Quantitative evaluation of interstitial fibrosis with Sirius Red in IgA nephritis

Computer-assisted evaluation enhances the quantification of interstitial fibrosis in renal implantation biopsies, measures differences between frozen and paraffin sections, and predicts delayed graft function

Background

(Pre-)Implantation biopsies provide important data on the quality of donor kidneys. Interstitial fibrosis, as a known predictor for kidney disease progression, is an essential feature of this evaluation. However, the assessment of frozen sections of implantation biopsies is challenging and can result in the disposal of candidate organs. We sought to apply digital image analysis (DIA) to quantify the differences between frozen and paraffin sections when evaluating interstitial fibrosis, identify factors that influence these variations and test the predictive value of the computerised measures.

Methods

We quantified the differences between frozen and paraffin sections in the same biopsy samples by measuring Sirius red-stained interstitial areas (SRIA) in DIA. We compared them to the original reports, and retrospectively correlated our findings to clinical data, graft function and outcome in 73 patients.

Results

Frozen sections display a broader interstitial area than paraffin sections, in some cases up to one-third more (mean difference + 7.8%, range − 7 to 29%). No donor-related factors (age or gender, cold ischemia time, or non-heart-beating donor) influenced significantly this difference. Compared to the original assessment of frozen vs paraffin sections in optical microscopy, the DIA of interstitial fibrosis shows a higher consistency (ICC 0.69). Our approach further allows to distinguish SRIA in paraffin sections as an independent predictor for delayed graft function (OR = 1.1; p = 0.028).

Conclusions

DIA is superior to and more consistent than routine optic microscopy for interstitial fibrosis evaluation. This method could improve implantation biopsy diagnostics and help to reduce disposal of organs.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40620-022-01315-y.

Usefulness of morphometric image analysis with Sirius Red to assess interstitial fibrosis after renal transplantation from uncontrolled circulatory death donors

Early interstitial fibrosis (IF) correlates with long-term renal graft dysfunction, highlighting the need for accurate quantification of IF. However, the currently used Banff classification exhibits some limitations. The aim of our study was to precisely describe the progression of IF after renal transplantation using a new morphometric image analysis method relying of Sirius Red staining. The morphometric analysis we developed showed high inter-observer and intra-observer reproducibility, with ICC [95% IC] of respectively 0.75 [0.67–0.81] (n = 151) and 0.88 [0.72–0.95] (n = 21). We used this method to assess IF (mIF) during the first year after the kidney transplantation from 66 uncontrolled donors after circulatory death (uDCD). Both mIF and interstitial fibrosis (ci) according to the Banff classification significantly increased the first three months after transplantation. From M3 to M12, mIF significantly increased whereas Banff classification failed to highlight increase of ci. Moreover, mIF at M12 (p = 0.005) correlated with mean time to graft function recovery and was significantly associated with increase of creatininemia at M12 and at last follow-up. To conclude, the new morphometric image analysis method we developed, using a routine and cheap staining, may provide valuable tool to assess IF and thus to evaluate new sources of grafts.