Knowledge Base › Troubleshooting Atlas › Special stains
Congo red weak or no apple-green birefringence
What it looks like
Congo red-stained sections show weak or absent apple-green birefringence under polarized light. The expected bright green appearance is diminished or missing.
Where it usually appears: Typically observed in cases of amyloidosis or in tissues where amyloid deposits are suspected.
Likely causes
- Insufficient staining time
- Inadequate reagent quality
- Improper slide preparation
- Incompatible mounting medium
- Incorrect polarized light settings
Immediate checks
- Verify reagent expiration date
- Check staining protocol timing
- Inspect slide for proper thickness
Corrective action
- Repeat staining with fresh reagent
- Ensure thorough tissue fixation
- Adjust polarization settings
Preventive action
- Regularly calibrate polarizing microscope
- Maintain proper storage of reagents
- Follow SOP for staining procedures meticulously
This atlas is for educational purposes for laboratory professionals. It does not replace your institutional SOPs, manufacturer instructions, validated protocols or pathologist judgment. Adapt any action to your laboratory and equipment.
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