Causes of spurious results

Results may not be reported if it is clear that the result is invalid. This list is not exhaustive; please contact the laboratory if in any doubt as to the validity of results. For example, methods using immunoassay can be subject to a range of interferences, including cross reactivity, for which the lab hold details.

Problem	Cause(s)	Effects
Delay in processing	Overnight storage, delay in transport, delayed analysis within lab	Potassium ↑, Phosphate ↑, Ammonia ↑, Bicarbonate ↓, BNP ↓, PTH ↓, Glucose ↓, ACTH ↓
Temperature	Storage of samples overnight in fridge, cold weather	Potassium ↑, Bicarbonate ↓
	Hot weather	Potassium ↓
Haemolysis	Poor collection technique, difficult to bleed, frozen storage, delayed transit/analysis	ACE, B12, Folate, Insulin, PTH, Vitamin D, Zinc not reported. Potassium ↑, Phosphate ↑, Ammonia ↑, AST ↑, LDH ↑
Icterus	Patient has liver disease	ACE (not reported)
Lipaemia (turbid sample)	Sample taken shortly after fatty meal	Sodium ↓
Incorrect sample site	Sample taken from drip arm	Drip arm analytes ↑, other analytes ↓
Incorrect sample tube	EDTA contamination	Potassium ↑, Calcium ↓, Magnesium ↓, ALP ↓, Zinc ↓
Light exposure	Inappropriate storage conditions	Bilirubin ↓, porphyrins ↓
Cross-reactivity	Interfering exogenous or endogenous substances	↑ or ↓, depending on methodology (most commonly affects drugs, hormones, tumour markers)