Common Causes of Spurious Results

Problem

Common Causes

Affected Analyte

Delay in processing

Overnight storage
>6 hour delay in separation

Increased K⁺, PO₄, LDH, AST

Incorrect storage

Storing unseparated sample in the fridge

Increased K⁺, PO₄,

Decreased HCO₃

Haemolysis

Expelling blood through needle
Vigorous shaking
Extreme temperature

Increased K⁺, PO₄, AST, LDH

Inappropriate Collection Site

Sample taken from drip arm

Increased drip analyte e.g. K⁺, glucose

Decreased analytes - dilutional effect

Incorrect container or anticoagulant

No fluoride oxalate

Decreased glucose

EDTA contamination

Increased K⁺

Decreased Ca⁺⁺, Mg⁺⁺, AlkP

Lithium heparin tube

Increased lithium

Effect of Haemolysis, Lipaemia and Icterus:

Haemolysis, lipaemia and icterus may cause false elevations or reductions in the measured concentrations of several biochemistry analytes. The presence of haemolysis, lipaemia or icterus will be detected in the laboratory and the affected analytes will be flagged. In cases where there is significant interference, the affected analyte will not be reported. Further information can be obtained from the Duty Biochemist (291 2136).

Problem	Common Causes	Affected Analyte
Delay in processing	Overnight storage >6 hour delay in separation	Increased K⁺, PO₄, LDH, AST
Incorrect storage	Storing unseparated sample in the fridge	Increased K⁺, PO₄, Decreased HCO₃
Haemolysis	Expelling blood through needle Vigorous shaking Extreme temperature	Increased K⁺, PO₄, AST, LDH
Inappropriate Collection Site	Sample taken from drip arm	Increased drip analyte e.g. K⁺, glucose Decreased analytes - dilutional effect
Incorrect container or anticoagulant	No fluoride oxalate	Decreased glucose
	EDTA contamination	Increased K⁺ Decreased Ca⁺⁺, Mg⁺⁺, AlkP
	Lithium heparin tube	Increased lithium