title: A chromogranin A ELISA absent of an apparent high-dose hook effect observed in other chromogranin A ELISAs.
abstract: BACKGROUND
  Routine testing for chromogranin A (CgA) using an established commercial ELISA revealed an apparent high-dose hook effect in approximately 15% of specimens. Investigations found the same effect in two additional ELISAs. We hypothesized that a CgA derived peptide(s) at high concentrations was responsible but experiments were inconclusive. Here we describe the analytical performance characteristics of the Chromoa™ CgA ELISA that did not display the apparent high-dose hook effect.
  
  
  METHODS
  Performance characteristics of the Chromoa ELISA were assessed. The reference interval was established utilizing healthy volunteers. Specimens producing the apparent high-dose hook effect in other assays were evaluated using the Chromoa ELISA.
  
  
  RESULTS
  The limit of detection was 8ng/ml. Linearity was acceptable (slope=1.04, intercept=18.1 and r(2)=0.997). CVs were ≤4.6 and ≤9.3% for repeatability and within-laboratory imprecision, respectively. CgA was stable at ambient and refrigerated temperatures for a minimum of two and 14days, respectively. An upper reference interval limit of 95ng/ml was established. Specimens demonstrating the apparent high-dose hook effect in other ELISAs did not exhibit the phenomenon using the Chromoa ELISA.
  
  
  CONCLUSIONS
  The Chromoa ELISA demonstrates acceptable performance for quantifying serum CgA. The apparent high-dose hook effect exhibited in other ELISAs was absent using the Chromoa assay.
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT, United States.
authors.forename: J Alan
authors.initials: JA
authors.lastname: Erickson
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT, United States; Department of Pathology, University of Utah Health Sciences Center, Salt Lake City, UT, United States. Electronic address: david.grenache@path.utah.edu.
authors.forename: David G
authors.initials: DG
authors.lastname: Grenache
mesh_terms: D000328:Adult; D053379:Chromogranin A / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D057230:Limit of Detection; D008297:Male; D008875:Middle Aged; D055815:Young Adult
chemical_list: D053379:Chromogranin A
keywords: Chromogranin A; ELISA; High-dose hook effect