Reliability of a scoring system used for qualitative evaluation of lymphoscintigraphic imaging of lower extremities

Abstract

Introduction: Lymphoscintigraphy is an imaging technique to diagnose and characterize the severity of edema in upper and lower extremities. In lymphoscintigraphy a scoring system can increase ability of diagnostic differentiation but the use of any scoring system requires sufficient reliability. Aim: To determine inter- and intraobserver reliability of a proposed scoring system used for visual interpretation of lymphoscintigraphic imaging of lower extremities. Materials and Methods: Lymphoscintigrams in 81 persons were randomly selected from our database for retrospective evaluation. These scans were assessed according to the criteria of a scoring system by two nuclear medicine physicians at two different time-points with a three month interval. The scoring system included 8 criteria for visual interpretation of lymphoscintigraphy imaging of lower extremities. The total score was the sum of all evaluating criteria with a potential range from 0 (normal lymphatic drainage) to 58 (severe lymphatic impairment). It was used the Wilcoxon signed-rank test, percentage of agreement, weighted kappa and Intraclass Correlation Coefficient (ICC) with 95% confidence intervals for investigation of the intra- and interobserver reliabilities of the scoring system. It was also categorized the differences of the total scores in 7 different categories for graphic comparison between/within the raters. Results: It was found some differences of the ratings between the raters, which were not statistically substantial. There were high or very high percentages of agreement between the raters from 82.7% to 99.4% and within the raters from 84.6% to 99.4%. It was found moderate to very good kappa correlations of inter- or intraobserver reliability of each sign of the scoring system. The total scores obtained from all signs had good inter- and intraobserver reliability. Regarding the comparison between the raters 66% and 64% of differences of the total scores are within plus/minus one scale point[-1, +1], and regarding the comparison within the rate 68% and 72% of the total score differences are within plus/minus one scale point[-1, +1]. Conclusion: The scoring system used for visual qualitative evaluation of lymphoscintigraphy of lower extremities is a reliable tool for evaluating lymph transport problem in patients with lymphedema in lower extremity.