Sa1012 Volume of case reporting is an important determinant of serrated polyp subtype diagnoses by pathologists in a national bowel cancer screening programme

Introduction Definitions around serrated colorectal polyps have evolved, with more awareness of their premalignant potential. Differentiating the often subtle morphological differences between the premalignant sessile serrated lesion (SSL) from the benign hyperplastic polyp (HP) in serrated colorectal pathology remains a challenge. This study aimed to investigate trends in pathologist reporting of overall and individual serrated polyp subtypes from the first ten years of the Northern Ireland (NI) Bowel Cancer Screening Programme (BCSP),
comparing reporting patterns from pathologists reporting high and low volumes of such cases.
Methods The NI BCSP commenced in 2010 and was fully implemented across the
NI population (1.9 million) by 2012. Since inception of the programme, histopathology details relating to all specimens have been recorded within a dedicated BCSP database. Comparisons of diagnoses between high volume pathologists (defined as those who reported at least 100 BCS cases per year active within the programme) and low volume pathologists (defined as reporting between 10-99 BCS cases per year active within the programme) were
investigated up to end 2020. The NI BCSP utilised faecal occult blood (FOB) test screening during this timeframe. Cases missing a valid pathologist identifier were excluded from the analysis (representing 3.5% of diagnoses in the BCSP). Results Over the first 11 years of the BCSP, eight pathologists were classified as high volume and 15 pathologists were classified as low volume. High volume pathologists reported 22,124 specimens compared with 8,794 specimens reported by low volume pathologists (71.4% and 28.4% of total specimens,
respectively). Overall, serrated polyp diagnosis patterns were relatively stable, representing 18% of all diagnoses in the NI BCSP in Years 1-11. However, differences were observed between serrated polyp subtypes reported amongst high and low volume pathologists. Within the high volume pathologists, the proportion of diagnoses reported as SSLs increased from 1% to 10% of all BCSP specimens reported by this group from Years 1-11, while the proportion of specimens reported as HP declined from 18% to 8%. Within the low volume
pathologists, the proportion of specimens reported as SSLs only rose from 2% to 6%, while HP reporting declined from 15% to 10% of specimens reported by this group over the same timeframe. Conclusion Diagnosis of premalignant SSLs has increased over the past decade by all pathologists, but low volume pathologists continue to report proportionally fewer premalignant SSLs than high volume reporting pathologists.