Discriminating Sensory Subtypes: A Multigroup, Multidimensional Item Response Theory Analysis

PURPOSE: To determine which items and domains on the Short Sensory Profile (SSP) best discriminate between sensory subtypes.

BACKGROUND: Sensory features are patterns of behaviors that influence the daily functioning of children diagnosed with neurodevelopmental disorders including autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD). Indeed, sensory features are now included in the diagnostic criteria for ASD, making the assessment of sensory features germane to comprehensive diagnostic testing.

One way to describe sensory features is through the use of sensory subtypes. Distinct sensory subtypes have been identified in children with ASD through parent responses on the SSP. Reduced assessment administration time and respondent burden are increasingly valued in today’s health care climate, leading to an increase in the development and utilization of short-form outcome measures. We conducted an Item Response Theory (IRT) analysis of the SSP as a first step toward the development of a more efficient and precise method of identifying sensory subtypes.

DESIGN: The present study is a nonexperimental secondary analysis.

PARTICIPANTS: One hundred fifty-five participants ages 4–10 yr were included in the present study. Diagnoses of participants included ADHD and ASD; controls were typically developing children.

MEASURES: Parents of study participants completed the SSP, a 38-item parent-report measure. The SSP is designed to measure behaviors associated with differences in the modulation of everyday, environmental sensory stimuli in children ages 3–10 yr in seven sensory domains. Parents respond to each item using a 5-point ordinal scale ranging from 1 (always) to 5 (never), with higher scores indicating more typical performance.

ANALYSIS: Participants were grouped into one of four sensory subtypes utilizing an established algorithm. Responses for each item were dichotomized by collapsing Categories 1–3 (always, frequently, and occasionally) and Categories 4 and 5 (seldom and never) due to the restricted range of response categories utilized for some questions when participants were grouped by sensory subtypes. Data were analyzed using flexMIRT^® with a 2PL graded response model. Item difficulty and item discrimination indices were examined to determine which items best distinguished between subtypes. Distributions were graphed using the subtype mean and standard deviation for each domain to determine which domains best distinguished between groups.

RESULTS: Item discrimination indices ranged from 0.71 to 7.33, and item difficulties ranged from –0.46 to –1.88. Six highly discriminative items across a range of item difficulties were identified. The low energy/weak, visual and auditory sensitivity, and tactile sensitivity domains appeared to best distinguish between sensory subtypes.

DISCUSSION: The efficient and precise identification of sensory features is critical because it is one part of comprehensive diagnostic testing for common neurodevelopmental disorders. The results of this study indicate that some items on the SSP are more influential than others in the determination of sensory subtype. It may be possible, then, to identify an individual’s sensory subtype using a reduced number of items. A shorter item set may improve the clinical utility of the sensory subtyping approach to evaluating and describing sensory difficulties.

IMPACT STATEMENT: The present study indicates that the use of a reduced item set from the SSP may be a promising way to increase efficiency and reduce respondent burden when determining sensory subtype membership.

FUNDING SOURCE: Wallace Research Foundation