To establish guidelines for use by psychologists and school psychologists in preparing psychological reports that will be used to help determine eligibility for DDS services.
Connecticut General Statutes §1-1g requires that three basic criteria be present for an individual to be determined eligible for DDS services: (1) Standardized intelligence/cognitive test results show performance at least 2 standard deviations below the mean - usually a score of 69 or below; (2) evidence of deficits in adaptive behavior, and (3) evidence that both of these deficits were manifested before the age of 18.
Evaluation of Intelligence
- Intelligence/cognitive tests that may be used, but are not limited to, are the latest versions of the Wechsler Intelligence Scales, Stanford Binet Intelligence Test, Woodcock-Johnson Tests of Cognitive Abilities, and the Kaufman Assessment Battery for Children. If a test of non-verbal cognitive ability is necessary, then the Wechsler Non-Verbal Intelligence Test, Leiter International Performance Scale, Test of Nonverbal Intelligence, or RAVEN may be utilized. All tests of intelligence must be individually administered and standardized to an appropriate normative group, and provide a standardized intelligence quotient in conformance with the American Psychological Association’s Standards for Educational and Psychological Testing (1999).
- The Department expects that as it is Best Practice and required by professional guidelines, the most appropriate cognitive test is to be utilized given the person’s disability, as this is the only way to obtain a potentially valid measure. For example, it is not appropriate to use a verbally based test for someone with speech/language deficits or when English is not the primary language.
- Tests that are not considered appropriate to diagnose an intellectual disability include brief or abbreviated cognitive or adaptive tests. Testing formats that project unadministered subtest scores from those that are administered (i.e., partial or screening type instruments) should also be avoided.
- When reporting test results, all sub-scales/index standard scores must be reported and analyzed. Also, the test must be valid in that the statistically significant difference between all index/sub-scales should be analyzed to determine if the Full Scale Standard Score is a valid measure of cognition.
- The entire profile of scores should show evidence of significant intellectual deficits. One standard score (e.g., VIQ, PIQ or even FSIQ) is usually not sufficient in and of itself to diagnose an intellectual disability, but may be utilized along with other appropriate measures given co-existing conditions.
- Significant differences between all index standard scores and/or subtest standard scores must be analyzed to assess intellectual potential and to make a differential diagnosis of intellectual disability. Confounding factors such as a perceptual or motor disability, speech or learning disability, and/or major mental disorder that compromise test performance should be analyzed with the predictive validity of the test results. People with a diagnosis of intellectual disability may also have other disabilities, however, it is recommended that confounding factors be analyzed when making a diagnosis of intellectual disability.
- Psychotropic or behavior modifying medications can interfere with and depress test performance. Someone who is noted as ‘psychiatrically stable’ on these types of medication may well do better on testing than someone who is not stable. Factors such as distractibility, lack of interest, fatigue, or reduced motivation during testing should be noted. All such factors should be noted in the evaluation and are examined when an eligibility evaluation is done.
- Previous intelligence test performance, particularly those completed during the individual's developmental period, should be compared and analyzed with current test results. Omission of previous testing may delay determination of eligibility.
- Preferred tests of adaptive behavior include the latest versions of the Vineland, the Adaptive Behavior Assessment System (ABAS), Scales for Independent Behavior (SIB), and Comprehensive Test of Adaptive Behavior. All subscales should be reported, and the informant should be someone who best knows the person. It is often best to obtain more than one adaptive evaluation, as the individual may do better at school than at home for example.
- The general profile of scores should show a pattern of significant deficits.
- Any lifestyle evidence that contradicts test performance should be noted. Such evidence can include a consistent ability to function independently without supervision, or the ability to maintain a job requiring substantial independence and technical skill. Such abilities do not rule out an intellectual disability, but should be contrasted with a single point-in-time performance on a test.
- A chronic history of a major psychiatric disorder can lead to substantial limitations in independent functioning. Analysis of pre-morbid adaptive behavior should be included when available. As an example, a person with oppositional defiant disorder may not want to participate in adaptive activities measured on these tests. This does not necessarily signal a deficit in adaptive functioning or not knowing how to do the tasks, but rather an unwillingness to engage in these tasks.
- Environmental or structural limitations which might effect independent functioning should be analyzed, (i.e., currently living in a restricted environment).
- Documentation that both cognitive/intellectual and adaptive deficits (as defined above) must be present at the same time, and both must currently exist, and have existed (were manifested) before the individual was 18 years of age, is required.
- Review medical, psychiatric, and school records for a formal diagnosis of intellectual disability or documented evidence of functioning within the range of intellectual disability before the age of 18 years. Participation in a special education program is not sufficient to diagnose intellectual disability.
Guideline for Psychological Reports KJM_09.23.13