Variable agreement between visual rating scales for white matter hyperintensities on MRI - Comparison of 13 rating scales in a poststroke cohort

Background and Purpose Previous reports on the frequency, extent. and clinical correlates of white matter hyperintensities (WMHIs) have been contradictory. The purpose of this study was to test whether part of this variation could be explained by the different properties of the visual WMHI rating scales used. Methods The periventricular (PVHIs) and deep white matter (DWMHIs) hyperintensities of 395 poststroke patients were systematically analyzed and transformed to correspond to 13 different rating scales. The scales were compared with the use of Goodman-Kruskal measures of association. The relative frequencies, means, and medians of PVHI and DWMHI grades as well as Spearman rank correlations between WMHI grade and hypertension were calculated. Results At best more than 80% of the patients received an equivalent WMHI grade by different scales, but at worst the corresponding values were only 0.4% for PVHI and 18% for DWMHI. At best different scales categorized patients similarly in regard to WMHI grade, but at worst the corresponding values were 8% for PVHI and 57% for DWMHI ratings. The distribution of WMHI grades also varied, and when the effect of age on WMHI was assessed, some of the scales had a ceiling effect and some had a Boor effect. Only 1 of the 7 PVHI, 5 of the 9 DWMHI, and 1 of the 3 combined rating scales showed a significant correlation with arterial hypertension, a putative risk factor for WMHIs. Conclusions Some of the inconsistencies in previous studies of WMHIs are due to differences in visual rating scales. Our findings may warrant international debate regarding harmonization of WMHI ratings.