Clinical background:
In normal subjects, circulating NEFA and ketone body concentrations rise simultaneously during fasting. Published data on normal fasting children suggests that log [NEFA] and log total [ketone bodies] are linearly related. A rise in the NEFA concentration out of proportion to the rise in ketone bodies is suggestive of a defect of b-oxidation or ketone body synthesis. During hypoglycaemia a low circulating NEFA and ketone bodies suggests hyperinsulinism.
Specimen container paediatric:
EDTA plasma
Specimen container adult:
EDTA plasma
Minimum volume paediatric:
1 mL blood
Minimum volume adult:
2 mL blood
Special requirements:
To investigate cause of hypoglycaemia, collect sample during a hypoglycaemic episode or following a monitored prolonged fast.Lithium heparin sample is NOT acceptable.
Sample stability:
Unseparated whole blood 4 hours at 4°CSeparated plasma or serum 2 months at -20°C
Transport requirements:
Local (NuTH) requests: Send samples to the laboratory at ambient temperature. Samples should be forwarded to the RVI for processing. N.B. Check if other tests (e.g. blood spot acylcarnitines) are required before processing the sample.External requests: send frozen plasma or serum to RVI.
Reference ranges:
When analysed as part of an intermediary metabolite profile, results are reported with an interpretative comment.
Reference ranges are otherwise as follows:
Non-fasting: < 0.9 mmol/L
Fasting (overall range): 0.5 – 2.8 mmol/L
15h fast: 0.5 – 1.6 mmol/L
20h fast: 0.6 – 2.6 mmol/L
24h fast: 1.0 – 2.8 mmol/L
Factors affecting result:
Heparin (stimulates lipoprotein lipase therefore NEFA release from triglycerides).
Haemolysis