Calcium, Urine

Diagnostic Use

Calcium is an electrolyte which plays an important role in many physiological processes throughout the body. In normal health, almost all of the filtered calcium is reabsorbed in the post-glomerular nephron.

Urinary calcium excretion exhibits diurnal variation, largely reflecting dietary intake. As such, a 24 hour collection is the best way to assess urine calcium status.

Department

Core Biochemistry

Delphic Registration Code

UCA

Turnaround Time

3 hours

Test Code

4200

Specimen Type

• Urine
• 24hr Urine

Specimen Requirements

Tube/Container Type:

Preferred

• 24hr Urine Container

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• 24hr Urine Container

Preferred Sample Volume (ml)

0.5

Additional Specimen Information

24 hour urine collection over acid. Measurement errors are possible when not collected over acid.
Can be measured on the same urine collected for Magnesium and Phosphate.

Aliquot Instructions

Sample Type

• Urine

Transport to Lab

Ambient (8 - 24 degrees Celsius)

Additional Referral/Aliquot Information

Aliquot Instructions: 5 mL Urine preserved with HCl during collection. Ensure urine is homogenised by mixing well before taking the sampling aliquot

Interpretation

Hypercalciuria increases the risk of developing kidney stones.  Urine calcium measurement is included as part of a “stone screen” in patients with unexplained nephrolithiasis or nephrocalcinosis.  Because of the large intra-individual variation in urinary calcium excretion, it is recommended to measure urine calcium on several separate timed urine collections.

Urine calcium measurement may also be measured to calculate the fractional excretion of calcium (FECa) in patients with hyperparathyroidism.  FECa is elevated in patients with primary hyperparathyroidism, but is low in patients with familial hypocalciuric hypercalcaemia (FHH).

Causes of hypercalciuria include hyperparathyroidism, type 1 renal tubular acidosis, Paget’s disease, malignancy, prolonged immobilisation and autosomal dominant hypocalcaemia.

Causes of hypocalciuria include FHH and thiazide diuretics.

Reference Intervals

2.5 – 7.5 mmol/24hr

Test Method

Performed on Beckman Coulter AU5822 analyser using Beckman Coulter reagents.

Non-Funded Test Cost

$8.23 (Exclusive of GST)

Billing Code

4200

Contact Information

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