18 Months Is a Reliable Period for Storing Immunofluorescent (IF) Slides of Renal Biopsies for Review in Room Temperature (70 0F)

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American Journal of Clinical Pathology


Immunofluorescent (IF) slides are ideally kept for later internal and external reviews in addition to available slides for light microscopy (LM) and electron microscopy (EM). But there is no standard for how long the IF slides should be kept, yet the maintenance of IF staining intensity over time is a major concern. In this quality control study, we determined whether IF staining intensity was reduced in renal biopsies over 5 years. We retrospectively queried our database for control cases composed of 21 focal segmental glomerulosclerosis (FSGS) and 35 study cases with immune complex mediated glomerulopathy (ICMG, including membranous glomerulopathy, lupus nephritis, and post-infectious glomerulonephritis and membranoproliferative glomerulonephritis), from January 2009 to June 2010. The IF slides were kept in dark boxes at lab room temperature (70°F) after the initial evaluation for diagnosis. IF slides for IgG, kappa, and lambda were first reviewed for fluorescent intensity after a storage time ranging from 1 to 17.5 months (m) in September 2010. The second review was performed 40 months later. The fluorescent intensity was scored from 0 to 3+. The re-examined scores were compared with initial scores statistically. All control cases (FSGS) essentially showed no staining in both initial and re-examination. In the ICMG group, there was small but nonsignificant reduction in staining intensity for IgG, kappa, and lambda over time during the first review (up to 10% reduction in overall staining intensity). Overall, there was significant correlation between initial scores and first re-examination scores. The second review showed up to 66% reduction of overall staining intensity for IgG, kappa, and lambda in ICMG cases. Our data suggest that IF staining intensity in ICMG can be adequately maintained around 18 months; thus we recommend each renal pathology keeps renal IF slides in a dark box at room temperature (70°F) for at least this length of time.





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