Laboratory Diagnosis Of Amyloidosis

Laboratory Diagnosis Of Amyloidosis

Write a note on laboratory diagnosis of amyloidosis.
Answer:

Laboratory Diagnosis Of Amyloidosis

• Biopsy examination: Histologic examination of biopsy material is the commonest and confirmatory method for diagnosis in a suspected case of amyloidosis. Biopsy of an obviously affected organ is likely to offer the best results, For Example. kidney biopsy in a case on dialysis, sural nerve biopsy in familial polyneuropathy. The affected organ reveals deposits of amyloid in the walls of blood vessels.
• In vivo Congo red test: A known quantity of Congo red dye may be injected intravenously into a living patient. If amyloidosis is present, the dye gets bound to amyloid deposits and its levels in the blood rapidly decline. The test is, however, not popular due to the risk of anaphylaxis to the injected dye.
• Other tests: A few other tests which are not diagnostic but are supportive of amyloid disease are protein electrophoresis, immunoelectrophoresis of urine and serum, and bone marrow aspiration.

Laboratory diagnosis of amyloidosis

• Special stains used to demonstrate amyloidosis
  • H&E stain: Amyloid by light microscopy with H and E stain appears as extracellular, structure, and eosinophilic hyaline material. It appears pink in color.
  • Metachromatic stains: The metachromatic stains are methyl violet/crystal violet which imparts rose pink color to amyloid deposit.
  • Congo red stain: Underlightmicroscopywhilestaining the amyloid with Congo red stain it gives pink red color. In polarizing light, it provides red-green birefringence.
  • Thioflavin­T and S: Under this amyloid emits secondary fluoresces yellow color.
• Immunohistochemistry: Various antibody stains against specific antigenic protein types of amyloid are available. The most common antibodies are anti-AA, anti-lambda, and anti-kappa antibodies to differentiate between different types of amyloids.
• Non­specifi stains:
  • Standard Toluidine Blue: It gives orthochromatic blue color to amyloid which under polarizing microscopy produces dark red birefringence.
  • Alcian blue: Impart blue-green color and is used for mucopolysaccharide content in amyloid.
  • Periodic Schifftain (PAS): Used for demonstration of carbohydrate content. It appears pink in color.