Expressive language sampling as a source of outcome measures for treatment studies in fragile X syndrome: feasibility, practice effects, test-retest reliability, and construct validity

Abstract

Background: The evaluation of treatment efficacy for individuals with fragile X syndrome (FXS) or intellectual disability (ID) more generally has been hampered by the lack of adequate outcome measures. We evaluated expressive language sampling (ELS) as a procedure for generating outcome measures for treatment research in FXS. We addressed: (a) feasibility, (b) practice effects over two administrations, (c) test-retest reliability over the repeated administrations, and (d) construct validity. We addressed these issues for the full sample as well as for subgroups defined by age, IQ, and ASD status. Methods: Participants were 106 individuals with FXS between ages 6 and 23 years who had IQs within the range of intellectual disability (IQ < 70). ELS procedures for collecting samples in conversation and narration were followed and analyzed separately. Five measures were derived from transcripts segmented into C-units (i.e., an independent clause and its modifiers): number of C-units per minute (talkativeness), number of different word roots (vocabulary), C-unit length in morphemes (syntax), percentage of C-units containing dysfluency (utterance planning), and percentage of C-units that were fully or partly unintelligible (articulatory quality). ELS procedures were administered twice at 4-week intervals for each participant. Standardized tests and informant reports were administered and provided measures for evaluating construct validity of ELS measures.

Expressive language development in adolescents with Down syndrome and fragile X syndrome: change over time and the role of family-related factors

“…See Abbeduto et al [16] for details of the transcription process. The scripted versions of conversation and narration described here yield highly reliable and valid estimates of talkativeness, dysfluency, lexical diversity, and MLU for individuals with ID of the ages studied and allow for discrimination of different etiological groups [55,56,60,103]. This is true even with samples per participant considerably less than the 100 utterances traditionally thought to be an adequate target for research [30,44].…”

“…In the present study, therefore, we used naturalistic procedures for obtaining conversational and narrative language samples that have been developed and standardized for use with verbal individuals with ID [16,[53][54][55]. These expressive language sampling (ELS) measures have a wide age and ability level range of use, from the early school years through adulthood for TD individuals as well as for those with ID [56]. ELS conversational and narrative procedures pose somewhat different demands on speakers and thus, together provide a more comprehensive characterization of expressive language ability than is possible with any single measure.…”

“…Compared to other expressive language measures derived from the typical norm-referenced standardized tests, these expressive language measures are more likely to be generalizable to real-world activities meaningful for the individual with ID [62]. In addition, these measures all display minimal practice effects and have strong test-retest reliability for individuals with FXS and DS in the age range interest, which is important in longitudinal studies that, by definition, involved repeated administration of the same measures [56,63]. Finally, intervention studies in individuals with different neurodevelopmental disorders have shown change in various ELS measures in the face of a lack of change in standardized tests [64][65][66].…”

“…Expressive language Expressive language skills were assessed through both a conversation and a narration activity, each designed to elicit spontaneous language in meaningful social activities [53]. These activities were scripted to increase consistency in examiner behavior, content of talk, and nature of the interaction, thereby ensuring comparability of the language samples across participants and occasions of measurement [22,56].…”

Evaluating Social Interactions Using the Autism Screening Instrument for Education Planning-3rd Edition (ASIEP-3): Interaction Assessment in Children and Adults with Fragile X Syndrome

“…The CDC FORWARD Component-C projects (RFA# U01DD001190) were funded with the goal of evaluating new outcome measures in FXS and documenting the longitudinal trajectory of FXS cognitive and behavioral profiles over one's lifespan. Progress has been made over the past 5 years in the Fragile X field by evaluating more objective outcome measures that do not involve parental reporting, including measures of attention [40], expressive language [41,42], and executive functioning [43,44]. Eye tracking technology has been used to examine aspects of social attention while viewing videos [45,46], as well as in a naturalistic setting [47].…”