Laboratory Measures of ADHD

1. Laboratory Measures of ADHD Adam B. Lewin November 19, 2003

2. What are Laboratory Measures?

4. Laboratory Measures • Techniques where behavior is observed under standardized conditions • Usually involving stimuli designed to evoke the specific behavior of interest • Excluded: • Naturalistic observations in unstandardized conditions • Techniques designed primarily to elicit & observe physiological responses. (Frick, 2000 – J Clin Child Psychology)

5. Laboratory Measures • Direct, systematic behavioral observations conducted in a clinic or research setting where efforts have been made to approximate more naturalistic situations (e.g., school, home, etc.). (Barkley, 1991 – J Ab C Psychology) • Often limited ecological validity

6. Laboratory & Performance-Based Measures • A Broader Perspective: • Techniques suitable for use in research settings • Often limited implementation clinically • Time consuming • Non-diagnostic • Despite clinical utility

7. Ecological Validity • The extent to which predictions based on a laboratory measure can be extended to naturalistic setting • e.g., Does the result of a laboratory task reflect actual attentional problems?

8. Ecological Validity: Barkley’s Criteria • 1. Does the laboratory measure show differences between ADHD & control groups? • 2. Correlations with other laboratory measures with well-established ecological validity • 3. Sensitivity to experimental manipulations know to affect the criterion • 4. Correlations with ecological criteria

9. Laboratory Measures • 142 studies comparing ADHD & normal controls • 439 comparisons • Variety of tasks & neurocognitive tests • Plethora of instruments employed • CPT, WISC-R, WCST, MMFT, Stroop • (Rapport et al., 2000)

10. Laboratory Measures • Reliable vs. unreliable instruments for detecting group differences • Reliable: CPT, WISC-R Coding & Arithmetic, Visual recall tasks • Unreliable: Tapping, pegboard, Trails A, WISC-R Mazes • Distinguishing characteristics: • Involve recall and/or recognition • Require use of the phonological loop • Pacing – experimenter controlled • Response stimulus not continuously displayed • (Rapport et al., 2000)

11. MEASURES OF ATTENTION

12. Continuous Performance Tasks • Originally designed to detect lapses in attention during seizures. • (Rosvold et al., 1956) • Usually computerized assessments of sustained attention • Can be visual, auditory, numerals, characters, shapes • Subject must respond to target embedded in a series of distracter stimuli

13. Continuous Performance Tasks • Three General Models: • (Rapport, 1993) • X-Version – respond to a target stimulus • Reverse X-Version: inhibit response to a stimulus • AX-Version – respond to a target stimulus only when it is preceded by a different target • Double Letter Version – respond only to an immediately repeated stimulus • (Friedman et al., 1978)

14. X

15. Continuous Performance Tasks • Assessment of sustained attention: • Number of Correct Responses • Errors of Omission (EO) • Number of Target Stimuli Missed • Believed to assess sustained attention & impulse control: • Errors of Commission (CE) • Responding after a non-target stimulus • (Sostek, Buchsbaum, & Rapoport, 1980) • Weakly correlated with error scores from the MFFT • Both CEs and OEs significantly correlated with CPRS & CTRS Hyp & Inattn scales • (Barkley, 1991)

16. Conners’ CPT • Computer-assisted assessment of attention • 14 minutes • X & Reverse X Versions; AX Version • 6 Trial Blocks; 3 Sub-blocks per trial • 20 Trials Each • Interstimulus interval varies from 1, 2 or 4 seconds

17. Conners’ CPT • Numerous output data: • Correct responses, OEs, CEs, reaction times, Index score • CPT-II: Clinical Confidence Interval • Norms for general population and children 4-18 diagnosed with ADHD • Low false positives and negatives (<10-15%) • Practice effects are minimal • Sensitive to pharmacological treatment changes

18. Conners’ CPT • Some Advantages/Disadvantages • Avoids false negatives by frequent target presentation • Chance of impulsive errors maximized due to the continuous level of responding • Questionable ecological validity • Correlates with analogue measures of attention (.25-.35) • Relates to parent & teacher ratings of inattention & hyperactivity • CPRS/CTRS & CBCL • (Barkely 1991)

19. Conners’ CPT II • Normative sample of 2,686 clinical and nonclinical subjects. • T-Scores & the following classifications: • markedly, moderately or mildly atypical, within the average range, and good or very good performance. • New confidence index that is the percentage out of 100 clients that would be correctly classified based on a profile. • CPT-II provides an overall index, for research comparisons with the CPT IAges 6 years and older • (Kiddie CPT for ages 4-5).

