Table 2 Comparison of bioanalytical assays with immune response-based assays

Number of analytes

Single analyte relative to biological functions (small molecules or macromolecules)

Multiple analytes with complex functional relationships between tumor and immune system

Category of measurement

Absolute quantitation

Quasi-quantitative, relative-quantitative or qualitative. Qantification is available for specific assays

Reference material

Available

Not available, limited availability or available - depends on the assay

Linearity of analyte(s)

Known

Unknown or do not demonstrate linearity, often unknown dynamic ranges, or dynamic range can be established-depends on the assay

Limit of detection (LOD)

Available

Not quantifiable or LOD available - depends on the assay

Sample processing

Extraction required for small molecules; Direct measurement in biological matrix without sample pretreatment

Single cells or specific cell types frequently required for blood-based assay; tissue processing required for FFPE samples; tissue processing required for DNA and RNA

Function assessment

Not necessary - a determinant of the static molecular status

Functional assays often require ex vivo response to stimuli

Time for archived clinical samples analysis

Relatively short, <1 yr

Often long >1 yr; Depends on the stability of biomarker/assay