Ethical approval
Ethical approval derives from the a priori approval granted by the Research Ethics Board of the Capital District Health Authority to the Division of Anatomical Pathology to use aggregate de-identified patient data for quality improvement purposes.
Setting
The Queen Elizabeth II Health Sciences Centre is a university-affiliated referral centre with an active renal transplant program that performs an average of 90 transplants per year. The anatomical pathology laboratory processes and reports approximately 200 native renal biopsies and 100 renal allograft biopsies per year, a number that has remained fairly stable over the last few years.
Participants
An analysis of adequacy for percutaneous renal biopsies performed at our centre was conducted using aggregate de-identified patient data. Biopsies performed at other centers and intraoperative biopsies were excluded from the analysis.
Interventions
The first intervention included:
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1.
Restriction of the performance of biopsies to a group of 11 radiologists from a group of approximately 20 radiologists with a subspecialty interest in this field of practice. No attempt was made to standardize biopsy technique among operators. All biopsies were performed with 16 gauge biopsy guns (C. R. Bard Inc., Murray Hill, New Jersey, USA) under real-time ultrasound guidance.
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2.
Provision of assessment of biopsy adequacy in every renal pathology report. Adequacy criteria for renal biopsies were locally defined through review of the literature, and discussion and consensus between the two renal pathologists who were practicing at the time that this was introduced. Two additional renal pathologists who participated in signing out renal biopsy reports during the course of the study also included the comment in their reports. It continues to be a standard statement in each renal biopsy report in our centre.
The second intervention was to have a medical laboratory technologist perform adequacy assessment on-site in the biopsy suite. The sample was examined under a dissecting microscope and the presence of glomeruli determined. If the sample was judged not to have glomeruli in any one of the cores for light, immunofluorescence or electron microscopy, then an additional core could be obtained. Three medical laboratory technologists were trained by pathologists assistants to identify glomeruli in renal biopsies examined under a dissecting microscope. The pathologists assistants had been trained previously by a renal pathologist. Any suboptimal or inadequate biopsies were discussed with the medical laboratory technologists after the renal biopsy report had been verified in an attempt to ascertain the reason why the particular renal biopsy was not adequate, such as a difficult procedure or patient factors.
Definition of adequacy
Native renal biopsies
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1.
Adequate biopsies contained at least ten glomeruli for light microscopy and at least one glomerulus each for immunofluorescence and electron microscopy.
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2.
Biopsies that did not meet these criteria but contained at least one glomerulus each for light, immunofluorescence and electron microscopy were classified as sub-optimal.
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3.
Biopsies that failed to meet the sub-optimal criteria were classified as inadequate.
Renal allograft biopsies
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1.
Adequate specimens contained ten or more glomeruli, two or more arteries, and at least one glomerulus each for immunofluorescence and electron microscopy.
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2.
Suboptimal specimens contained at least one glomerulus each for light, immunofluorescence and electron microscopy, and at least one artery, but did not meet the full adequacy criteria.
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3.
Allograft specimens that failed to meet the sub-optimal criteria were classified as inadequate.
Data analysis
The percentages of adequate, suboptimal and inadequate native renal and allograft biopsies were calculated for three periods:
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Period 1: Baseline, October 2005 to September 2006 (12 months). Adequacy was determined retrospectively by a renal pathologist reviewing the renal biopsy report and applying the numerical adequacy criteria.
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Period 2: After implementation of the first initiative, January 2007 to September 2011 (57 months). For renal biopsies from this period an adequacy statement was included in the renal biopsy report by the renal pathologist by applying the numerical adequacy criteria. Renal biopsy adequacy was monitored by auditing the adequacy statement in renal biopsy reports every three months.
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Period 3: After implementation of the second initiative, October 2011 to September 2012 (12 months). Adequacy was determined as for period 2 above.
The differences in adequacy between periods were expressed as the change in percentage of adequacy in the period in question compared to the preceding period, i.e. period 2 compared to period 1, and period 3 compared to period 2, with 95% exact confidence intervals. The Fisher’s exact test was applied to determine the statistical significance of the changes between periods. A two-tailed probability was used with an alpha level of 0.05 used to determine significance.
After analyzing our results, in order to evaluate the relationship between the interventions and the improvement in adequacy, we questioned whether potential improvement was contributed to by an increase in the number of passes taken with the biopsy gun during renal biopsy collection. Since the number of tissue cores submitted would approximate the number of passes, we examined a subset of the native renal biopsies comparing the number of cores recorded in the renal biopsy report with adequacy for three consecutive three month periods:
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Subset period 1: Prior to implementing the interventions, July, August and September, 2006
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Subset period 2: Between implementing the first and second sets of interventions, July, August and September, 2011
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Subset period 3: After implementing the second set of interventions, July, August and September, 2012
The Fisher’s exact test was applied to determine the statistical significance of the difference in proportions of biopsies with greater than three cores between adequate and suboptimal or inadequate biopsies in each subset period.
Statistical calculations were performed using SAS version 9.4 (Cary, North Carolina, USA).