Reliability assessment of international grading system for vesicoureteral reflux

The International Reflux Committee proposed a grading system for vesicoureteral reflux in 1985 which has been used extensively in everyday practice and research studies. Despite widespread use, based mainly on face validity, the interrater and intrarater reliability of this tool are not known. A tool cannot be considered valid unless it is reliable. Therefore, we estimated the interrater and intrarater reliability of the international grading system for vesicoureteral reflux.

A series of 28 voiding cystourethrogram studies were selected. The images were assembled in an electronic presentation in random fashion. Four pediatric radiologists, 5 pediatric urologists and 4 senior urology residents graded the studies. The images were then shuffled in a random fashion and re-rated after 7 days (total 728 observations). Cohen weighted kappa statistics were used to determine interrater and intrarater reliability. Subgroup analysis was then performed comparing the variability among the 3 groups of raters and different grades.

The average interrater reliability was 0.53 (95% CI 0.52-0.55, p <0.0001). Agreement in subgroups was 0.61 for urologists, 0.59 for residents and 0.56 for radiologists. The lowest agreement was shown in grade III (0.36) and the highest in grade I (0.98). The intrarater reliability was 0.86 (95% CI 0.77-0.95, p <0.001).

The international grading system for vesicoureteral reflux shows low interrater reliability for moderate degrees of vesicoureteral reflux whereas the intrarater reliability is high. Modification of this system may improve its reproducibility.