Which statement describes the Warthin-Starry stain in this context?

• A. Calibration uses an acidic solution
• B. NBF requires acidic
• C. NBF uses alkaline
• D. Water is used

Answer: (A)

Warthin-Starry is a silver-impregnation stain used to visualize certain organisms in tissue, and its outcome hinges on the chemical environment during the staining and development steps. The key point here is that an acidic calibration step is required to drive the silver reduction properly, producing the visible deposits on the target organisms while limiting background staining. This acidic condition controls the reaction, making the stain specific and reproducible.

Fixatives like neutral buffered formalin are about preserving tissue before staining, not about how the silver reaction occurs in this stain. Water is used in many steps, but it doesn’t define the essential chemistry of this stain. So, describing calibration with an acidic solution captures the critical requirement for Warthin-Starry staining.