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what is the importance of Gordon Diagnostic System?

what is the importance of Gordon Diagnostic System?

Review of the Gordon Diagnostic System by ROBERT G. HARRINGTON, Professor of Educational Psychology and Research, University of Kansas, Lawrence, KS: The Gordon Diagnostic System (GDS) is a portable, solid-state, child-proof, microprocessor-based unit operating independently of a microcomputer (Post, Burko, & Gordon, 1990), designed to administer a series of three game-like tests. The GDS has been used primarily to provide a behavior-based measure of the vigilance or sustained attention span and self-control (Gordon, 1987) of children, adolescents, and adults with attention deficit/hyperactivity disorder. Vigilance and behavioral inhibition have been considered two of the central components in the diagnosis of attention deficit disorder in children and adults. The device also can be used to monitor responses to stimulant medication (Barkley, Fisher, Newby, & Breen, 1988; Brown & Sexton, 1988), as well as in the evaluation of AIDS-related complex (Saykin et al., 1990), closed head injury (Risser & Hamsher, 1990), Fragile X Syndrome (Hagerman, Murphy, & Wittenberger, 1988), and Alzheimer’s disease (Gordon, Beeber, & Mettelman, 1987). The GDS provides a reading or printout of the number of correct responses, incorrect responses, and failures to respond and comes complete with parallel forms of each task for retesting. The GDS has been cleared as a medical device by the Food and Drug Administration. Computerized assessment of ADD/Hyperactivity has arisen as a result of concern with the unreliability of diagnostic decisions based upon subjective clinical judgments, informal interviews, and rating scales standardized on small samples of clinic-referred children (Gordon, 1986, 1987). Approximately 1,300 nonhyperactive boys and girls, 4-16 years of age, were included in the standardization. Norms also are available for college students, adults, and geriatric populations. “An additional 1100 hyperactive and nonhyperactive protocols from various subject populations, including deaf, blind, emotionally disturbed, learning disabled, and Spanish-speaking have also been gathered” (Gordon, 1987, p. 57). One limitation of this standardization sample is that the selection was limited mostly to the upstate area of New York and thus the representativeness of the sample must be called into question. Currently, research is being conducted to extend the standardization of the GDS to represent a Puerto Rican sample (Bauermeister, 1986; Bauermeister, Berrios, Jimenez, Acevedo, & Gordon, 1990). Normative data are presented in Threshold Tables, which show score ranges demarcating Normal, Borderline, and Abnormal ranges of performance by age (4-5, 6-7, 8-11, 12-16 years). The author claims that the norms are not presented by sex or socioeconomic status because these variables are not correlated with GDS performance, but this finding is curious because other research has clearly shown a much higher prevalence of ADD/hyperactivity in males than in females (Ross & Ross, 1982). In studies conducted by the author of the GDS, tasks on the GDS have been found to have moderate but significant levels of test-retest reliability over 2 to 45 days (r = .60 or higher) and stability over a one-year time period (r = .52 or higher) (Gordon & Mettelman, 1988). The GDS also appears to correlate moderately but significantly with other neuropsychological instruments (Grant, Ilai, Nussbaum, & Bigler, 1990), behavior-based measures (McClure & Gordon, 1984), and a variety of teacher and parent ratings of attention deficit hyperactivity disorders (Gordon, Mettelman, Smith, & Irwin, 1990). In an independent study using a sample of 119 age 6 to 12 year, 11 month-old ADHD males, only two tasks, the number of correct responses for Vigilance and Distractibility Tasks, correlated consistently with other measures (WISC-R, the WRAT-R Arithmetic, Beery Test of Visual and Motor Integration, and various sensory-motor variable from the Halstead-Reitan neuropsychological battery) (Grant, Ilai, Nussbaum, & Bigler, 1990). Gordon defends this lack of concurrent validity with other major measures used in ADD diagnosis by contending that the GDS makes a unique contribution in the measurement of attention, not assessed by more traditional tests. Gordon also argues that efforts to validate the utility of the GDS have been limited by disagreement among professionals with regard to a consensus definition of ADD/Hyperactivity (Gordon, Di Niro, & Mettelman, 1988). Despite these arguments it would seem clear that this research suggests that continuous performance tests such as the GDS may be useful, but are insufficient alone in the diagnosis of difficulties in impulsivity or sustained attention in children. Scores from the GDS, such as the Efficiency Ratio (Gordon, 1979) and the Delay Task (McClure & Gordon, 1984; Barkley, 1991), have demonstrated some discriminant validity with regard to distinguishing accurately between groups classified as hyperactive and normal. In another study of school-referred children, the GDS discriminated among children classified as ADD and those identified as reading-disabled, overanxious, and normal (Gordon & McClure, 1983). In a recent study (Wherry et al., 1993) research failed to support the discriminant validity of any GDS score regardless of whether the Child Behavior Checklist-Teacher Report Form or the ADHD Rating Scale was used as a criterion measure. These authors concluded that teacher rating forms should remain the “gold standard” for identifying ADHD youngsters. In one recent study concerns were