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) |
