Christiane Saddig, Achim AR Starke, Ralf Bender
Context and objective To evaluate the Cpeptide suppression test as a screening test in patients with symptoms of hypoglycemia as compared to the standard fasting test. Design Retrospective discriminant analysis of data from C-peptide suppression tests. Setting :Clinical study. Patients Two different sets: patients with insulinomas and patients without insulinomas but having symptoms compatible with hypoglycemia. Interventions The results from C-peptide suppression tests of 26 patients with insulinomas and 100 patients without insulinomas were compared. Main outcome measures A classification plot which introduces two discriminant parameters for the C-peptide suppression test: the ratio of [blood glucose]/[C-peptide] at the lowest C-peptide concentration and mean glycemia during insulin infusion. Results In patients with insulinomas, minimal serum C-peptide levels were higher (1.81±0.87 ng/mL; median 1.83 ng/mL; maximal suppression 37±24% of basal Cpeptide levels) as ompared to patients without insulinoma (0.40±0.15 ng/mL; median 0.30 ng/mL; maximal suppression of75±9%; P0.001). ean glycemia during the test was lower in patients with insulinomas (30.8±3.3 vs. 47.5±8.3 mg/dL; P0.001) as was te [blood glucose]/[C-peptide] ratio(21.9±14.6 vs. 139.2±43.8; P0.001). Discrminant analysis revealed a specificity of 96% to rule out the diagnosis of ‘insulinoma’ at a 1% probability threshold with a sensitivity of 100%. Conclusions We developed a new classification plot for the C-peptide suppression test in order to accurately identify those patients whose symptoms of hypoglycemia are not due to ndogenoushyperinsulinemia/insulinomas. Thus, the need for fasting tests and hospitalization costs can be reduced.
