TABLE 2.
Comparison of Different Methods of Assessing Immunohistochemical Stain Results
| Visual Assessment of Control Tissue (Current Method Used by All Laboratories) | Digital Image Analysis of Control Tissue | Control Microbeads (High and Low Levels) | Calibrator Microbeads | |
|---|---|---|---|---|
| Summary of workflow | Identify appropriate cases from archives | Identify appropriate cases from archives | Purchase microbead controls | Purchase calibrator slides |
| Locate and pull blocks | Locate and pull blocks | Manually pipette controls instead of mounting tissue controls | Process calibrators on immunostainer | |
| Block cutting | Block cutting | Process slides with patient samples on immunostainer | Evaluate calibrators visually or with digital image analysis (currently performed by the vendor) | |
| Stain slides | Stain slides | Stained slides reviewed by pathologist | ||
| Stained slides reviewed by pathologist | Whole slide images | |||
| Digital image analysis (quantification of stain intensity) | ||||
| Analyte concentration known? | No | No | Yes | Yes |
| Current uses | Detect gross assay problems or instrument failure | None | Detect gross assay problems or instrument failure) | Used to establish limit of detection |
| Potential future uses | Same as above | Fine discrimination of partial IHC assay problems | Routine demonstration that the correct IHC stain was performed and was performed with satisfactory results (expected intensity) | Determine LOD for ensuring interinstitutional alignment of assay performance |
| Levey-Jennings analysis | With added programs for image analysis and routine quantitation, global comparisons within runs, between runs, and between instruments to identify subtle changes in IHC stain performance that may be go unnoticed by visual assessment | |||
| Degree of quantitation of intensity | Limited, typical scale is to 0 to 3+ | Precise but relative quantification | Precise but relative quantification | Intensity quantification used for calculating LOD and dynamic range |
| Sensitivity to detect subtle decrements and variability in stain intensity | Lowest | Moderate | Low if visually assessed | Highest |
| Moderate if with digital image analysis | ||||
| Assess limit of detection? | No | No | No | Yes |
| Currently available for routine use | Yes | No (requires custom workflow) | Dependent on availability from vendor | Dependent on availability from vendor |
IHC indicates immunohistochemistry; LOD, limit of detection.