ASD ASSESMENTS
Terms and Concepts

Diagnosing ASD can be difficult since there is no medical test, like a blood test, to diagnose the disorder. Doctors look at the child's behavior and development to make a diagnosis. 

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The diagnosis procedure for ASD is a two step process. It consist of the following:

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• Developmental Screening

• Comprehensive Diagnostic Evaluation

This is a type of evaluation that measures an individual's performance against a set of predetermined standards or criteria. In the U.S., these tests are often tied to state standards.These assessments are different from norm-referenced assessments, which compare a individual's performance to the performance of a group.

A standardized assessment measures and compares your child to a large group of same age/grade level children. Standardized assessments are administered individually under controlled conditions to maximize accuracy and achieve uniformity across administrations.  There are numerous standardized assessments. The following are a few of the most popular and most used standardized assessments:

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• Autism Diagnostic Observation Schedule (ADOS)

• Childhood Autism Rating Scale (CARS)

• Wechsler Intelligence Scale for Children 5th Edition (WISC-V)

• Vineland Adaptive Behavior Scales 2nd edition (Vineland2)

Neuropsychological assessments involve the comprehensive evaluation of intellectual, attentional, executive, social-cognitive, language, and motor functioning. Such assessments are used to characterize areas of strength and weakness, inform differential diagnosis, guide treatment planning, and evaluate change over time. 

Behavioral assessments help identify the reason (function) behind challenging behaviors and help to create customized treatment plans. The most common type of behavioral assessment is a Functional Behavior Assessment (FBA).  An FBA uses three main methods to identify the cause of challenging behaviors: Indirect, Observational (direct), and Functional Analysis (FA). 

A normal distribution, also called a bell curve, occurs when variables (i.e., test scores) plotted on a graph fall into a regular distribution around a single mean.  68% of data points (test scores) fall within one standard deviation of the mean and approximately 95% of data points fall within two standard deviations of the mean. 

Standard scores are comparison scores. They allow clinicians to compare a test-taker's results to those of same-age peers.

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• Mean- The "average" score is calculated by adding all data points and dividing by the number of data points. 

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• Median- The central or middle score in a data set. The median is calculated by arranging scores from smallest to largest and locating the central score (score in the middle).

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• ​Mode- The score that appears most frequently in a data set. The mode can be calculated by putting the scores in order, then counting how many scores appear most often in the data set. 

The average distance (points) between all test scores and the average score. Standard deviations are calculated by test authors. Standard deviations are "average differences" from what most people score on a test.

Ranges provide a way to understand where an individual’s score falls relative to the average performance of the normative population. Each assessment may slightly vary in terms of terminology, but these general ranges are widely used. 

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Just because an individual falls in the "average" range does not mean there is not a need for concern. A score could fall within the 16th percentile and still fall within the average range. That means that the individual had 84% of their peers score better on the same assessment. That shows signs for concern. 

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Here's a basic breakdown of common ranges associated with standard scores and percentiles:

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• Average Range:

  • Standard Score: 85-115

  • Percentile: 16th to 84th

  • This range indicates that the individual's performance is similar to the majority of the population.

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• Below Average (or Low) Range:

  • Standard Score: 70-84

  • Percentile: 2nd to 15th

  • This range suggests that the individual is performing below the typical range but may still have some functional abilities.

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• Significantly Below Average (or Very Low) Range:

  • Standard Score: Below 70

  • Percentile: Below the 2nd

  • This range reflects significant challenges and indicates a need for considerable support in the areas assessed.

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• Above Average Range:

  • Standard Score: 116-130

  • Percentile: 85th to 97th

  • This range suggests stronger-than-average abilities in the measured area.

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• Significantly Above Average (or Very High) Range:

  • Standard Score: Above 130

  • Percentile: Above the 98th

  • This range indicates exceptional performance or abilities compared to the normative group.

Represents how a score compares to scores of others within a particular comparison group. Percentile scores range from the 1st  through 99th percentile, indicating the percentage of scores in the comparison group that are lower or higher than the test taker’s score. 

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Percentile ranks are not equal units. Percentile ranks cluster around the mean, and they stretch out at the high and low ends of the bell curve.

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Percentile ranks offer more of an indicator of where an individual scores compared to a whole and can offer an insight if there is a need for concern. For example, a standard score of 100 equals a percentile rank of 50. That means that 50% of individuals scored better than the individual being looked at.