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P0594 - Interpreting brain parenchymal fraction by comparison to healthy volunteers: Initial results from the MS PATHS normative sub-study (ID 1646)



Mean rates of brain atrophy in healthy controls range from 0.05-0.5%, depending on age and technical factors, including scanner, acquisition sequences, and image analysis techniques. In MS PATHS (MS Partners Advancing Technology for Health Solutions), standardized MRIs are analyzed using a software prototype (MSPie, MS PATHS Image Evaluation) that incorporates a novel approach to calculate BPF. Normative ranges measured using MSPie are needed to distinguish age- and disease-related changes.


To establish a normative reference for interpretation of brain parenchymal fraction (BPF) in individual MS patients relative to age-matched healthy volunteers (HV).


HV aged 21-60 were recruited at 6 MS PATHS sites to be age-, race-, and gender-matched to the MS PATHS cohort. HVs were imaged at baseline and once/year using 3T scanners (Siemens Healthcare, Erlangen, Germany) and standardized acquisitions (3DFLAIR and 3DT1), as in routine MRIs in MS PATHS. MRIs from UK Biobank supplemented the normative dataset past the age of 60. All MRIs were analyzed with MSPie to calculate BPF. BPF normative percentile were calculated for each age using quantile regression. Mean annualized rate of brain atrophy was estimated from HVs with follow-up MRIs. BPF percentiles were applied to the MS PATHS cohort. Mean Processing Speed Test (PST) z-scores were compared in MS patients stratified based on BPF percentiles.


209 HVs were enrolled, 590 UKBiobank HVs were selected, and 9479 MS patients had at least one MRI. HV BPF values ranged from 0.855-0.895 in the 21-30 age group to 0.796-0.882 in the 61-73 age group, demonstrating accelerating and more variable atrophy with increasing age. For MS patients age 21-73 years (n=6791), mean age-adjusted BPF percentile was 27.8%, where BPF values fell above the 50th%-ile in 23.4% (“mild MS”) and below the 25th%-ile in 57.6% (“severe MS”). Mean PST z-scores differed in BPF-based mild MS vs. severe MS groups (-0.15 and -0.83; p<0.001). Mean annualized BPF change in HV was -0.08% (range: -0.71% to +0.57%) based on 71 subjects (mean age: 41.1 years) with >2 MRIs.


Incorporating normative reference data into MSPie will aid clinicians with interpretation of individual patients’ BPF in clinical practice and may enable patient stratification based on BPF and other predictors. Additional longitudinal normative data are being collected to contextualize disease progression as measured by BPF change over time.

Disclosures: MS PATHS is sponsored by Biogen.