[Transthyretin amyloid cardiomyopathy. Features of histological diagnosis: study design].

AIM: To compare efficiency and specific features of transthyretin amyloid staining by different histological dyes and thus to assess their suitability for diagnostic purposes. MATERIALS AND METHODS: Samples of left and right heart ventricles were taken from patients over 70 years-old of both genders (n=10) with immunohistochemically verified transthyretin amyloidosis (ATTR). All samples were stained with Congo red, Alcian blue, toluidine blue and methylene violet. RESULTS: Specificity and sensitivity of Congo red staining was comparable to those of immunohistochemical staining. For verification of amyloid presence after Congo red staining one could use fluorescent microscopy instead of polarization microscopy. It allows a more accurate diagnosis of amyloidosis. Confocal microscopy with spectral unmixing improves detection sensitivity of amyloid by elimination of background fluorescence of muscle tissue and autofluorescence of lipofuscin. Alcian blue staining gives the same result as Congo red. In addition, its less labor-intensive and free of false-positive and false-negative results caused by final processing of slide preparation. Toluidine blue and methylene violet develop metachromatic staining upon binding to transthyretin fibrils, likely due to specific biochemical features of these fibrils. CONCLUSION: The most reliable method for histochemical diagnosis of ATTR is the Congo red staining with subsequent analysis using fluorescence or confocal microscopy. For diagnostic screening, the use of Sodium sulphate-Alcian blue staining method is highly promising. Metachromatic stains are less effective for ATTR diagnosis.

A Novel Method for Amyloid Detection in Human Tissue Load Using a Fluorescent Dye - Congo Red Analogue.

The aim of the study was to develop a new technology for the detection of amyloid in human tissues based on the fluorescent dye, disodium salt of 2,7-(1-amino-4-sulfo-2-naphthylazo)fluorene (DSNAF). MATERIALS AND METHODS: Synthesis of DSNAF was performed by diazotization of 2,7-diaminofluorene in a stream of argon followed by azo coupling with naphthionic acid. Identification of DSNAF was performed using MALDI mass spectrometry. Human myocardial samples from males and females aged from 85 to 98 years (n=11) were the material for the histochemical study. Myocardial paraffin sections were stained with a 0.1% aqueous solution of Congo red or with an aqueous solution (0.1 or 0.034%) of DSNAF under the same conditions. RESULTS: It has been demonstrated for the first time that a new fluorene-based analogue of Congo red, DSNAF, can be successfully used to identify amyloid deposits in histological sections of human myocardium. In terms of the specificity and intensity of amyloid staining, DSNAF is comparable to Congo red, which is the gold standard for detecting amyloid deposits. The fluorescence intensity of DSNAF when binding to amyloid fibrils is significantly higher than the intensity of Congo red fluorescence (with a lower intensity of background fluorescence of heart muscle tissue). This is especially useful for identifying small deposits of amyloid in the human tissues which is important when using small biopsies. CONCLUSION: The advantages of using DSNAF allow us to consider the developed technology for the detection of amyloid as a new promising method of identifying amyloid deposits in human tissues.