Brouwer, W.L. de (2016) The impact of different polyp size measurement methods: Endoscopist versus pathologist : An analysis of of the causes and differences between two polyp size measurements (endoscopist versus pathologist), the causes of the differences and the impact on col. thesis, Medicine.
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Abstract
Introduction: Early detection and removal of colonic adenomas reduces colorectal cancer (CRC) incidence. After adenoma removal, surveillance is often recommended. The Dutch Guideline on Colorectal Polyp Surveillance uses an index to determine surveillance interval, based on the number of adenomas, adenoma size > 9 mm, villous histology and adenoma location proximal to the splenic flexure. Regarding adenoma size, the guideline does not state how this should be measured (although the guideline is based on a study of endoscopic bedside (E)-measurements). Confusion has been arisen because the specimen size as measured on arrival at the pathology department (P-measurement) is sometimes different. Recently the national screening program on CRC recommended the largest value (L) of Eand P should be used. We investigated the agreement between both measuring methods and whether pathology measurements generate - on average - smaller sizes, as many believe that formalin fixation causes shrinkage. We also investigate whether flat polyps were more susceptible to E-P differences and the influence of the endoscopist. Secondary, we assessed the impact of E, P and L on surveillance recommendations and number of surveillance colonoscopies. Material and methods: This was a single-center, retrospective study. All colonoscopies between January 2015 and June 2015 were analysed. Fragmented resections were excluded. For each polyp, the difference (Δ) between E- and P-measurements was calculated (Δ=E-P). As Δ was normally distributed, the 0-hypothesis (average Δ does not significantly differ from 0) was tested using a paired t-test. We (arbitrarily) defined a level of agreement by using the absolute value of Δ (|Δ|) as: excellent: |Δ| ≤ 1 mm; fair: |Δ| = 2 mm; moderate: |Δ| = 3 or 4 mm; and poor: |Δ| > 4 mm. The Intraclass Correlation Coefficient (ICC) was used to quantify the agreement. We used univariate multiple regression analysis to assess which variables had independent influence on Δ. Finally, we calculated the impact on surveillance interval for use of either measurement. For this purpose, patients with overruling reasons for surveillance, e.g. Lynch syndrome, potentially incomplete resections, were also excluded. Results: Between January and June 2015, 1281 consecutive colonoscopies were analysed, in 509 of them (33%) 1439 polyps had been removed. After exclusion of fragmented lesions and overruling reasons for surveillance, 380 colonoscopies and 945 polyps were analysed. Median P- and E-measurements were 5 mm. Mean Δ was -0.43 (SD 2.48, p < 0.001), implicating on average larger P-measurements: Indeed, 45.1% of P-measurements were larger than the Emeasurements; in 32.6% they were smaller. In 56.7% of cases |Δ| was rated as “excellent”, only in 22.3% |Δ| was rated as “moderate” or “poor”. The ICC resulted in a single measures value of 0.876, which also implicates good agreement. Multiple regression analysis revealed that the endoscopist was the only independent factor associated with Δ (p < 0.0005). Especially polyp morphology was not an independent determinant (p = 0.30). Indeed, some endoscopists structurally overestimated or underestimated polyp size. Of the 380 patients, 339 would have surveillance based on E-measurements (88 at 3-years, 251 at 5 years) and 342 on P-measurements (92 at 3 years, 250 at 5 years) and 344 on L-measurement (96 at 3 years, 248 at 5 years). A change in surveillance recommendation occurred in 4.5% when using Pmeasurement and 2.9 % using L-measurement with an average increase in the yearly burden of colonoscopies of 1.4% using P-measurement and 2.6% using L-measurement. Conclusion: We found no evidence that formalin causes sample shrinkage or that flat polyps are rated smaller by the pathologist due to curling. The main determinant of measurement differences was the endoscopist. Although E-P agreement was generally good and the overall impact on surveillance interval might be perceived as small, E-P differences resulted in a substantial absolute increase of colonoscopy burden on a population level. Given the limited availability of colonoscopy resources, we strongly plea for a more objective endoscopic measurement of polyp size, for instance by using a ruler.
| Item Type: | Thesis (Thesis) |
|---|---|
| Supervisor name: | Faculty supervisor: and Borg, Dr. F. ter MD PhD gastroenterologist and Deventer Hospital, Department of gastroenterology |
| Faculty: | Medical Sciences |
| Date Deposited: | 25 Jun 2020 10:54 |
| Last Modified: | 25 Jun 2020 10:54 |
| URI: | https://umcg.studenttheses.ub.rug.nl/id/eprint/1501 |
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