Clinical and Laboratory Evaluation of a New Specific Point-of-Care Test for Intact Proinsulin.

BACKGROUND: Intact proinsulin is a biomarker for pancreatic ß-cell dysfunction. In large prospective studies in nondiabetic subjects, elevated intact proinsulin predicted development of type 2 diabetes and/or macrovascular events up to 7 years in advance. This study was performed to evaluate a new semiquantitative lateral flow-based point-of-care rapid test (POCT) for elevated intact proinsulin (cutoff: 15 pmol/L). The test requires 10 µL of capillary whole blood, with visual readout after 5 minutes. It is best applied at 2 hours after a glucose challenge or a meal.

METHODS: POCT results were obtained by health care professionals from 60 patients and healthy subject (33 female, 27 male, 28 type 2 diabetes, age: 53.6 ± 12.3 years). An additional venous blood sample was obtained from all participants for measurement of intact proinsulin by means of a quantitative ELISA reference method (TecoMedical, Sissach, Switzerland).

RESULTS: Elevated intact proinsulin levels (>15 pmol/L) were determined by the reference method in 26 participants, of whom 22 were also positive with the POCT (sensitivity: 85%). All 34 subjects with low intact proinsulin levels were tested negative by the POCT (specificity: 100%).

CONCLUSIONS: The test successfully detected elevated postprandial intact proinsulin levels in 85% of the tested subjects and no false positive test result occurred. This POCT can therefore serve as a simple screening tool for identification of patients with prevalent ß-cell dysfunction, who are at high risk for development of type 2 diabetes and/or macrovascular events within the next 5-7 years.