Endocrine Abstracts

Background: C-peptide is an amino-acid chain which is an equimolar marker of endogenous insulin. It is used to investigate the cause of non-diabetic hypoglycaemia and classification of diabetes. C-peptide can only be interpreted with a paired venous glucose <3 mmol/l for non-diabetic hypoglycaemia, and >4 mmol/l for diabetes classification.

Aims and Objectives: To determine if: 1. C-peptide tests were requested for appropriate indication 2. Tests were requested with clear information 3. Samples were sent with a paired venous glucose 4. Tests were analysed appropriately as indicated by paired glucose 5. Tests were done with paired insulin for investigation of hypoglycaemia.

Methodology: We completed an audit using data collected from the Royal Bournemouth Hospital (RBH) laboratory. We obtained 320 C-peptide requests, for 130 patients, over 35-month period and analysed according to the objectives.

Results: 92.3% of patients had an appropriate indication for C-peptide test; investigation for hypoglycaemia (29.2%) or classification of diabetes (61.5%). Only 91.6% had a clear description on request form. From the 320 C-peptide requests, only 83.5% were sent with a paired glucose. Of the 196 requests for hypoglycaemia, 19.4% were analysed with a glucose >3 mmol/l or without a paired glucose, and 16.7% weren’t paired with insulin. As for diabetes classification, of the 90 C-peptide requests, only 67.8% were analysed with a glucose >4 mmol/l.

Conclusion: We found that none of our objectives met the gold standard of 100%. In response, we have discussed our results with the RBH laboratory, to update their glucose cut-off for C-peptide analysis in both hypoglycaemia and diabetes. This audit aims to educate both medical and laboratory staff to request C-peptides only for appropriate indications, to describe clear clinical details, to send all tests with a paired glucose (and insulin for hypoglycaemia) and to process all investigations with an appropriate glucose level.