Fat fraction quantification of bone marrow in the lumbar spine using the LiverLab assessment tool in healthy adult volunteers and patients with Gaucher disease.

BACKGROUND: Magnetic Resonance Imaging is used for evaluation of bone in Gaucher disease (GD), but a widely available quantitative scoring method remains elusive. AIMS: The study purpose was to assess the reproducibility of the LiverLab tool for assessing bone marrow fat fraction (FF) and determine whether it could differentiate GD patients from healthy subjects. METHODS: Ten healthy volunteers and 18 GD patients were prospectively recruited. FF was calculated at L3, L4 and L5. GD patient bone marrow burden (BMB) score assessed by one observer. Inter and intra-rater agreement assessed with Bland-Altman data plots. Differences in FF between healthy volunteers versus GD patients and between subjects treated versus not treated assessed using two-sample t-tests. In GD patients, the relationship between FF, BMB and glucosylsphingosine was determined using the Pearson's correlation coefficient. RESULTS: Healthy volunteer mean FF was 0.36, standard deviation (SD) 0.10 (range 0.20-0.57). Intra and inter-rater SD were both 0.02. GD patient mean FF was 0.40, SD 0.13 (range 0.09-0.57). No statistical difference was shown between healthy volunteers and GD patients (P = 0.447) or between GD patients whether on enzyme replacement therapy or not (P = 0.090). No significant correlation between mean FF and total BMB (r = -0.525, P = 0.253) or between FF and glucosylsphingosine levels (r = 0.287, P = 0.248). CONCLUSION: Excellent reproducibility of LiverLab FF measurements across studies and observers is comparable to Dixon quantitative chemical shift imaging (QCSI). Lack of statistical difference between GD patients and controls may be explained by limited patient numbers, active treatment or mild disease severity in untreated patients.

Intraobserver and interobserver variability of the bone marrow burden (BMB) score for the assessment of disease severity in Gaucher disease. Possible impact of reporting experience.

AIM: To evaluate the intraobserver and interobserver agreement for bone marrow burden (BMB) scores for individual examinations and for the change in BMB score over time in the same patient. METHODS: A total of 119 sets of MR images of the lumbar spine and femora from 60 patients with Gaucher disease were included. Each set of MR images was scored using the BMB score independently by two experienced MSK radiologists. One radiologist performed a second read four weeks later. Intraobserver and interobserver agreement was assessed using Bland-Altman analysis and weighted kappa scores. RESULTS: BMB scores (n=119) demonstrated fair intraobserver agreement (weighted kappa=0.53) with a mean difference of -0.20 and 95% limits of agreement (LOA) of (-3.41, 3.01). Inter observer agreement was poor with weighted kappa 0.28 with mean difference of -0.16 and 95% LOA of (-4.45, 4.11). Change in BMB scores over time (n=59) demonstrated poor/fair intraobserver agreement (weighted kappa 0.41, mean difference-0.20 and 95% LOA (-4.35, 3.94)). Interobserver agreement was poor (weighted kappa 0.25, mean difference -0.12 with wide 95% LOA (-6.23, 5.99)). CONCLUSION: Significant interobserver, and to a lesser extent intraobserver, variation occurs with blinded BMB scoring of Gaucher disease.