title: Icteric human samples: Icterus index and method of estimating an interference-free value for 16 biochemical analyses.
abstract: BACKGROUND
  Hemolysis, Icterus, and Lipemia constituting the HIL index, are the most common causes of interference with accurate measurement in biochemistry. This study focuses on bilirubin interference, aiming to identify the analyses impacted and proposing a way to predict nominal interference-free analyte concentrations, based on both analyte level and Icterus Index (Iict).
  
  
  METHODS
  Sixteen common analytes were studied: alanine aminotransferase (ALT), albumin (ALB), alkaline phosphatase (ALP), amylase (AMY), aspartate aminotransferase (AST), total cholesterol (CHOLT), creatinine (CREA, enzymatic method), fructosamine (FRUC), gamma-glutamyl transferase (GGT), HDL cholesterol (HDLc), total iron (Iron), lipase (LIP), inorganic phosphorus (Phos), total protein (PROT), triglycerides (TG), and uric acid (UA). Both the traditional 10% change in concentrations from baseline and the Total Change Level (TCL) were taken as acceptance limits. Nineteen pools of sera covering a wide range of values were tested on the Cobas® 6000 (Roche Diagnostics). Iictranged from 0 to 60.
  
  
  RESULTS
  Eight analytes increased (FRUC and Phos) or decreased (CHOLT, CREA, HDLc, PROT, TG, and UA) significantly when Iictincreased. FRUC, HDLc, PROT, and UA showed a linear relationship when Iictincreased. A non-linear relationship was found for TG, CREA, and for CHOLT; this also depended on analyte levels. Others were not impacted, even at high Iict.
  
  
  CONCLUSIONS
  A method of estimating an interference-free value for FRUC, HDLc, PROT, Phos, UA, TG, and CREA, and for CHOLT in cases of cholestasis, is proposed. Iictlevels are identified based on analytical performance goals, and equations to recalculate interference-free values are also proposed.
authors.affiliation: Faculté de Pharmacie, Aix Marseille Univ, APHM, Hôpital de la Conception, Service de Biochimie, UMR NORT INSERM 1062, INRA 1260, Marseille, France.
authors.forename: Alain
authors.identifier: http://orcid.org/0000-0002-4343-3426
authors.initials: A
authors.lastname: Nicolay
authors.affiliation: Faculté de Pharmacie, Aix Marseille Univ, APHM, Hôpital de la Conception, Service de Biochimie, Marseille, France.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Lorec
authors.affiliation: APHM, Hôpital de la Conception, Service de Biochimie, Marseille, France.
authors.forename: Guy
authors.initials: G
authors.lastname: Gomez
authors.affiliation: Faculté de Pharmacie, Aix Marseille Univ, APHM, Hôpital de la Conception, Service de Biochimie, Marseille, France.
authors.forename: Henri
authors.initials: H
authors.lastname: Portugal
mesh_terms: D001663:Bilirubin / Q000097:blood*; D015415:Biomarkers / Q000097:blood*; D001774:Blood Chemical Analysis / Q000592:standards*; D006461:Hemolysis; D006801:Humans; D006949:Hyperlipidemias; D007565:Jaundice / Q000097:blood*; D016014:Linear Models; D015203:Reproducibility of Results
chemical_list: D015415:Biomarkers; D001663:Bilirubin
keywords: bilirubin; biochemistry; correction; icterus index; interference