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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

Method

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

Selectivity

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

Biology

• 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