca) is a dry multilayered analytical element coated on a transparent polyester support.

A 10 uL drop of sample deposited on the slide is evenly distributed on the reflective polymer spreading layer. The bound Ca+2 is dissociated from binding proteins, allowing the Ca+2 to penetrate through the spreading layer into the underlying dye- mordant layer. There, the Ca+2 forms a complex with Arsenazo III dye, causing a shift in the absorption maximum.

The mordant binds with the dye, preventing migration into the spreading layer after the serum sample is deposited on the slide.

After incubation, the reflection density of the colored complex is measured spectrophotometrically.

The amount of colored complex formed is proportional to the amount of Ca+2 present in the sample.

The following reaction sequences are involved:

Ca2+  + Arsenazo III  -----------> pH 5.6 colored Complex

Clinical significance

• in the circulation Ca+2 is
  • bound to protein (45%)
  • in the free ionized form (45%)
  • complexed to anions (10%)
• albumin is the major serum protein binding Ca+2
• reference intervals for serum Ca+2 assume a normal serum albumin
• a 'corrected' Ca+2 (for diminished albumin) may be estimated by the equation:

Corrected Ca+2 = 0.8 x (4 - [[[A13149|serum albumin]] (g/dL)]) + serum Ca+2

• Ca+2 is the major mineral component of bone
  • 99% of the body's Ca+2 is in bone
• plasma Ca+2 plays role in
  • transmission of nerve impulses
  • maintaining normal muscle contraction
• abnormal concentrations of serum Ca+2 may indicate
  • malfunction of the parathyroid glands
  • bone diseases
  • carcinoma
  • malnutrition & (or) malabsorption syndrome
  • vitamin D deficiency
  • overdose with Ca+2-containing antacids
  • renal diseases

Increases

• see hypercalcemia
• pharmaceutical agents:
  • in vivo effects
    • androgens, calciferol, dihyrotachysterol, progestins, estrogens, thiazides
    • calcium & vitamin D supplementation in postmenopausal women

Decreases

• see hypocalcemia
• hypoalbuminemia
• pharmaceutical agents:
  • in vivo effects
    • acetazolamide, corticosteroids, mithramycin
  • chemical interferences
    • citrate, EDTA

Specimen

Collect the specimen using standard venipuncture technique, without stasis, & remove promptly from the clot. Lithium or sodium heparin may be used as an anticoagulant for plasma specimens.

Special Precautions: Do not use collection tubes containing fluoride, oxalate, citrate, or EDTA because these substances chelate Ca+2 causing significantly lower results.

Prolonged contact with the clot may cause lowered Ca+2 values.

Handle specimens in stoppered containers to avoid contamination and evaporation. Specimens must be allowed to reach room temperature prior to analysis. If possible, place at least 100 uL of sample in the sample cup & analyze within 15 minutes of filling the cup. Refrigerate samples at 2-8 degrees C for up to 24 hours.

Minimum sample size of 0.5 milliliter with an optimum size of 1.0 milliliter or larger.

More general terms

• calcium in body fluid

More specific terms

• calcium in serum post challenge

Additional terms

• Ca+2
• calcium phosphate product (Ca-P product)
• hypercalcemia
• hypocalcemia
• ionized Ca+2 in serum/plasma/blood

Component of

• chemistry 8 panel (basic metabolic panel, BMP, basic chemistry panel)
• chemistry 8 panel with ionized calcium; basic metabolic panel (BMP) with ionized calcium
• chemistry 14 panel (comprehensive metabolic panel, CMP, chem 12, SMA12, SMA20)
• calcium/sodium in serum/plasma
• calcium/protein in serum/plasma
• calcium/phosphate in serum/plasma
• calcium/albumin in serum/plasma
• chronic kidney disease panel
• parathyroid panel
• pancreatic panel
• coma panel
• bone/joint panel

Patient information

calcium (Ca+2) in serum/plasma patient information