Table 1.
Latent class variables for children with autism spectrum disorder enrolled in the Study to Explore Early Development (SEED)
| SEED data source | Latent class variables | Scores used in latent class analysis | Scores indicating impairment |
|---|---|---|---|
| Autism diagnostic observation schedule | Autism symptom severity | Total severity scores from 1 to 10 | Higher |
| Autism diagnostic interview-revised | Age at single word development | Item scores from 4 to 62 months | Higher |
| Age at walking | Item scores from 7 to 43 months | ||
| History of regression | Item score dichotomized into yes (regression in either language or social domains reported) or no (regression in language or social domains not reported) | ||
| Insistence on sameness | Item scores representing compulsions/rituals, difficulties with minor changes in routines, and resistance to trivial changes in the environment dichotomized into yes (any reported) and no (not reported) | ||
| Repetitive behavior with objects | Item score dichotomized into yes (reported) and no (not reported) | ||
| Repetitive motor mannerisms | Item scores representing hand and finger mannerisms and other complex mannerisms dichotomized into yes (any reported) and no (not reported) | ||
| Restricted interests | Item scores representing unusual preoccupations, circumscribed interests, and unusual attachment to objects dichotomized into yes (any reported) and no (not reported) | ||
| Self-injurious behaviors | Item score dichotomized into yes (self-injurious behavior reported) and no (no self-injurious behavior reported) | ||
| Unusual sensory response | Item scores representing unusual sensory interests, undue sensitivity to noise, and negative response to specific sensory stimuli dichotomized into yes (any reported) and no (not reported) | ||
| Birth certificate | Gestational agea | Gestational age scores from 23 to 43 weeks | Lower |
| Caregiver interview | Early recognition of epilepsy/seizure disorder | Item score dichotomized into yes (parent report of epilepsy/seizure disorder) or no (no parent report of epilepsy/seizure disorder) | Higher |
| Child behavior checklist | Aggressive behaviors, anxiety/depression, attention problems, emotional reactivity, somatic complaints, withdrawn behaviors | Domain t-scores from 50 to 100 | Higher |
| Child sleep habits questionnaire | Sleep problems | Total problems scores from 0 to 91 | Higher |
| Early Development Questionnaire | Problems with age at first social smile | Item scores dichotomized into yes (delayed social smile) and no (typical social smile) | Higher |
| Gastrointestinal Questionnaire | History of gastrointestinal symptomsa | Item score dichotomized into yes (history of gastrointestinal symptoms) or no (no history of gastrointestinal symptoms) | Higher |
| Current diet restrictions | Item score dichotomized into yes (diet restrictions) or no (no diet restrictions) | ||
| Mullen scales of early learning | Expressive language skills | Age equivalent scores from 2 to 70 | Lower |
| Fine motor skills | Age equivalent scores from 4 to 68 | ||
| Receptive language skills | Age equivalent from 1 to 69 | ||
| Visual reception skills | Age equivalent scores from 5 to 69 | ||
| Social communication questionnaire | Social communication abilities | Total scores from 1 to 35 | Higher |
a
These variables were ultimately dropped from the model because they did not distinguish latent classes