Addition of formaldehyde releaser imidazolidinyl urea and 2 MOPS buffer to urine samples enables delayed processing 3 for flow cytometric analysis of urinary cells 4 A simple , two step conservation method of urinary cells for flow cytometry 5 6

5 6 Paul Freund1,2*, Christopher M. Skopnik1,2, Diana Metzke1,2, Nina Goerlich1,2, Jan Klocke1,2, Emil 7 Grothgar1,2, Luka Prskalo1,2, Falk Hiepe2,3, Philipp Enghard1,2 8 9 1 Department of Nephrology and Medical Intensive Care, Charité Universitätsmedizin Berlin, 10 corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany 11 2 German Rheumatism Research Center Berlin (DRFZ), an Institute of the Leibniz Foundation, Berlin, 12 Germany 13 3 Department of Rheumatology and Clinical Immunology, Charité-Universitätsmedizin Berlin, Berlin, 14 Germany 15 16 * Corresponding author 17 E-mail: paul.freund@charite.de (PF) 18 . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 16, 2022. ; https://doi.org/10.1101/2022.04.07.22273579 doi: medRxiv preprint