Turnaround times
The quoted turnaround time is from sample receipt in the laboratory, to results authorisation in the Laboratory Information Management system. The times do not include transport of specimen to the laboratory or the administrative process to print and post/email reports. Service users must allow for transport and reporting time when ordering tests.
Clinical background:
Blood calcium levels are tightly regulated within a narrow range and circulates in three main forms:
• Ionised calcium (physiologically active) at ~47%
• Albumin bound calcium at ~46%
• Complexed (with citrate, phosphate etc) at ~7%
As calcium is ~46% albumin bound an adjusted calcium value is also calculated and reported to make allowance for albumin concentration in the sample The formula used for the calculation is:
Adjusted serum calcium = Total serum calcium + ((47.2-serum albumin) x 0.0127)
The references ranges for adjusted and total serum calcium are the same.
Because a significant portion of calcium is bound to albumin, any alteration in the level of albumin will affect the level of calcium is measured.This calculation is an approximation and is invalid at extreme concentrations of albumin, typically <20g/L. Direct measurement of ionised calcium is advisable in these cases.
Specimen container paediatric:
Serum (SST or plain tube)
Specimen container adult:
Serum (SST or plain tube)
Minimum volume paediatric:
0.5 mL blood
Minimum volume adult:
1 mL blood
Sample stability:
Unseparated sample:
2 days
Separated sample:– 7 days at 15 to 25C- 3 weeks at 4ºC- 8 months at -20C
Reference ranges:
Age up to 4 weeks: 2.0 – 2.7 mmol/L
Age 4 weeks to 16 years: 2.2 – 2.7 mmol/L
Age 16 years and over: 2.2 – 2.6 mmol/L
Factors affecting result:
EDTA, oxalate and citrated samples are unsuitable
Blood for measurement of total calcium should ideally be drawn from a vein in which the blood is free-flowing (that is, without a tourniquet).
Other info:
lithium heparin plasma sample also acceptable