The impact of activity and chronicity scores on graft prognosis in renal allograft biopsies

Aim: The Banff classification is used to assess kidney allograft biopsies, and it is updated every two years based on data from the most recent research. Certain histological lesions in graft kidney biopsies are rated according to their severity and extent using the Banff classification. At the latest Banff 2019 conference, it has been discussed that the classification is complicated and subject to misunderstanding. Instead of the active/acute, chronic active, and chronic groups, which have been categorised separately for cellular and humoral rejection, which has been going on for years in the Banff classification, it has been proposed to report rejection type with activity and chronicity scores, similar to ISN/RPS Lupus nephritis classification. In this study, the presence and extent of histological lesions reflecting disease activity and chronicity, as well as the effectiveness and chronicity scores to be obtained, aimed to be investigated in relation with predicting graft loss. These features planned to be recorded during allograft indication biopsy in adult patients who have received living or cadaveric kidney transplants. Materials and methods: The study included 341 biopsies from adult recipients with renal allograft indication that were analyzed in the Ankara University Medical School, Department of Pathology between 2005 and 2021. Archival hematoxylin and eosin, PAS (periodic acid schiff), PASM (periodic acid methenamine silver), trichrome and immunohistochemically stained sections of C4d, CMV, and SV40 were reevaluated according to the most recent Banff classification by two pathologists (EÖ, SK). Lesions in the Banff elementary were graded for their size and severity. Activity and chronicity scores were determined using the method proposed by Haas et al. A seperate method proposed by Sethi et al. for use on native kidney biopsies was also used to determine an alternative chronicity score. Demographic information of the patients and clinical factors associated with prognosis were collected with the aid of hospital information system and patients' clinical follow-up charts. Correlation of activity and chronicity scores with graft prognosis, sensitivity and specificity values were analysed. Statistical analyses were performed using SPSS software ver.23.0 (IBM, Armonk, NY, USA), and p < 0.05 was accepted as statistically significant. Results: In our research, we observed no correlation between rejection type and graft loss or graft survival. Chronicity score-Haas, total biopsy score, and chronicity score-Sethi were significantly different between graft loss and non-loss groups. The activity score, on the other hand, demonstrated a borderline significant difference. The group with graft loss had higher creatinine (Cr) levels at the time of biopsy, lower eGFR levels, and a longer delay between transplantation and biopsy than the group without graft loss. Graft survival was negatively correlated with chronicity ratings and total biopsy scores. As chronicity scores and overall biopsy scores increase, the Cr value in the first year following a biopsy increases statistically significantly. The activity score is not correlated with graft survival and blood Cr value in the follow up year after taken biopsy. Conclusions: In our study, there was no correlation between rejection type and transplant outcome. Since the computation of the chronicity score and the overall biopsy score proposed by M. Haas et al. and S. Sethi et al. is related with graft survival, we believe it would be beneficial to include the activity and chronicity score alongside the diagnosis category in the biopsy report. With the Banff classification as a diagnostic classification method, we believe that the prognostic performance will improve, and additionally, changes in lesion scores progression or regression will be easier to track in repeated biopsies of patients. As a result, we anticipate that reporting of diagnostic category together with activity and chronicity scores will reduce variation among pathologists and facilitate consistency in the clinical management of patient follow-up and therapy.