Analytical evaluation and clinical application of insulin and C-peptide by a whole blood, lateral flow, point of care (POC) assay system

Abstract

The analytical performance and clinical application of measuring insulin and connecting peptide (C-peptide) by point of care (POC) assay were evaluated. A POC assay system (SelexOn, Osang Healthcare Inc., Anyang-si, Korea) was evaluated for precision, linearity, limit of blank (LOB), and limit of detection (LOD). Method comparison was performed with the Cobas Elecsys insulin and C-peptide assay (Roche Diagnostics GmbH, Mannheim, Germany) using 215 and 201 patient specimens for insulin and C-peptide, respectively. For clinical application, insulin resistance indices were studied. Homeostasis model assessment (HOMA) 1 and 2, Quantitative insulin sensitivity check index (QUIKI), fasting insulin resistance index (FIRI), and other indices were evaluated. The coefficient of variation (CV) of imprecision for low, medium, and high concentrations was 10.8%1, 15.99%, and 12.05%, respectively, for insulin and 9.21%, 13.51%, and 13.77%, respectively, for C-peptide. The linearity was validated to 839.78 pmol/L for insulin and to 17.30 nmol/L for C-peptide. LOB and LOD were 8.05 and 9.72 pmol/L for insulin and 0.05 and 0.08 nmol/L for C-peptide, respectively. For the method comparison, the regression equation was y = 1.259x − 8.818 (r = 0.957) for insulin and y = 1.163x – 0.088 (r = 0.985) for C-peptide. The ROC value and overall accuracy were as follows: HOMA2 (C-peptide), 0.809, 79.7%; TyG, 0.788, 73.6%; CPR, 0.775, 74.8%; HOMA1, 0.725, 70.3%; QUIKI, 0.720, 70.3%; FIRI, 0.715, 70.1%; McAuley, 0.658, 65.1%; HOMA2 (Insulin), 0.645, 64.7%; Raynaud, 0.611, 61.4%, respectively. The POC assay system for insulin and C-peptide provided reliable results through a rapid and simple test that could be applied to clinical settings.

Keywords:

• Insulin
• C-peptide
• diabetes mellitus
• point-of-care testing
• insulin resistance

Acknowledgements

The authors thank the Emergency Department and Laboratory Department staff for supporting this study. They thank Dr Jeongmin Lee (Department of Endocrinology, Seoul St. Mary's Hospital, Seoul, Korea) for giving generous advice related to this study. They thank Chankyu Kim, Se Woon Cho, and SangGil Bae for excellent technical assistance.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was supported by a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (Grant no. HI16C0821).