Diagnosing Intellectual Disability Using the Diagnostic Adaptive Behavior Scale

Transcription

1 Diagnosing Intellectual Disability Using the Diagnostic Adaptive Behavior Scale Robert L. Schalock Schalock & Associates Marc J. Tassé The Ohio State University Giulia Balboni Università di Pisa

2 Bob Schalock AAIDD Conference - June 3, 2015

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5 Item Characteristics o Theta o Item Characteristic Curve o Item Difficulty o Item Calibration Standard Score Confidence Interval Sensitivity and Specificity

6 Item Response Theory (IRT) postulates that item characteristics are specific to the item and are considered invariant across groups. Theta=ability level on a latent trait (i.e. adaptive behavior) o Theta is essentially a z (or standard) score o Theta metric: Mean=0; Standard Deviation=1 An item characteristics curve: X axis=theta (ability); Y axis=probability of a correct response Item difficulty: point along the theta at which the probability of responding correctly=50% Item calibration: comparable to norming in Classical Test Theory

7 The Samejima Graded Response IRT model is used to compute the individual s Theta (i.e. ability level) based on their responses to the DABS items. The Theta is then converted into a standard score metric (mean=100; SD=15).

8 Confidence interval (CI) is the score-based interval within which the individual s true score falls. DABS: The Confidence Interval is based on +/-2 SEM around the obtained standard score (i.e. 95% CI) o Standard Error of Measurement (SEM) is the variation around a hypothetical true score for the person. o A test s SEM can be estimated from the standard deviation of the test and a measure of the test s reliability.

9 Sensitivity: The percent of DABS standard scores correctly including individuals who had a diagnosis of ID o DABS: 81-93%; Mean=88% Specificity: The percent of DABS standard scores correctly excluding individuals who do not have a diagnosis of ID o DABS: 89-90%; Mean=90%

10 Overview of the Diagnostic Adaptive Behavior Scale Marc J. Tassé The Ohio State University Nisonger Center

11 Acknowledgements CO-AUTHORS on DABS Robert L. Schalock, PhD, Hastings College Giulia Balboni, PhD, Università di Pisa Italy Henry (Hank) Bersani, PhD Sharon A. Borthwick-Duffy, PhD, University of California Riverside Scott Spreat, EdD, Woodland Center for Challenging Behaviors David M. Thissen, PhD, University of North Carolina at Chapel Hill Keith F. Widaman, PhD, University of California Riverside Dalun Zhang, PhD, Texas A&M University FUNDING American Association on Intellectual and Developmental Disabilities Administration on Intellectual and Developmental Disabilities

12 Construct of Adaptive Behavior AAIDD DSM-5 ICD-11 Significant deficits in one of the three Adaptive Behavior Domains: CONCEPTUAL SOCIAL PRACTICAL

13 Construct of Adaptive Behavior CONCEPTUAL language, functional academics, self-direction, money management, time concepts. SOCIAL interpersonal skills, responsibility, self-esteem, wariness / naïveté, follow rules, etiquette, social problem solving. PRACTICAL activities of daily living, occupational skills, safety, healthcare, travel.

14 Measuring Adaptive Behavior For the diagnosis of intellectual disability, significant limitations in adaptive behavior should be established through the use of standardized measures normed on the general population, including people with disabilities and people without disabilities. + Clinical Judgment DSM-5 (American Psychiatric Association, 2013) - AAIDD 11e (Schalock et al p. 43) American Psychiatric Association (2013). Diagnostic and Statistical Manual for Mental Disorders, 5 th edition. Arlington, VA: American Psychiatric Publishing. Schalock, R. L. et al. (2010). Intellectual disability: Definition, classification, and system of supports (11e). Washington, DC: American Association on Intellectual and Developmental Disabilities.

