CARS-2 Scoring Interpretation: ST vs HF Cutoffs and What They Mean

Your child's evaluation report includes a CARS-2 score, and the number looks manageable — maybe a 29 or a 33. But the meaning of that number depends entirely on which version of the CARS-2 was administered, and getting that wrong shifts the clinical interpretation dramatically.

Two Versions, Two Very Different Cutoffs

The Childhood Autism Rating Scale, Second Edition, comes in two forms:

CARS2-ST (Standard Version) is used for children under 6, or for individuals of any age with estimated IQs below 80 or significant communication delays.

CARS2-HF (High-Functioning Version) is used for verbally fluent individuals aged 6 and older with estimated IQs above 80.

Both versions rate 15 behavioral items on a 1-to-4 scale (with half-point increments), producing a Total Raw Score from 15 to 60. But the interpretive ranges differ substantially:

A raw score of 29 falls in the non-spectrum range on the Standard version but indicates mild-to-moderate autism symptoms on the High-Functioning version. A score of 35 means mild-to-moderate on the ST but severe on the HF. If the report doesn't specify which version was used — or if the wrong version was administered — the interpretation could be off by an entire severity category.

How the CARS-2 Differs From the ADOS-2

The ADOS-2 is an examiner-administered structured observation with a specific algorithm, cutoff scores, and Calibrated Severity Scores. The CARS-2 is a clinician-rated observational index — the evaluator scores behavioral items based on both direct observation and caregiver reports, then sums the ratings.

The CARS-2 doesn't use the standardized Social Affect and Restricted/Repetitive Behavior domain structure of the ADOS-2. Instead, it rates 15 areas including relating to people, imitation, emotional response, body use, object use, adaptation to change, visual response, listening response, taste/smell/touch response, fear or nervousness, verbal communication, nonverbal communication, activity level, intellectual functioning, and general impressions.

Because the CARS-2 incorporates caregiver-reported behavior alongside clinical observation, it uses information from different sources than the ADOS-2's single-session format. A difference between their classifications does not by itself establish where the child's behaviors are most visible; ask how the evaluator interpreted the results together.

What to Check in Your Report

First, confirm which CARS-2 version was used and verify it matches your child's profile. If your verbally fluent 8-year-old with an IQ of 110 was scored on the CARS2-ST instead of the CARS2-HF, the severity classification may be artificially low.

Second, look at which of the 15 items received the highest ratings. The individual item scores reveal specific areas of concern — sensory responses, adaptation to change, and relating to people each point toward different accommodation needs.

Third, compare the CARS-2 result against the other tools in the evaluation. If the CARS-2 identifies mild-to-moderate symptoms while the SRS-2 reports severe social impairment and the ADOS-2 says Non-Spectrum, ask how the evaluator integrated those findings with developmental history and other observations. No combination of scores establishes a diagnosis by itself.

The Autism Evaluation Report Decoder explains how each scoring tool fits into the diagnostic picture and provides a framework for translating CARS-2 findings into specific school supports.