A final point about Calibration is to explain why it is important to avoid selecting strongly positive tissue controls (Figure 11). Strongly positive samples are terrible controls, very insensitive.
Figure 11. Avoid Selecting Strongly Positive Tissue Controls
- Strongly positive tissue controls can be misleading. If an assay is beginning to show drift, a control in the plateau range often will not show the change. A control in the dynamic range will have the sensitivity needed to show early changes in an assay.
- If you want to select two controls for an HER2 assay, select one control at the high end of the dynamic range and a second control at the middle of the dynamic range for optimal SPC reporting.