Quality improvement Initiative to eliminate silver precipitate during Periodic Acid Silver Methenamine Stain (PAMS) automated protocol of renal biopsies at McGill University Health Centre

Abstract

Abstract Introduction/Objective Annually, about 400 renal biopsies are processed at the McGill University Health Centre (MUHC) pathology laboratory located in Montreal, Canada. One of the stains used to visualize the glomerular basement membrane is Periodic Acid Silver Methenamine Stain (PAMS). In August 2020, a strong, granular precipitate of silver was noted during PAMS automated staining resulting in uninterpretable results and delay in the diagnosis. Based on a sample analysis, this problem affected 21 % of kidney biopsies. Methods/Case Report A cause-and-effect workflow was developed for systematic assessment of potential causes of the granular precipitate including pre-analytical and analytical factors. Some of the pre-analytical factors included length of time spent in transport before fixation and patient factors that predisposed precipitate formation. Analytical factors were categorized as fixation problems (temperature, pH, duration), embedding problems (parafilm temperature, cooling method, type of parafilm), slide preparation (temperature, water bath pH, dehydration and further processing steps), microtone parameters (microtone calibration, thickness, laboratory technologist expertise), automatic staining parameters (cartridge age, hematoxylin counterstain duration, wash-out period etc.) and coverslip placement (adhesive type, temperature, drying). Results (if a Case Study enter NA) Following our systematic approach, the cause of granular precipitate was identified as the timing of hematoxylin counterstain. A portion of renal biopsy tissue was taken from parafilm blocks of previouslly reported cases of patients with membranous glomerulonephritis to further test the hypothesis by introduction of various incubation times with the hematoxylin counterstain. Conclusion Best PAMS staining was attained when no hematoxylin counterstain was employed (instead, neutral red counterstain for 70 seconds was used). PAMS staining with hematoxylin counter stain for no more than 60 seconds was found to be acceptable for the interpretation of glomerular pathology.