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) |