Observer variability in the assessment of type and dysplasia of colorectal adenomas, analyzed using kappa statistics

The aim of this study was to establish the intraobserver and interobserver variability in the assessment of histologic type (tubular, villous, and tubulovillous) and grade of cytologic dysplasia (mild, moderate, and severe) in colorectal adenomas.

One hundred eighty-seven slides of adenomas were assessed twice by three experienced pathologists, with an interval of two months. Results were analyzed using kappa statistics.

For agreement between first and second assessment (both type and grade of dysplasia), kappa values for the three specialists were 0.5345, 0.9022, and 0.4100, respectively. Agreement was better for type than for dysplasia. The strength of agreement was moderate for Observers A and C and almost perfect for Observer B. Agreement between all three observers was seen in 35.2 percent for both type and dysplasia in 61 percent for type and in 47.8 percent for dysplasia. The kappa values for Observer A vs. B and Observer C vs. B were 0.3480 and 0.3770, respectively (both type and dysplasia). Values for type were better than for dysplasia, but agreement was only fair to moderate.

The interobserver agreement was moderate to almost perfect, but the intraobserver agreement was only fair to moderate. A simpler classification system or a centralization of assessments would probably increase kappa values.