Factors known to significantly affect performance of tests/interpretation of results

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Problem Causes Affected analyte
Delay in processing
  • Overnight storage
  • >6 hour delay in separation
Increased potassium, phosphate, LDH, AST.
Incorrect storage Storing unseparated sample in the fridge
  • Increased phosphate and potassium
  • Decreased bicarbonate
Haemolysis
  • Expelling blood through needle
  • Vigorous shaking
  • Extreme temperature
Increased potassium, phosphate, LDH, AST.
Inappropriate Collection Site Sample taken from drip arm
  • Increased drip analyte e.g. sodium, glucose
  • Decreased analytes – dilutional effect
Incorrect container or anticoagulant No fluoride oxalate Decreased glucose
K-EDTA contamination
  • Increased potassium
  • Decreased calcium, magnesium, alkaline phosphatase
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.

Measurement uncertainty

All assays have a margin of error associated with the calculation of the numerical value. This is referred to as the measurement uncertainty and is usually expressed as a percentage of the reported
figure. This calculation allows the user to understand the uncertainty of any numerical results and can be assured with 95% confidence that the true result lies plus or minus the measurement uncertainty around the reported value. Further information on the measurement of uncertainty for all our laboratory assays is available by contacting the Duty Biochemist within routine working hours.

Point of Care

The relationship between values obtained in the laboratory and POCT are established and available upon request.

 

(Last reviewed February 2020)