Aim: To investigate the efficacy of the digitally reinforced hematoxylin-eosin polarization (DRHEP) technique for detection of amyloidosis in rectal biopsies.
Methods: One hundred hematoxylin-eosin (HE) stained rectal biopsies with Congo-red (CR)-positive amyloid depositions and 50 control cases with CR-negative amyloid-mimicking areas were scanned blinded to the CR results for amyloid depositions under both bright and polarized light, and digitally photographed using the DRHEP technique, to accentuate the faint birefringence observed in HE slides under polarization. The results of DRHEP and HE evaluation were statistically correlated with CR polarization results with respect to presence and localization of amyloid deposits as well as amyloid types.
Results: Amyloid deposits showed yellowish-green birefringence by DRHEP, which allowed identification of amyloidosis in 41 HE-unsuspected cases (P = 0.016), 31 of which only had vascular deposits. True positivity was higher, and false negativity and positivity were lower by DRHEP, compared to evaluation by HE (69%, 31%, and 0.8% vs 33%, 67%, and 33%, respectively; P < 0.0001). The sensitivity, specificity, accuracy, and positive and negative predictive values for DRHEP were 69%, 98%, 78.6%, 98.5%, and 61.25%, respectively. Reasons for DRHEP false negativity were presence of extensive background birefringence in 12 cases, absence of CR birefringent vessel in 3 cases, and missing of the tiny deposits in 9 cases, which could be improved by experience, especially in the latter case. No correlation was found between age, gender, sites of deposits, or amyloid types.
Conclusion: The DRHEP technique improves diagnostic accuracy when used as an adjunct or a prior step to CR staining, especially for cases with limited tissues for further analysis.
Keywords: Amyloidosis; Congo red; Hematoxylin-eosin; Microscopy; Polarization; Rectum.