Serrated Colon Polyps Are Not Diagnosed with a High Degree of Consistency in an Average Community Practice Setting: An Inter-Observer Agreement QA Study
LE Hamilton, SAC Medlicott, ZH Gao, SL Rasmussen, VG Falck. University of Calgary and Calgary Laboratory Services, Calgary, AB, Canada
Background: Sessile serrated adenoma(SSA) is a putative precursor of colorectal carcinoma and requires different clinical management than conventional hyperplastic polyp(HPP). While published studies show diagnostic agreement at Kappa levels of 0.41 - 0.83, it is our impression that there is significantly lower agreement in general practice due to inconsistent use of diagnostic criteria and terminology for SSA.
Design: We searched our 2007-06 database for 50 consecutive cases of HPP, SSA, and serrated adenoma(SA), and 35 cases of serrated polyp(SP). 50 normals were also included. Exclusion criteria were IBD and colonic adenoma/adenocarcinoma. Biopsy site, largest fragment size and age/gender of patient were noted. Three GI pathologists and a resident each did a blinded review of the 235 cases and assigned them to: normal, HPP, SSA, traditional serrated adenoma(TSA), mixed polyp(MX), adenoma(TA/VA) or other. A consensus diagnosis was achieved at multiheader microscopic review. For the study it was assumed that a diagnosis of SP equated to SSA, and SA to TSA. Unweighted Kappa statistics were used to compare levels of agreement.
Results: In 176 cases (original normals and others excluded), there was agreement between the original and consensus diagnosis in 95 cases (54%). There was 70% agreement for SSA and 52% for HPP. The SP cases were evenly split between HPP and SSA (46% each). The Kappa value for agreement between the four reviewers was 0.401(moderate); and between the original and consensus diagnosis was 0.352 (fair). The Kappa values for each reviewer were: 0.391, 0.672, 0.612, and 0.643. The diagnostic sensitivity for clinically significant lesions versus conventional HPP was 85%, and specificity was 44%.
|HPP (original dx)||26||13||0||0||3|
|SSA (original dx)||9||35||5||1||0|
|SP (original dx)||16||16||0||1||0|
|SA (original dx)||13||10||7||1||14|
Conclusions: A significant number of SSAs (18%) are undercalled as HPPs, and a large number of HPPs (58%) are overcalled as SSA/SP/SAs, resulting in potential inappropriate patient management. Even with the use of defined morphologic criteria, agreement is only moderate to good among reviewers. There is an urgent need for more accurate diagnostic modalities for SSA and prospective data about its clinical significance.
Wednesday, March 11, 2009 9:30 AM
Poster Session V # 77, Wednesday Morning