Digitally reinforced polarization of hematoxylin-eosin in the diagnosis of renal amyloidosis.

Systemic amyloidosis is a rare disorder, characterized by extracellular accumulation of Congo red positive fibrillar amyloid protein deposits that have an amorphous, eosinophilic appearance on hematoxylin-eosin stained preparations. The kidney is the most commonly affected organ by systemic amyloidosis. Congo red staining increases the positive birefringence of the weakly birefringent unstained amyloid. In this study, we investigated the potential diagnostic power of digitally reinforced birefringence of routine hematoxylin-eosin stained slides from renal biopsies. We reviewed 130 hematoxylin-eosin stained slides for polarization. Sixty-five new amyloidosis cases were diagnosed by renal biopsy. All renal biopsies were evaluated by light microscopy and immunofluorescence. Slides were reevaluated blindly using a microscope (Olympus BX51) that was attached polarization filters and connected to a digital camera (Olympus DP21, SAL). Deposits that showed green birefringence on hematoxylin-eosin preparations with digitalized microscopy were considered positive and the results were confirmed using Congo red. Of the 65 Congo red confirmed amyloid positive biopsies, 61 showed green birefringence with hematoxylin-eosin. Of the 65 Congo-red confirmed amyloid negative biopsies, two were considered to be false positive. The sensitivity, specificity, and positive and negative predictive values were estimated as 94%, 97%, 97% and 94% respectively. We concluded that polarized hematoxylin-eosin sections can be used digitally as a fast and first step diagnostic method for renal amyloidosis.