Ionised calcium can be either a venous or arterial specimen collected into a heparinised syringe (same as used for arterial blood gas collection). All air bubbles should be expelled from the syringe immediately after collection.
Send specimen ASAP to laboratory on a cold pack. Specimen is stable for up to 4 hours if kept cold.
Ionised calcium is only required with PTH if specifically requested by the Clinician.
APPLICATION: Ionised calcium is recommended when PTH is being measured, if complexed calcium is likely to be very high (eg, during massive transfusion), if pH is abnormal or if an abnormality in calcium is marginal.