A Psychometric Evaluation of the Motor-Behavioral Assessment Scale for Use as an Outcome Measure in Rett Syndrome Clinical Trials.
Melissa Raspa, Carla M Bann, Angela Gwaltney and 15 others
PMID 33211820WHAT IT FOUND
The revised Motor-Behavioral Assessment Scale works best as a single total score rather than separate subscales.
Its 24 items reliably capture overall Rett syndrome severity, correlating strongly with clinical status and genetic mutation type, making it a valid outcome measure for trials.
Key findings
01The original three conceptual domains of the assessment did not hold up statistically; a five-subscale structure emerged instead, but the authors recommend using the total score of 24 items because subscale reliability varied.
02The total score showed very strong correlation with the Clinical Severity Scale and demonstrated expected differences based on MECP2 mutation severity, supporting its validity as a measure of overall Rett syndrome severity.
03Item response theory analysis showed that most items had acceptable discrimination, though some items within the respiratory behaviors subscale were less effective at distinguishing between patients with varying levels of severity.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
The sample lacked socioeconomic and racial diversity, as participants had to be seen in person at specialized Rett clinics, limiting generalizability to underserved populations. The study used baseline data only, so it does not demonstrate the tool's sensitivity to change over time, which is critical for clinical trials. Validity was assessed against a non-validated parent-report form (Interval History Form) rather than an established independent measure. Test-retest and inter-rater reliability were not assessed in this study.
The easy way to misread this
Do not use the individual subscales (such as social skills or aberrant behavior) as primary endpoints in clinical trials. Their internal consistency was low, and the authors explicitly recommend using the total score of 24 items instead.