15 AB Scales adaptive behavior instruments (Schalock, 1999). Normed on gen. pop. & recommended for Dx of ID Adaptive Behavior Assessment System II Adaptive Behavior Scales: School Edition II Scales of Independent Behavior Revised Vineland Adaptive Behavior Scales II - Tassé et al. (2012) Schalock, R. L. (1999). The merging of adaptive behavior and intelligence: Implications for the field of mental retardation. In R. L. Schalock (Ed.), Adaptive behavior and its measurement: Implications for the field of mental retardation (pp ). Washington, DC: American Association on Mental Retardation. Tassé, M. J., Schalock, R. L., Balboni, G., Bersani, H., Borthwick-Duffy, S. A., Spreat, S., Thissen, D. T., Widaman, K. F., & Zhang, D. (2012). The Construct of Adaptive Behavior: Its Conceptualization, Measurement, and Use in the Field of Intellectual Disability. American Journal on Intellectual and Developmental Disabilities, 117,

16 Significant Deficits in AB On these standardized measures, significant limitations in adaptive behavior are operationally defined as performance that is approximately 2 standard deviations below the mean of either: (a) one of the following three types of adaptive behavior: conceptual, practical, OR social, or (b) an overall score on a standardized measure of conceptual, practical, and social skills. - AAIDD 11e (Schalock et al p. 43)

17 Normal Curve

18 D A B S DIAGNOSTIC ADAPTIVE BEHAVIOR SCALE

19 Exclusively diagnostic focus on cut-off; 4-21 years old Semi-structured interview (approx. 30 min) Tailored to the AAIDD tri-partite definition of adaptive behavior Short-precise assessment instrument (Total = 75 items) No maladaptive (or problem behavior) subscale; Expanded items related to higher order social adaptive skills Gullibility/Naïveté Avoid Victimization Use of Item Response Theory Features of the DABS (Tassé et al., in press) Scale development/item selection & Scoring Tassé, M. J., Schalock, R. L., Thissen, D., Balboni, G., Bersani, H. A., Borthwick-Duffy, S. A., Spreat, S., Widaman, K. F., Zhang, D., & Navas, P. (under review). Development and Standardization of the Diagnostic Adaptive Behavior Scale: Application of Item Response Theory to the Assessment of Adaptive Behavior.

20 DABS Administration o 4 21 years (person assessed) o Semi-structured face-to-face interview between INTERVIEW RESPONDENT o No self-report o Approximately 30 minutes (age forms) o Assess actual performance of adaptive behavior ratings should be based on respondent s direct observation and knowledge of the individual being assessed o Ratings: 0 = no, does not do 1 = does it with reminders 2 = does it sometimes independently 3 = yes, does it NS = No Score

21 INTERVIEWER Interviewer should be a professional (e.g., psychologist, social worker, teacher, etc.) who has completed at least a Bachelor s degree and has previous individual assessment experience. ASSESSED PERSON

22 RESPONDENT Respondent should know the individual being assessed very well and have had the opportunity to observe the person on a daily or weekly basis - respondents may be family members, friends, teachers, co-workers, direct-support staff, employers or other adults who meet the above criteria. ASSESSED PERSON

23 Rating Scale 0 No rarely or never does it. No Ability 1 Yes does it with reminders or assistance but rarely or never independently. Partial Ability 2 Yes does it sometimes independently but sometimes needs reminders or assistance. Partial Ability + 3 Yes does it always or almost always independently never or rarely needs reminders or assistance. Full Ability NS No Score. (used only exceptionally) o o o Lack of opportunity due to cultural, gender, and/or geographic/regional factors Lack of opportunity due to environmental constraints Respondent has no direct knowledge of individual s typical performance NS => SKIP => MISSING INFORMATION

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26 DABS: Sample Items CONCEPTUAL SKILLS: Arranges words alphabetically. Reads at least 10 words. States correct day, month and year of birth. States value (in cents) of penny, nickel, dime & quarter. Adapts activities to coincide with the current season or weather conditions. Manages own money. Makes a list (e.g., things to do, things to buy). Sets a clock or watch to the correct time.

27 SOCIAL SKILLS: DABS: Sample Items Asks for help when needed. Says hello or hi and good-bye or bye when coming and going. Stands a comfortable distance from others during conversations, as appropriate for culture. Discusses differences of opinion. Follows rules and regulations when playing games (e.g., board games, sports, etc.). Shows emotions/feelings appropriately. Recognizes when her/his rights are being violated. Uses a variety of strategies that are effective in resolving social problems. Recognizes signs that someone is trying to exploit her/him.

