Quantitative Assessment of TIP-TOE Behavior in Autism Spectrum Disorder Subjects: A CROSS-Sectional Cohort Study

Background:

About one fourth of individuals with autism stand, and/or walk, and/or run on their tiptoes. Studies about quantitative assessment of Tip-toe behavior (TTB) are scarce relating to walking and running and absent relating to standing. In a previous cohort study, using a qualitative assessment we described three mutually exclusive clinical functional classes of TTB of increasing severity: TTB only during running (TTB1), TTB only during walking and running (TTB2) and TTB during standing, walking and running (TTB3).

Objectives:

The aims of this cross-sectional study are: 1) to quantify TTB during both a static and a dynamic test in our ASD sample; 2) to compare the intensity of TTB in the three TTB clinical functional classes and in the NO-TTB group.

Methods:

Our study sample included 45 ASD subjects (mean age: 13,15 years – 4,63 SD; 40 males) diagnosed according to DSM V criteria and under observation at our Institute. The confirmation and the severity of autism was established through ADOS-2. A therapist assessed the presence/absence of TTB during standing, walking and running using direct observation and interview of the main caregiver living with the child through a structured assessment. According to this assessment, 25 ASD subjects resulted not TTB, 3 resulted in TTB class 1, 10 in TTB class 2 and 7 in TTB class 3. The intensity of TTB expression during static and dynamic tests was quantified as percentage of time spent on the tip toes and as the percentage of toe steps, respectively. Both tests were conducted using standardized video recordings reviewed independently by two expert therapists.

Results:

The overall ADOS calibrated severity score (CSS) of all the subjects was 7.56 (1.71 SD). The overall ADOS CCS was 6,92 (1,55 SD) in NO-TTB, 8,15 (1,73 SD) in TTB1+2 and 8,71 (1,38 SD) in TTB3 (p = 0.02). The TTB time percentage values of the NO-TTB group during the static quantitative test was 0.25% (0.37 SD), while the time percentage values of the TTB1+2 was 1,82% (2,82 SD) vs 32,34% (31,82 SD) in TTB3 (table 1). We found a significant difference between each of the 3 groups (p < 0,02). In the NO-TTB group, during the dynamic quantitative test, the mean percentage of the TTB steps was 0.66% (1.48 SD), while it was 7,91% (5,71 SD) in TTB1+2 vs 60,93% (28,29 SD) in TTB3 (table 1). We found a significant difference between each of the 3 groups (p= 0.000)(fig 1). Moreover, we found a significant correlation (r = 0.702) between the quantity of TTB in the static and the dynamic test. Finally, we also found a significant correlation between the severity of TTB during both the static and the dynamic tests and the ADOS-2 CSS (r = 0.305 and r = 0.406 respectively).

Conclusions:

We quantified TTB using a new structured static and dynamic assessment test in our ASD sample. We found significant difference between NO-TTB and the 2 TTB subgroups. The TTB quantity in the static test is correlated with TTB quantity in the dynamic test.