Standardizing ADOS scores for a measure of severity in autism spectrum disorders

Abstract

The aim of this study is to standardize Autism Diagnostic Observation Schedule (ADOS) scores within a large sample to approximate an autism severity metric. Using a dataset of 1,415 individuals aged 2-16 years with autism spectrum disorders (ASD) or nonspectrum diagnoses, a subset of 1,807 assessments from 1,118 individuals with ASD were divided into narrow age and language cells. Within each cell, severity scores were based on percentiles of raw totals corresponding to each ADOS diagnostic classification. Calibrated severity scores had more uniform distributions across developmental groups and were less influenced by participant demographics than raw totals. This metric should be useful in comparing assessments across modules and time, and identifying trajectories of autism severity for clinical, genetic, and neurobiological research.

Figure 1

Age by language level calibration cells. Note. N’s denote the number of ASD participants within each cell.

Figure 2

Distributions of ADOS raw total scores by age/language cells (ASD assessments only).

Figure 3

Distributions of calibrated severity scores by age/language cells (ASD assessments only).

Figure 4

Distributions of calibrated severity scores by diagnostic group.

Figure 5

Case summaries of longitudinal severity scores. Note. Parentheses by individual data points indicate (Module, Raw Score) for each assessment. Caption. The calibrated severity metric allows change across time and module to be evaluated in a standardized fashion in children of varying age and verbal ability. Adam and Daniel follow relatively consistent trajectories despite module changes, while a marked change in severity is apparent in Cara’s scores despite seemingly small increases in raw total within the same module. Bianca’s decreasing raw totals alone indicate a drop in ASD severity, but the clinical import of this is obscured by her module change and increasing chronological age. Severity scores are not necessarily more stable than raw totals, but were created to allow the change or consistency in these cases to be interpreted more readily than perceived patterns in raw total scores.