Table 2.
Comparison of bioanalytical assays with immune response-based assays
| Characteristics | Bio-analytical Assays | Immune-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 |
Source: Guidance for Industry: Bioanalytical Method Validation [178]