Diagnostic Evaluation (Determination of Intellectual Disability - DID)

All persons requesting intellectual disability services through The Harris Center must complete a diagnostic eligibility assessment and a financial eligibility assessment. Certain types of documentation must be submitted for both the financial and diagnostic assessments.

A psychological evaluation called the Determination of Intellectual Disability (DID) Evaluation will be conducted by a Texas Department of Aging and Disabilities (DADS) certified psychologist or Licensed Psychologist.  The DID determines if an individual has Intellectual Disability or a Pervasive Developmental Disorder (Autistic Disorder, Asperger’s Disorder, Rett’s Disorder, Childhood Disintegrative Disorder or Pervasive Developmental Disorder-NOS.) The DID will include a review of past testing, and interview with the individual and family members, and testing to determine the individual’s levels of intellectual and adaptive functioning.

• Review of Past Testing: The psychologist will review previous evaluation reports to help understand the individual’s historic levels of functioning. The review of past testing may also reveal improving or declining levels of functioning over time. Previous test results are also used to verify that Intellectual Disability existed before 18 years of age. 
• Interview: This typically includes the consumer and caregiver. The psychologist will usually ask about developmental history, family history, educational history, physical/medical issues, psychiatric history, problem behaviors, services needed and other concerns the family and consumer have.
• Adaptive Behavior Assessment: The psychologist administers an adaptive behavior assessment. The adaptive behavior assessment is performed by interviewing a person who is familiar with the consumer’s communication, self-help and social skills.  The individual’s adaptive behavior level is then compared to what is typically expected of persons in his or her age group to determine if the individual’s adaptive behavior level falls within the range of intellectual disability.
• Intellectual Assessment: The psychologist administers an intelligence test (IQ test) to determine if the individual’s level of intellectual functioning falls within the range of mental retardation. The IQ test is given to the individual directly and requires the individual to solve a variety of problems that measure reasoning abilities.

Documents Required for the DID Evaluation

• Assessment Reports from School: If the individual has received Special Education services, you must provide copies of their Full Individual Evaluations (FIE’s) and Comprehensive Individual Assessments (CIA’s) ahead of time for review. If you do not have copies of these evaluations, they can be requested from the school.
• Assessment Reports from Other Agencies: If the individual was seen by other agencies or professionals for suspected developmental delays, intellectual disability or pervasive developmental disorders, copies of these evaluations should also be provided. Examples include evaluations by:
  • Community Centers, State Schools or State Hospitals
  • Schools for the Deaf or Blind
  • Private hospitals or clinics
  • Private psychologists or psychiatrists
  • Other educational or training programs/agencies for persons with intellectual disability & related disabilities