28 PRACTICAL SKILLS: DABS: Sample Items Adjusts the water temperature at the faucet. Uses the restroom. Tests hot liquids/foods before drinking/eating. Wears clean clothes. Follows a daily schedule. Discriminates between potentially dangerous items from safe ones. Maintains steady work pace and quality under pressure. Makes local travel arrangements. Makes purchases relative to his/her budget/means.

29 Scoring Computer scoring of DABS * 95% confidence interval = ± 2 SEM

30 DABS: Summary Standardized adaptive behavior scale Normed on the general population Focused on diagnostic information Age: 4 21 years Total Items: 75 Conceptual Skills = 25 items Social Skills = 25 Practical Skills = 25 Administration semi-structured interview Computer scoring based on IRT model Standard Scores: Conceptual Skills (Mean = 100; SD = 15) Social Skills (Mean = 100; SD = 15) Practical Skills (Mean = 100; SD = 15) DABS Total Score (Mean = 100; SD = 15)

31 139 th AAIDD Annual Meeting Louisville, KY, June 1-4, 2015 Concurrent Session: Diagnosing Intellectual Disability Using the Diagnostic Adaptive Behavior Scale DABS Scores and Reports: What to Do With Them and How Dependable They Are Giulia Balboni University of Pisa, Italy

32 Background DABS was developed to facilitate the diagnosis of ID of 4-21 y.o. individuals allow to determine if the individual presents the significant limitations in AB necessary for the ID diagnosis

33 Background Significant limitations in AB are operationally defined as performance that is approximately 2 SDs below the mean of either (a) one of the following three types of AB: (b) or an overall score on a standardized measure Standard Error of Measurement of the AB scale must be considered in the determination of the cutoff point Conceptual Social Practical Conceptual Social Practical

34 Classification of the severity of ID into must be based on the severity of impairment of AB and no longer of intellectual functioning (i.e., IQ scores) Background Mild Moderate Severe Profound

35 Background Few of all the existing scales of AB have been considered valid and reliable to identify the significant limitations in AB DABS has several unique features that should increase its reliability and validity (e.g., DABS has been developed based on the IRT theory)

36 Goals To present: (1) how the SS on the DABS and shown in the Scoring Report can be used in the ID diagnostic process (2) how dependable the SS on the DABS is for ID diagnosis to briefly summarize its validity

37 DABS y.o. Conceptual Social Practical Skills Total AB skills score

38 ID Diagnosis Cut-off Point 3 DABS Domains, Total AB skills Standard Score - obtained with IRT model - Mean = 100 SD = 15 2 SDs below the mean cut-off = 70 SS

39 ID Diagnosis Cut-off Point To take into account the variability of the individual s score caused by several potential sources of measurement errors 2 SEM must be added to this ID diagnosis cut-off SS 3 DABS FORMS SEM Domain Conceptual SS 3 Social SS 3 Practical SS 3 ID Diagnosis Cut-off SS Total AB skills SS 2 74

40 ID Diagnostic Process SEM must be taken into account also for the computation of the SS obtained by the individual in the DABS For each SS on the DABS domains and Total AB skills: SS 2 SEM = 95% Confidence Interval

41 Goal: 1. To present how the SS on the DABS and shown in the Scoring Report can be used in the ID diagnostic process

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47 It can be said that John meets the ID diagnosis criterion of significant limitations in AB ID diagnosis cut-off SS 76 74

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49 ID Diagnostic Process If John meets also the ID diagnosis criterion of significant limitations in intellectual functioning it could be said that John has an ID disorder Based on the severity of impairment in AB, the ID could be classified as mild

50 Goal: 2. To present how dependable the SS on the DABS is for ID diagnosis summarize its validity How valid the DABS is in measuring AB around the cut-off point for determining significant limitations in AB

51 Sensitivity & Specificity Ability of the DABS in correctly identifying individuals with and without ID based on their results on the Scale (1) Sensitivity Percentage of all the individuals WITH an ID diagnosis who have a DABS SS BELOW the ID cutoff point (2) Specificity Percentage of all the individuals WITHOUT an IDdiagnosis who have a DABS SS ABOVE the cut-off

52 Sensitivity & Specificity Participants: DABS normative sample Age Mean (SD) Range TOTAL (n = 1,058) 11.1 (4.9) 4-21 Gender (%) Male - Female Diagnosis (%) ID Non ID 12-88

