Interrater agreement and reliability of the Bosniak classification for cystic renal masses version 2019.

Background: The Bosniak classification for cystic renal masses has undergone refinements since its inception. The 2019 version provides more objective criteria to enhance interrater agreement but needs validation. This study compares the interrater agreement of the 2005 and 2019 Bosniak classifications for cystic renal masses.

Methods: Forty cystic renal masses identified on computed tomography scans were selected, distributed equally among the five classes of the 2005 Bosniak classification. Eight radiology residents participated in 2 consecutive rating sessions using the 2005 and 2019 versions, respectively, with a 1-month wash-out period in between. Interrater reliability was assessed using Fleiss' κ, and changes in cyst classes between the versions were assessed using the Wilcoxon signed-rank test.

Results: Fleiss' κ values for interrater reliability were 0.354 (0.286-0.431) for 2005 and 0.373 (0.292-0.487) for 2019, indicating fair to moderate agreement. A significant decrease in cyst grades was noted using the 2019 version (Z = 3.49, r = 0.55, P < 0.001) among all cysts assessed by residents and only in complex cysts assessed by consultants (Z = 1.907, r = 0.275, P = 0.048).

Conclusion: Interrater agreement was similar for both classifications, ranging from fair to moderate. The 2019 version increased the proportion of masses downgraded to lower classes. Comprehensive training may enhance reliability and accuracy.