20. TOVA • Test of Variables of Attention (TOVA) • (Greenberg & Waldman, 1993) • Two 11-minute computerized tasks (one for children under age 5) • Easily discriminated visual stimuli • Square with a small square adjacent either to the top (target) or bottom • Attempts to eliminate confounds due to learning difficulties

21. TOVA • First task presents the target infrequently (1:3 ½ ) • Designed to elicit boredom & thus measure sustained attention • Second task presents the target frequently (3 ½ :1) • Designed to measure impulsivity • Normative data in 2-year intervals for children 4-19 (10 year intervals for adults) • Diagnostic utility not well documented

22. Auditory CPT • Tape of a 96-word list, of 20 different monosyllabic words, read 6 times • Target word is “dog” • 20 times per 96-word trial • Respond by giving “thumbs up” • Test-retest only .67-.84 • Scoring is difficult

23. Gordon Diagnostic System • Gordon Diagnostic System (GDS) • (Gordon, 1979) • Portable machine • Visual • Vigilance (numerical AX task) • Distractibility (Random numbers flash in proximity to the target) • Delay (points awarded for delaying response at least 6 seconds) • Measure of response inhibition • Correlates with hyperactivity ratings by parent & teachers • Not proven sensitive to medication effects

24. GDS • Auditory • Vigilance Task: Subject responds to numbers that are heard instead of seen • Interference Task: Random number through the headphones. The subject performs on the standard Vigilance (or Distractibility) tasks while having to contend with the confusing auditory input.

25. IVA • Intermediate Visual & Auditory CPT (IVA) • Half the targets are visual (the characters are a "1" and a "2“) and half are presented audibly through the computer's speaker • 13 minutes

26. Other CPT Tasks • Children’s Checking Task (CCT) • (Margolis, 1972) • Paper & Pencil • “Cancellation Task” • Mark numbers listed in rows on a page as they are read on a recording • Circle discrepancies between the list & recording • 30 minutes; Scores include OE & CE • Strong correlations with other measures of attention • Better ecological validity than other CPTs

27. Other CPT Tasks • Matching Familiar Figures Test (MFFT) • (Kagan, 1966) • Measure of attention and impulse control • Match-to-sample task • Identify the identical matching target picture from an array of six similar stimuli • 12 or 20 trial versions • Measures of response latency and errors • Fails to differentiate ADHD from controls & medication effects • Adolescent norms unavailable • Not recommended for clinical use

28. TEA-Ch • Test of Everyday Attention for Children (TEA-Ch; Manly et al., 1999) • Norms for ages 6-16 • 9 Game-like subtests • 3 Domains • Selective Attention (2 subtests) • Sustained Attention (5 subtests) • Attentional control/shift (2 subtests) • Approximately 2 hours to complete; subtests can be administered individually

29. TEA-Ch • Children with ADHD show significant impairment on sustained attention & attentional control tasks (compared to clinical controls) • Differences on selective attention tasks not significant. • Heaton et al., 2002

30. Neuropsychological Tests

31. Neuropsychological Measures • Stroop Word-Color • Timed test measuring the ability to inhibit or suppress automatic responses • High % of false negatives (53%) • (Barkely & Grodzinsky, 1994) • Trail Making Test • Trails B – Attentional Shift • Very high false negatives (80-82%) • Overall classification <54% correct. • (Barkely et al., 1992; 1994) • Mixed results • Not consistent in identifying group differences

32. Neuropsychological Measures • Wisconsin Card Sorting Task (WCST) • Computerized/manual administration • Participant must correctly sort a series of colored geometric shapes according to an set of rules unknown to the subject. • After each “sort,” the only feedback is correct/incorrect • Rules must be deduced from this feedback • Rules change on each successive trial • Requires an ability to shift attention • (Mirsky et al., 1991; Heaton et al., 1993) • Not recommended for diagnostic use. • False negative 61-89%;

33. MEASURES OF ACTIVITY

34. Measuring Activity Level • Two primary classifications: • Binary Devices – Respond in an “all or nothing” manner when movement exceeds a threshold value • Proportional Devices – Measure motor activity in direct proportion to the magnitude of movement. (Tyron, 1984)

35. Measuring Activity Level Binary Devices • Mercury Switches • Position change sensors • The “wiggle chair” • Not consistent in identifying group differences • Not related to parent hyperactivity ratings • Pedometers • Activated by the impact of the foot & ground • Photoelectric cells