53 Sensitivity & Specificity DABS Form SENSITIVITY (%) SPECIFICITY (%) 4 8 y.o y.o y.o Mean 88 90

54 Sensitivity & Specificity DABS Form SENSITIVITY (%) SPECIFICITY (%) 4 8 y.o y.o y.o Mean 88 90

55 Sensitivity & Specificity DABS Form SENSITIVITY (%) SPECIFICITY (%) 4 8 y.o y.o y.o Mean 88 90

56 Sensitivity & Specificity DABS Form SENSITIVITY (%) SPECIFICITY (%) 4 8 y.o y.o y.o Mean 88 90

57 Sensitivity & Specificity DABS Form SENSITIVITY (%) SPECIFICITY (%) 4 8 y.o y.o y.o Mean 88 90

58 Sensitivity & Specificity DABS Form SENSITIVITY (%) SPECIFICITY (%) 4 8 y.o y.o y.o Mean 88 90

59 Sensitivity & Specificity DABS Form SENSITIVITY (%) SPECIFICITY (%) 4 8 y.o y.o y.o Mean 88 90

60 Sensitivity & Specificity DABS Form SENSITIVITY (%) SPECIFICITY (%) 4 8 y.o y.o y.o Mean (1) Sensitivity: 88% of the normative sample with a formal diagnosis of ID obtained a DABS SS BELOW the ID cut-off point in at least one domain (2) Specificity: 90% of the individuals WITHOUT an ID diagnosis obtained a DABS SS ABOVE the cut-off

61 Sensitivity & Specificity DABS Form SENSITIVITY (%) SPECIFICITY (%) 4 8 y.o y.o y.o Mean These results are particularly relevant given that the purpose of the DABS is to determine whether the individual presents the significant limitations in AB necessary for an ID diagnosis

62 Convergent & Divergent Validity Convergent and divergent validity of the DABS in comparison with the Vineland-II Scale D A B Conceptual Social Practical Vineland-II Communication Socialization Daily Living Skills Composite S Total

63 Convergent & Divergent Validity Convergent and divergent validity of the DABS in comparison with the Vineland-II Scale D A B S Vineland-II Communication Socialization Daily Living Skills Conceptual + Social Practical Total Composite

64 Convergent & Divergent Validity Convergent and divergent validity of the DABS in comparison with the Vineland-II Scale D A B S Vineland-II Communication Socialization Daily Living Skills Composite Conceptual Social Practical Total

65 Convergent & Divergent Validity Age Mean (SD) Range Participants TOTAL (n = 28) 11.5 (5.1) 4-21 Gender (%) Male - Female Diagnosis (%) ID Other NDD With the same interviewer interviewing the same respondent

66 Convergent & Divergent Validity D A B S Vineland-II Communication Socialization Daily Living Skills Composite Conceptual Social Practical Total

67 Convergent & Divergent Validity D A B S Vineland-II Communication Socialization Daily Living Skills Composite Conceptual Social Practical Total Convergent correlations obtained between the domains of the two instruments that measure the same AB skills are very high

68 Convergent & Divergent Validity D A B S Vineland-II Communication Socialization Daily Living Skills Composite Conceptual Social Practical Total They are generally higher than the corresponding divergent correlations between each of the DABS domains and the other Vineland-II scales which measure different areas (reported in the rows)

69 Convergent & Divergent Validity D A B S Vineland-II Communication Socialization Daily Living Skills Composite Conceptual Social Practical Total

70 Convergent & Divergent Validity D A B S Vineland-II Communication Socialization Daily Living Skills Composite Conceptual Social Practical Total

71 Convergent & Divergent Validity D A B S Vineland-II Communication Socialization Daily Living Skills Composite Conceptual Social Practical Total

72 Convergent & Divergent Validity D A B S Vineland-II Communication Socialization Daily Living Skills Composite Conceptual Social Practical Total These results are particularly relevant given that the Vineland-II Scale is one of the most valid scales of AB available

73 In Conclusion DABS forms are valid and therefore the SS obtained may be used to verify if the individual presents the significant limitations in AB necessary for the ID diagnosis

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75 Diagnosing Intellectual Disability Using the Diagnostic Adaptive Behavior Scale Robert L. Schalock Schalock & Associates Marc J. Tassé The Ohio State University Giulia Balboni Università di Pisa