In sequential multi-staining, how should chromogen be chosen and in what order?

• A. The most robust chromogens should be used; order: DAB, Fast Red, AEC (most to least robust).
• B. Weak chromogens first.
• C. Use only one chromogen.
• D. Order irrelevant.

Answer: (A)

In sequential multi-staining the processing steps can affect how well a chromogen remains visible as you probe additional antigens. Some chromogens are more resistant to the solvents, pH changes, and stripping steps than others. To keep earlier signals intact and clearly distinguishable through the full sequence, you stain in order from the most robust to the least robust. Among common options, DAB is the most stable, Fast Red is less so, and AEC is the least stable. Therefore, you’d apply DAB first, then Fast Red, and reserve AEC for the last round. This approach helps preserve earlier signals across rounds and keeps the final colors legible. Staining with a weak chromogen first can risk loss of that signal during later steps, using a single chromogen defeats multiplexing, and treating the order as irrelevant ignores how stability differences impact the final results.