Unlike the tests above, these tests are administered by doctors or specialized examiners. These are not simple screening tests yielding only a single yes or no score suggesting whether additional assessment should be performed. Instead, they are complex, covering multiple domains where developmental delays can occur, and yielding multiple scores reflecting these various domains. These tests are also not used in their raw form, but rather are compared against a reference group (called a normative sample) of thousands of other children's scores on the same tests. Reported scores reflect whether test subjects are above or below the average performance expected of normal non-PDD diagnosed children. While some of these tests can be administered by regular doctors, others require specialized training. Child psychologists and their assistants, known as psychometricians, administer and interpret these specialized tests.
- Checklist for Autism in Toddlers. The Checklist for Autism in Toddlers (CHAT) is a screening test that a pediatrician may use to determine if she should send a child on to a specialist psychologist or psychiatrist for further assessment. The CHAT is designed to be used with children who are at least eighteen months old. It is filled out by an examiner who answers questions based on personal observation of subject children, and on parental or guardian reports. The test addresses children's social development and also tests their ability to simultaneously focus on an object that another person is also paying attention to (joint attention). It considers children's ability to use imaginative play skills and their ability to point to objects on command. It measures eye contact and social reciprocity. The examiner considers her own observations and the parents' responses to nine questions concerning their child's behavior to determine whether the child in question appears to be at risk for a PDD like autism.
The push for earlier and earlier autism diagnoses has resulted in the M-CHAT, a shortened version of the CHAT designed to be filled out by parents. The questionnaire focuses on stereotyped movements, social reciprocity and imaginative play. Parents are directed to seek professional attention if their child's answers suggest symptoms of autism may be present. The M-CHAT is a relatively new instrument and as such is still under development and evaluation.
- The Childhood Autism Rating Scale. The Childhood Autism Rating Scale (CARS) consists of a list of fifteen questions probing five diagnostic domains relevant to autism spectrum disorders. The five domains include: relating to others, body use, adaptiveness to change, listening response and verbal communication. The test examiner answers these questions after observing the child subjects' behavior, reviewing reports concerning the child's behavior, and interviewing the parents, and then computes a CARS score which is compared to normative data that describe how typical children and children known to have PDD diagnoses score on the test. A child's CARS score thus helps examiners to know whether that child's behavior is most similar to a typical child's behavior, a child with mild autism, or a child with severe autism. CARS does not diagnose autism, but it does help identify who acts like an autistic person. http://www.patientcenters.com/autism/news/diag_tools.html#CAR
- Brigance Screens. The Brigance Screens address developmental milestones in twelve-month increments. There are a series of tests that are designed to measure an infant's or toddler's development in communication and language skills, social interactions, motor skills and self-help skills. The tests are segregated into four age-based categories: birth to twenty-three months; two to two-and-a-half years; three to four years; and kindergarten to first grade. Each age category is further subdivided into twelve-month increments. Test results are compared against normative data, and the results of those comparisons, which indicate degrees of age-corrected developmental delay within measured skill domains, indicate whether further evaluation and diagnosis might be appropriate.
- Bayley Scales of Infant and Toddler Development. The Bayley Scales (now in their third edition) are not simple questionnaires, but rather norm-referenced objective tests of infant and toddler development. They require expert administration by a trained child psychologist or psychometrician and cannot be administered or interpreted directly by parents or pediatricians. They are appropriate for use with children between one month and forty-two months old.
The Bayley Scales are designed to be age-sensitive. Test items are organized so as to be age appropriate for each child being tested. The examiner determines the subject child's age, and then uses set test items previously determined to be appropriate based on three-month developmental intervals.
The individual tests comprising the Bayley Scales II cover three different developmental domains: behavioral, mental and motor skills. The behavioral part of the Scales measures how well children can attend to tasks, maintain emotional control and tolerate the testing process. The mental Scales track children's language development, problem-solving skills, memory and perception. Finally, the motor skills portion of the Scales assess children's posturing, muscle control, gross motor skills and fine motor skills.
Scores from the Bayley Scales are used to construct a customized infant development charts for each test subject that places the subject's development in the context of average same-age children's development. Children who demonstrate developmental delays are seen to be impaired in reference to test norms which were created by administering the test to thousands of normal children of varying ages, and varying conditions such as premature birth status, illness and other variables that might account for developmental delays. Details about the Bayley Scales can be found at: http://www.pearsonclinical.com/education/products/100000123/bayley-scales-of-infant-and-toddler-development-third-edition-bayleyiii.html
- Wechsler Preschool and Primary Scale of Intelligence. The Wechsler Preschool and Primary Scale of Intelligence, abbreviated as WPPSI, is one of the oldest intelligence tests designed specifically to measure the cognitive abilities of preschoolers. The test yields Intelligence Quotient (IQ) scores, as well as subtest scores yielding additional domain-specific information. It is a revision of the original Wechlsler Scale of Intelligence, created in the late 1960's to measure IQ for children between four and seven years of age. The modern WPPSI, now in its third edition, is appropriate for children between the ages of two and six. Only a specially trained child psychologist or psychometrician can administer the WPPSI.
The WPPSI has been designed to measure a child's cognitive abilities without requiring the child to be able to read or write. The language portion of the test is oral and focuses on the child's receptive and expressive language skills. The WPPSI also measures the child's the child's ability to imitate and reason through block design and pattern completion subtests contained in the processing performance section. The test also measures general language skills in receptive activities and object labeling activities.
The WPPSI yields an overall "full-scale" IQ score, as well as separate verbal and performance IQ scores, and additional subtest scores, each norm-referenced so as to indicate relative strengths and weaknesses in relation to average test scores of normal children of the same age.
The IQ score is critical for assessing whether a mental retardation diagnosis is reasonable. IQ scores are set so that their average is always 100. Some 98% of children who take the test will achieve scores within 30 points plus or minus of that average figure. Scores below 70 can be indicative of mental retardation.