<prompt> The most reliable investigation for amyloidosis isAbdominal fat pad aspirateUSGUrine examinationKidney biopsy  <response>: AmyloidosisA disease due to the accumulation of abnormal proteins which are formed due to abnormal protein misfolding. Light microscopy: Amorphous, eosinophilic, hyaline, extracellular substance that causes atrophy of adjacent cellsCongored stain: Pink or red color to amyloid depositsCongored under polarized microscopy: Apple green birefringenceTo differentiate primary amyloidosis from secondary amyloidosis: Treat with potassium permanganate and then perform congo red stain. Congo red stain shows positive in primary amyloidosis but negative in secondary amyloidosis due to potassium permanganate treatment. Primary-persists Electron microscopy: Continous non-branching fibril with a diameter of 7.5 to 10nmX-ray crystallography and Infrared spectroscopy- cross beta-pleated sheet conformationMost common organs involved: Kidney and Hea Most common test performed to diagnose amyloidosis: Abdominal fat pad aspirationMost reliable test performed to diagnose amyloidosis: Tissue biopsy Most rapid test to diagnose amyloidosis: Scintigraphy with radiolabelled serum amyloid O componentTest used in treatment follow up: Scintigraphy with radiolabelled serum amyloid O componentRef: Robbins 8e p249 