Validation of an enzyme-linked immunosorbent assay for C-peptide analysis in Cameroon

AimsTo validate an ELISA method for C-peptide analysis in Cameroon.MethodsWe evaluated the linearity, detection limit, functional sensitivity, precision and accuracy, and further investigated for cross-reactivity by proinsulin, and interferences by lipids, bilirubin and hemoglobin. This method was compared with the Roche electrochemiluminescence immunoassay. C-peptide stability was assessed following a series of freeze–thaw cycles, and after storage at room temperature. The C-peptide reference range was determined by analyzing fifty plasma samples of Cameroonians without diabetes.ResultsThe ELISA was linear at least up to 7.09 μg/L, and had a detection limit of 0.09 μg/L, and a functional sensitivity of 0.32 μg/L. The inter- and intraassay %CV were 2.9–9.9%, and 5.2–9.4%, respectively. Recoveries were 81–94% in serum, and 93–98% in buffer. Comparison with the ECLIA yielded a good correlation coefficient (R2 = 0.98). There was no cross-reactivity with proinsulin, and no interference with lipids, bilirubin and hemoglobin. C-peptide was stable at room temperature for 24 h and up to 7 freeze–thaw cycles for medium (1–6 μg/L) and high (>6 μg/L) levels (<−15 °C and <−70 °C). The reference range for C-peptide was 0.38–3.63 μg/L.ConclusionsThis method is suitable for C-peptide analysis in low-income countries like Cameroon.