title: Application of confocal laser scanning microscopy for the diagnosis of amyloidosis.
abstract: We analysed specificity and sensitivity of confocal laser microscopy (CLSM) on tissue sections for a diagnosis of amyloidosis, in an attempt to reduce technical errors and better standardise pathological diagnosis. We first set up a protocol for the use of CLSM on this type of specimen, using a group of 20 amyloid negative and 20 positive samples. Of all specimens, 2, 4 and 8-μm sections were cut. Sections were stained with Congo red (CR) and thioflavin-T (ThT) and observed by cross-polarised light microscopy (CR-PL), epifluorescence microscopy (CRF-epiFM and ThT-epiFM) and CLSM (CRF-CLSM and ThT-CLSM). To validate the method in a diagnostic setting, we examined tissue samples from 116 consecutive patients with clinical suspicion of amyloidosis, selected from the period 2005 to 2014 from the database of the Pathology Unit of the University of Padua. The results were compared with those of transmission electron microscopy (TEM), which we consider as reference. We found that with CRF-CLSM, the false negative rate was reduced from 17 to 5%, while the sensitivity of detection increased to 12%. The results were in complete agreement with those of TEM ThT-CLSM; both sensitivity and specificity were 100%. Finally, ThT-CLSM results did not vary with section thickness, and small amounts of amyloid could even be detected in 2-μm sections. In conclusion, we found ThT-CLSM to be more sensitive as a screening method for amyloidosis than CR and ThT epifluorescence optical imaging. The method was easier to standardise, provided images with better resolution and resulted in more consistent pathologist diagnoses.
authors.affiliation: Department of Cardiac, Thoracic and Vascular Sciences, University of Padua, Via Gabelli 61, 35100, Padova, Italy.
authors.forename: Chiara
authors.identifier: http://orcid.org/0000-0002-0275-4864
authors.initials: C
authors.lastname: Castellani
authors.affiliation: Department of Cardiac, Thoracic and Vascular Sciences, University of Padua, Via Gabelli 61, 35100, Padova, Italy.
authors.forename: Marny
authors.initials: M
authors.lastname: Fedrigo
authors.affiliation: Department of Cardiac, Thoracic and Vascular Sciences, University of Padua, Via Gabelli 61, 35100, Padova, Italy.
authors.forename: Anna Chiara
authors.initials: AC
authors.lastname: Frigo
authors.affiliation: Department of Cardiac, Thoracic and Vascular Sciences, University of Padua, Via Gabelli 61, 35100, Padova, Italy.
authors.forename: Mila Della
authors.initials: MD
authors.lastname: Barbera
authors.affiliation: Department of Cardiac, Thoracic and Vascular Sciences, University of Padua, Via Gabelli 61, 35100, Padova, Italy.
authors.forename: Gaetano
authors.initials: G
authors.lastname: Thiene
authors.affiliation: Department of Cardiac, Thoracic and Vascular Sciences, University of Padua, Via Gabelli 61, 35100, Padova, Italy.
authors.forename: Marialuisa
authors.initials: M
authors.lastname: Valente
authors.affiliation: Department of Clinical and Experimental Medicine, University of Padua, Padua, Italy.
authors.forename: Fausto
authors.initials: F
authors.lastname: Adami
authors.affiliation: Department of Cardiac, Thoracic and Vascular Sciences, University of Padua, Via Gabelli 61, 35100, Padova, Italy. annalisa.angelini@unipd.it.
authors.forename: Annalisa
authors.initials: A
authors.lastname: Angelini
mesh_terms: D000686:Amyloidosis / Q000175:diagnosis*; D004396:Coloring Agents; D003224:Congo Red; D005260:Female; D006801:Humans; D008297:Male; D018613:Microscopy, Confocal / Q000379:methods*; D046529:Microscopy, Electron, Transmission; D012680:Sensitivity and Specificity
chemical_list: D004396:Coloring Agents; D003224:Congo Red
keywords: Amyloid; Confocal laser microscopy; Congo red fluorescence; Histology; Thioflavin-T