Clinical background:
Ionised calcium is the physiologically active form of calcium circulating in the body, approximately 47% of the total.
Specimen container paediatric:
Serum (SST or plain tube)
Specimen container adult:
Serum (SST or plain tube)
Minimum volume paediatric:
1 mL blood
Minimum volume adult:
2 mL blood
Special requirements:
Send the sample to the lab immediately after collection.
Sample stability:
30 minutes from collection.
Reference ranges:
>1 year: 1.15 – 1.27 mmol/L
Factors affecting result:
EDTA, oxalate and citrated samples are unsuitable
The distribution of calcium between being protein-bound or in free solution is dependent on H+ concentration (pH). Because this can change in vitro, measurements of free calcium should be made rapidly after the blood has been drawn and ideally be performed within 30 minutes, longer if the sample is kept at 4 deg C.
Other info:
Lithium heparin plasma sample also acceptable