36. Actometers Proportional Devices • Actometers – ankle or wrist • Modified self-winding watches • Movements of the limb corresponds to movement of the watch’s hands • Sensitive to stimulant drug effects • Laboratory actometer ratings not significantly related to parent ratings of hyperactivity at home • Ankle actometers relate to CPT CEs.(.37) • (Barkely et al., 1975; Ullman et al., 1978)

37. Parent Rating Scales

38. Rating Scales • Should address aspects of the following: • core features of ADHD • symptom severity and development • level of impairment • comorbid conditions • Advantages: • Standardized • Decreases subjectivity • Cost-effective method for multiple informants • Can be completed prior to evaluation • Access to infrequently displayed behaviors that may be missed in observation periods • (Anastopoulos 2001)

39. Rating Scales • Potential limitations: • Assume informant is familiar enough with the subject to accurately complete the measure • The informant must be able to understand the questions • Adult psychopathology may distort parent perceptions of the child • Parental or teacher tolerance of behavior may influence ratings. • (Anastopoulos 2001; Sattler 2002)

40. Rating Scales • Conners’ Rating Scales • Parent & Teacher revised versions • Children 3-17 • Parent 80 items (27 on the Short-form) • Teacher 59 items (28 on the Short form) • Short form has limited scales – focus on ADHD/ODD symptoms • Self-report for adolescents 12-17 • Conners-Wells Adolescent Self Rating Scale • 87-item (27 on the short form) • Male & female norms in 3 year intervals • Rating on a 4-point scale

41. Rating Scales • Conners’ Rating Scales • Ratings based on the previous month • Excellent psychometric properties • Simple comparisons between teacher & parent versions • ADHD Index (parent form): 12 items • Hyperactivity Scale moderately related to total hyperactivity score during analogue observation • Barkely 1991

42. Rating Scales • Behavioral Assessment Scale for Children (BASC) • (Reynolds & Kamphaus, 1992) • Parent, teacher, and self ratings scales; Student observation system • Ratings over the previous 3 months • Preschool, child and adolescent versions • 130 items on a 4 point scale (parent & teacher) • 170 True/False items for the self-report form

43. Rating Scales • BASC • Scales include: adaptability, aggression, anxiety, attention problems, atypicality, conduct problems, depression, hyperactivity, leadership, learning problems, social skills, somatization, study skills, & withdrawal • Provides index of Adaptive Skills

44. Rating Scales • BASC • Excellent psychometrics; correlates highly with the CBCL & Conners’; moderately with the PIC. • More predictive of ADHD status than the CBCL • 88% of the sample correctly identified as ADHD (using the Attention subscale) • (Ostrander et al., 1998)

45. Rating Scales • Achenbach Child Behavior Checklist (CBCL) • Recently revised with new normative sample • Parent, teacher, & self-rating form of behaviors over the past 6 months • Externalizing, Internalizing, and Total Problem Scale • Attention & hyperactivity profiles • Perhaps the most frequently used broad-banded measure in research • Anastopoulos & Shelton, 2001)

46. Rating Scales • DSM-IV SNAP-IV ADHD Checklist • (Swanson, 1992) • For parents, teachers, caregivers • DSM-IV symptoms on a 4 point rating scale • Does not include: • rating on impairment in function • information of symptoms across setting • symptom chronicity ratings • symptom onset data

47. Rating Scales • SNAP-IV • Sample items: • Does not seem to listen when spoken to • Often “on the go” or acts as if “driven by a motor” • Often has difficulty waiting for a turn • Research screener for ADHD • Adult version is available

48. Rating Scales • Personality Inventory for Children • 280/420 item parent rating form (True/False) • Lacks an inattentive subscale • Devereux Scales of Mental Disorders • Caregiver rating form • 5 point scale based on the previous month • Only 4 inattention items, 3 impulsivity items & 3 hyperactivity items • No hyperactivity or impulsivity subscale • Modest psychometrics

49. Rating Scales • Behavior Rating Inventory for Executive Function (BRIEF; Gioia et al., 1996) • Designed to assess several aspects of executive functioning • Inhibition, Shift, Emotional Control, Working Memory, Planning/Organization, Organization of materials, Monitoring • For children ages 5-18 • 86 items; Parent & Teacher versions

50. Rating Scales • BRIEF • May help differentiate ADHD subtypes • (Barkely, 1997) • May be useful in identifying difficulites associated with ADHD (e.g. poor behavioral initiation; planning, organization) • Working Memory & Inhibit Scales moderately predictive of ADHD diagnosis (Predominately Inattentive or Combined Type)