Longitudinal Trajectory of Adaptive Skills in Phelan-McDermid Syndrome.
In Phelan-McDermid syndrome, switch to Vineland GSVs to catch small but real gains in daily living and receptive language.
01Research in Context
What this study did
Srivastava et al. (2025) followed kids with Phelan-McDermid syndrome for two years. They gave the Vineland Adaptive Behavior Scales three times to see if skills grew, stayed flat, or dropped.
The team looked at both standard scores and growth-scale values, or GSVs. Standard scores compare a child to same-age peers. GSVs track raw skill growth, like learning to wash hands, no matter age.
What they found
Standard scores stayed flat or fell in every area. That looks like no progress, but GSVs told a different story.
GSVs showed small gains in understanding words, using written words, and daily tasks like dressing. Social skills did not budge even with GSVs.
How this fits with other research
Webb et al. (1999) saw Vineland scores rise with age in autistic kids. Siddharth et al. seem to disagree, but the key is the metric. J et al. used standard scores in a larger autism sample; Siddharth used GSVs in a rare syndrome where age-based growth is slower.
Deserno et al. (2017) also found flat functional scores over two years in kids with progressive brain disorders. Their result matches the flat standard scores here, showing the metric, not the kids, drives the picture.
Choi et al. (2022) warned that Vineland standard scores can hide real progress made in ABA. Siddharth et al. prove the same point in a genetic syndrome, backing the call to watch GSVs when treating slow-growing skills.
Why it matters
If you track Phelan-McDermid cases, stop using standard scores alone. Plot GSVs each quarter to spot tiny wins in communication and self-care. Share these graphs with parents so they see progress the percentile chart misses.
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02At a glance
03Original abstract
Phelan-McDermid syndrome (PMS), caused by SHANK3 haploinsufficiency, lacks natural history data. We report the trajectory of adaptive behavior from a prospective, longitudinal, natural history study. English-speaking people aged 3-21 years with a PMS molecular diagnosis were followed over 2 years. We analyzed longitudinal Vineland Adaptive Behavior Scales, Second Edition domain-level standard scores and subdomain-level growth scale values (GSVs) obtained at baseline, 12 months, and 24 months. We assessed within-subject time effects and cross-sectional age effects using linear mixed effects models. This sample included 99 participants (baseline age = 8.83 ± 4.58 years). Within-subject standard scores decreased/remained constant for all domains: Communication (slope of within-subject mean-centered age = -0.33 [95% CI -1.08, 0.41]; p = 0.38), Socialization (-1.25 [-1.95, -0.56]; p < 0.001), and Daily Living Skills (-0.35 [-1.37, 0.67]; p = 0.50). However, subdomain GSVs showed within-subject growth across several categories. Receptive (5.26 [2.49, 8.02]; p < 0.001) and Written (2.79 [1.11, 4.47]; p = 0.001) Communication GSVs increased. Personal (1.84 [0.81, 2.86]; p < 0.001) and Domestic (2.31 [0.98, 3.64]; p < 0.001) Daily Living Skills GSVs increased. Socialization subdomain GSVs did not change. PMS is characterized by impaired adaptive behavior and slow, small gains in communication and daily living, but not socialization skills, as measured by subdomain GSVs. Unlike standard scores, measuring performance compared to same-age peers, GSVs quantify an individual's progress, emphasizing the need for GSVs in interpreting developmental changes in PMS.
American journal on intellectual and developmental disabilities, 2025 · doi:10.1352/1944-7558-130.5.380