Background: The hallmark of congenital hyperinsulinism (CHI) is the demonstration of detectable plasma insulin during hypoglycaemia. Insulin can be undetectable in a significant proportion of patients with CHI. Plasma samples for insulin requires rapid and careful handling for reliable results. There is little published data on the value of C-peptide in the diagnosis of CHI.
Objective and hypotheses: To assess the usefulness of C-peptide in the diagnosis of CHI.
Method: All completed hypoglycaemia (laboratory glucose <2.6 mmol/l) screening tests undertaken at a tertiary referral centre over a 4-year period were assessed retrospectively. The diagnosis of CHI was made on a combination of glucose requirement >8 mg/kg/min, detectable insulin during hypoglycaemia, suppressed ketones and a glycaemic response to glucagon. The plasma C-peptide concentration during hypoglycaemia in patients with CHI was compared with that of the patients with other diagnoses.
Results: 60 results were available from 41 patients. Median age was 16 months (1 day20.5 years). Diagnoses included 23 CHI, one GH deficiency, one peroxisomal disorder, one respiratory chain disorder, and 15 ketotic hypoglycaemia. The concentration of plasma C-peptide in patients with CHI was significantly higher than that for patients with a diagnosis other than CHI as shown in Fig. 1 (P<0.001). The positive predictive value for a diagnosis of CHI with C-peptide concentration of 350 pmol/l is 96.7% and the negative predictive value is 80%.
Conclusion: A plasma C-peptide concentration of >350 pmol/l during hypoglycaemia could be used to differentiate CHI from other causes of hypoglycaemia especially when plasma insulin level is low or could not obtained.
18 Sep 2014 - 20 Sep 2014