Purpose: We have previously shown that the total inflammatory load in transplant kidney biopsies (TxBx) can be determined with a high degree of accuracy using a standardized CD45 (leukocyte common antigen) immunohistochemical (IHC) assay in conjunction with whole slide digital imaging (WSI) and image analysis. The current study aims to assess the correlation between quantitative CD45 measurements and semiquantitative Banff (categorical) variables for total inflammation (ti) in TxBx with borderline changes (BL), and acute cellular rejection (ACR).

Methods: Consecutive TxBx with BL (n=17) and type 1 ACR (n=22) with no significant chronicity (ci0/ct0-1) were enrolled into the study. Six months protocol TxBx with normal morphology [(NL) n=13] served as controls. From each case, paired serial 3[micro]m-thick sections were stained for CD45 using standardized IHC. The average number of CD45 positive cell count/mm², as a measure of total inflammation (i.e., quantitative ti [qti]), was calculated for each biopsy. The qti values were statistically compared between NL, BL, and ACR cases and also between categorical Banff ti variables (ti0-ti3) using a t-test.

Results: The qti values were significantly higher in BL (947 ± SE 195) vs NL (332 ± SE 58) (p=.012) and in ACR (2322 ± SE 290) vs BL (947 ± SE 195) (p=.0007) cases with a linearity of R²= 0.40 between NL, BL, and ACR groups. While qti values were significantly different between cases with Banff ti0 (217 ± SE 89) and ti1 (591 ± SE 81) (p=.015), as well as ti2 (1063 ± SE 364) and ti3 (2400 ± SE 280) (p=.009) scores, there was no statistical difference in the qti values between cases with ti1 (591 ± SE 81) and ti2 (1063 ± SE 364) (p=.116) scores.

Conclusions: Objective quantitation of total inflammation (“qti”) with a standardized CD45 IHC assay combined with image analysis in TxBx reveals clear statistical separation of NL, BL, and type 1 ACR Banff diagnostic categories. However, the lack of statistical separation between Banff ti1 and ti2 scores indicates a potential weakness of Banff to reproducibly separate some of the BL cases from type 1ACR. Therefore, objective quantitation of inflammation may have a potential to improve the diagnostic accuracy and reproducibility of the pathologic diagnosis of ACR.

CITATION INFORMATION: Laszik L, Bowman S, Walavalkar V, Vincenti F, Laszik Z. A Quantitative CD45 Assay May Improve Diagnostic Accuracy of the Diagnosis of Acute Cellular Rejection in Transplant Kidney Biopsies. Am J Transplant. 2016;16 (suppl 3).

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