raised about the extent to which the GDS may underidentify children who are classified by parent and teacher reports as ADHD (DuPaul, Anastopoulos, Shelton, Guevremont, & Metevia, 1992). In fact, it has been found that although the GDS will classify a normal child as ADHD in only 2% of the cases (Gordon, Mettelman, & Di Niro, 1989), it will produce false negative classifications anywhere from 15 to 35% of the time depending on the age of the child, criteria for subject selection, and the combination of scores employed (Gordon et al., 1989; Trommer, Hoeppner, Lorber, & Armstrong, 1988). On the other hand, the Vigilance Task Commission Score has been found to be particularly sensitive to the effects of stimulant medication, especially at higher doses (Barkley & Edelbrock, 1986). There is definitely need for further validity studies. As Gordon (1987) himself has indicated, the mere computerization of a measure does not preclude the need for “meaningful studies of validity” (p. 54). Furthermore, because many of the validity studies related to the GDS have been conducted by its developers, Barkley (1991) has suggested that there is a need for validity studies replicated by other independent researchers. To evaluate consumer satisfaction with the GDS, Gordon (1994) sent a survey to a sample of 475 GDS users who were randomly selected from a list of 900 users. He found that the GDS was used most frequently in private practice to evaluate ADD in children and adolescents (89%) and adults (48%). Most used the GDS as part of a multifaceted test battery that included standardized behavior checklists of parents (89%) and teachers (86%), achievement and intelligence tests (75%), formal observations (50%), and interviews with the child and parent (33%). Users indicated that the GDS agreed with other clinical information in about 73% of cases and when it disagreed 92% of the clinicians saw the discrepancy as a justification for further evaluation rather than as test error. Eighty-four percent of clinicians felt that the GDS provided opportunities for direct observations of a child’s actual behavior in a standardized situation that requires attention and self-control. A somewhat disconcerting finding was that half the sample used the GDS, at least in part, because its objectivity helped “sell” the diagnosis to parents and schools. Eighty percent of the respondents marked either a 4 or 5, indicating that they were likely moderately or very confident with the final diagnosis of ADD when the GDS was used for confirmation as a part of a multidisciplinary battery. In summary, Continuous Performance Tests (CPTs) have a long history (Rosvold, Mirsky, Sarason, Bronsone, & Beck, 1956) and are playing an increasingly broader role in the assessment of attentional processes. Unfortunately, research on the ability of CPTs such as the GDS to discriminate children with ADHD from their normal counterparts or to detect stimulant drug effects is limited. Research is hampered, in part, by nuances in subject selection criteria for ADHD/Hyperactivity. “Studies employ different rating scales, laboratory measures, observational techniques and interviews in addition to varying cutoff scores and exclusionary criteria” (p. 539, Gordon, Di Niro, & Mettelman, 1988). There is a need for a generally accepted set of research criteria in defining a sample with ADD/Hyperactivity of the sort suggested by Barkley, Fischer, Newby, and Breen (1988). Furthermore, like most other CPTs the GDS relies on visually presented stimulus materials, despite the fact that there is recent research (Baker, Taylor, & Leyva, 1995) that indicates that auditory presentations of stimuli can increase the difficulty of tasks and should be considered in the evaluation of vigilance and impulse control. Nevertheless, instruments such as the GDS may in the future provide clinically useful, objective, convenient, and relatively inexpensive measures of sustained attention and impulse control for ADHD children, adolescents, and adults. As Gordon concedes, no score on the GDS should be the sole determinant of a diagnosis of ADHD. In fact, Rasile, Burg, Burright, and Donovick (1995) found that in a sample of college students the GDS is not a substitute for other commonly used tests of visual and auditory attention, including the Digit Span, Digit Symbol, and Arithmetic subtests of the WAIS-R, Kagan’s Matching Familiar Figures Test, the Visual Span Subtest of the Wechsler Memory Scale–Revised, and the Stroop. The GDS should be viewed as providing only one source of information to be integrated with other sources in reading a final diagnostic decision about the presence or absence of attentional problems. When compared to other automated CPTs on the market such as the Test of Variables of Attention (T.O.V.A., 13:336; Greenberg & Waldman, 1991) the GDS would appear to have a much greater amount of published research support and a longer history supporting its use in clinical settings. In conclusion, Barkley (1991) has argued that a thorough assessment of ADD/Hyperactivity should include direct observations of ADHD symptoms in their natural settings, but concedes that analogue observations such as the GDS may be more feasible. Despite this concession, Barkley (1991) has warned against claiming a lab measure as the single standard for the diagnosis of ADHD. Given this caveat, clinicians should consider the GDS to be one of the several useful tools they might employ in the determination of attentional problems of children, adolescents, and adults and researchers should find the GDS a rich source of data in studying this complex variable called attention.

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