title: Validation of an enzyme-linked immunosorbent assay for C-peptide analysis in Cameroon.
abstract: OBJECTIVE
  To validate an ELISA method for C-peptide analysis in Cameroon.
  
  
  METHODS
  We 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.
  
  
  RESULTS
  The 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 (R(2)=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.
  
  
  CONCLUSIONS
  This method is suitable for C-peptide analysis in low-income countries like Cameroon.
authors.affiliation: Diabetes Research Centre, Brussels Free University, B-1090 Brussels, Belgium.
authors.forename: M
authors.initials: M
authors.lastname: Asanghanwa
authors.forename: F
authors.initials: F
authors.lastname: van Genderen
authors.forename: K
authors.initials: K
authors.lastname: Verhaeghen
authors.forename: B
authors.initials: B
authors.lastname: Van der Auwera
authors.forename: E
authors.initials: E
authors.lastname: Sobngwi
authors.forename: J C
authors.initials: JC
authors.lastname: Mbanya
authors.forename: C
authors.initials: C
authors.lastname: van Schravendijk
mesh_terms: D002096:C-Peptide / Q000097:blood*; D002163:Cameroon; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D057230:Limit of Detection; D008297:Male; D008422:Materials Testing; D011204:Poverty Areas; D055550:Protein Stability; D012016:Reference Values; D015203:Reproducibility of Results
chemical_list: D002096:C-Peptide