#856 Performance of ex vivo confocal microscopy in the assessment of Remuzzi score in preimplantation biopsies

Abstract

Abstract Background and Aims Confocal microscopy (CM) is a technique that generates digital images from fresh tissue samples with resolution comparable to that obtained with conventional stains. These images are digitally stained with Hematoxylin/Eosin-like. The clear advantage of this technique with respect to conventional staining is the speed in obtaining results which is of great importance in the donation process, as well as their digitalization. The aims of the present study were two: 1) to assess reproducibility for CM between two nephropathologist in preimplantation biopsies and 2) to describe the correlation between gold standard for preimplantation biopsies in our institution performed in frozen block and CM. Method Donor biopsies were reviewed according to Remuzzi score (RS) by on-call pathologist for frozen block and two nephropathologist for CM, blinded to the original frozen block report. The intraclass correlation coefficient (ICC) for every variable in RS was calculated for the two nephropathologists. Later, concordance between the techniques was evaluated by the κ index. Results We included 50 preimplantation biopsies between January and October 2023. Median donor age was 74 years (IQR 62-77.3), 56% were male, 74% had arterial hypertension and 24% had diabetes mellitus. Number of glomeruli were 23 (IQR 14.25-30.25). ICC was excellent for glomerulosclerosis (0.755) and total RS (0.787) and good for interstitial fibrosis (0.536), while fair for tubular atrophy (0.412) and poor for vascular narrowing (0.14). There was excellent agreement between frozen block and CM for interstitial fibrosis (κ 0.898) and global RS (κ 0.898) and substantial for glomerulosclerosis (κ 0.694) while it failed to moderate for vascular narrowing (κ 0.522) and fair for tubular atrophy (κ 0.37). Conclusion CM proved to have reproducibility between nephropathologists and comparability to our gold standard technique in evaluating preimplantation biopsies. The ease of acquisition of CM images suggests that it may be useful for rapid evaluation of graft histology.