Framework – Protein Biomarker Performance Improvement

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Often biomarker performance is focused on, and judged by, correlation with a specific condition, without sufficient regard for the specific assay used. However, there are three major factors related to assays that can also affect biomarker performance: method, selectivity, and biology. If they have not been fully investigated, then refocusing on them could lead to clinical performance of a biomarker.

Various factors affecting assay performance


  • Antibodies (epitopes)
  • Format, e.g., sandwich, competitive
  • Signal amplification
  • Dilution
  • Calibrators


  • Endogenous interferents, e.g., hemoglobin, lipids
  • Exogenous interferents, e.g., drugs
  • Cross reactivity
  • Matrix effects, e.g., plasma, serum, whole blood
  • Heterophilic antibodies
  • Autoantibodies


  • Normal inherent variability
  • Endogenous factors, e.g., age, gender
  • Exogenous factors, e.g., weight, smoking
  • Expression in other conditions
  • Different etiologies / somatic mutations
  • Isoforms, variants, and multimers

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