#2795 PROSPECTIVE ASSESSMENT OF THE NEED FOR AND ADDED VALUE OF MOLECULAR DIAGNOSTICS OF KIDNEY ALLOGRAFT BIOPSIES: AN EVALUATION IN CLINICAL PRACTICE

Abstract

Abstract Background and Aims The Molecular Microscope Diagnostic System (MMDx) may resolve inconclusive histology findings, as preserved biopsy material can be examined after histology findings have been obtained. The extent to which this proposed approach can be implemented in clinical practice remains an open question. Method We prospectively analyzed 104 consecutive indication kidney allograft biopsies by histology and molecular diagnostics at the University Hospital Zurich from April 2022 to December 2022. Pathologists and clinicians with experience in molecular diagnostics assessed the need for MMDx by questionnaire when the histology report was available. Clinicians then assessed the added value of the molecular diagnostics by questionnaire when the MMDx report was available. Results 29 of 104 cases (28%) showed rejection by histology, 42 of 104 cases (40%) showed no rejection by histology, and 33 of 104 cases (32%) showed histologic findings insufficient to diagnose ABMR due to an absence of diagnostic criteria groups 2 and/or 3. Pathologists considered molecular diagnostics indicated in 42 of 104 cases (40%), 9 cases to give extra confidence, and 33 cases for diagnostic clarification concerning rejection. Clinicians considered molecular diagnostics indicated in 54 of 104 (52%) cases, 5 cases to give extra confidence, and 49 for diagnostic clarification concerning rejection. In 33 cases with histologic findings insufficient to diagnose ABMR, molecular diagnostics were considered indicated by pathologists and clinicians. Molecular diagnostics allowed the diagnosis of ABMR in 8 of 33 cases (24%). In addition, 11 of 104 cases (11%) showed a discrepancy between the histologic findings and the molecular diagnosis. Clinicians considered adjustment of treatment based on the MMDx report in 3 of 11 discrepant cases. Pathologists and clinicians considered molecular diagnostics indicated in 2 of 11 and 3 of 11 discrepant cases, respectively. Conclusion The need for molecular diagnostics goes beyond the recommendation of the 2018 Banff classification for histologic findings insufficient to diagnose ABMR. However, the added value of molecular diagnostics appears to be largely limited to these cases.