Stokes' Congo Red
for Amyloid
Materials
- Mayer’s hemalum
- 80% ethanol
- Alkaline Congo Red
Material Amount Congo red as required Ethanol, 80% 100 mL Potassium hydroxide 0.2 g
Compounding Procedure
- Dissolve the potassium hydroxide in the ethanol.
- Add sufficient dye to saturate. Leave overnight and filter.
- Stable for about 3 months.
Tissue Sample
5µ paraffin sections of neutral buffered formalin fixed tissue are suitable. Other fixatives are likely to be satisfactory. Frozen sections are suitable.
Protocol
- Bring sections to water via xylene and ethanol.
- Place into alkaline congo red for 25 minutes.
- Wash with tap water for 5 minutes.
- Stain nuclei with Mayer’s hemalum for 5 minutes.
- Blue in running tap water for 10 minutes.
- Dehydrate rapidly in absolute ethanol.
- Clear with xylene and mount with a resinous medium.
Expected Results
- Amyloid – orange to red
- Nuclei – blue
- Background – colorless
Notes
- If congo red is applied for longer than 25 minutes, the background will show some coloration.
- Green birefringence is displayed under crossed polarizers.
Safety Note
Prior to handling any chemical, consult the Safety Data Sheet (SDS) for proper handling and safety precautions.
References
- Stokes, Gwen, (1976),
An improved congo red method for amyloid,
Medical Laboratory Sciences, v 33, 79
