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 This paper describes the properties of the PICS, a valid and reliable research instrument in which the source of information is restricted to parents’ direct observations. It is used in parallel with separate instruments capturing observations made in the school situation. The PICS is a semistructured parent interview that uses a naturalistic context for probing into a child’s behaviour in daily living situations; it provides coverage of the full range of symptoms of ADHD, ODD, and CD, in accordance with the criteria of the DSM-IV classification (1). The PICS interview examines symptoms by asking the informant to describe the child’s behaviour in his or her own words in various preselected situations; however, the context and the symptoms probed for in each situation are standardized. Each symptom is probed in one situation reflecting a more structured condition (for example, homework) and in another less structured state (for example, leisure time). Information is restricted to direct observations made by parents, excluding potential distortion emerging from other sources. The clinician conducting the interviews makes a decision about the presence of each symptom and the associated impairment. Detailed information about the instrument and administration manual is available from the authors. MethodThe sample comprised 594 children, aged 6 to 16 years, mean (SD) age 8.67 (1.81) years, with a boy-to-girl ratio of 3.2:1, referred to the outpatient psychiatry clinic of a pediatric hospital and 26 normal control subjects of the same age range (mean [SD] 9.04 [1.63] years), with a boy-to-girl ratio of 1.6:1, recruited from advertisements placed in a hospital staff newsletter. We excluded individuals with IQ scores of less than 80; neurologic dysfunction or poor physical health; sensory impairments, psychosis, pervasive developmental disorders; or chronic tic disorders. The protocol was reviewed and approved by an independent institutional research ethics board. Parents of all subjects gave written consent for their children to participate in the study, and all children gave oral assent. The assessment protocol included information from participant children, their parents, and their classroom teachers. Evaluation of the child consisted of a 6-hour evaluation divided into two, 3-hour sessions with a 1-hour lunch break. We measured the intellectual abilities of the participant children with the WISC-3rd edition (2). We evaluated academic attainment with the WRAT-Revised (3). Inhibitory control was measured with the Stop Signal Task (4), which has been shown to distinguish ADHD-affected and nonaffected populations (4). Participants were medication-free at the time of the evaluation. PICS interviews were conducted and videotaped to evaluate reliability. A standardized TTI (5) was completed within 2 weeks of the clinic visit. We obtained the Conners’ Rating Scales-Revised (6) and the Revised Ontario Child Health Study Scales (7) from parents and teachers. To appraise reliability, 48 randomly selected, videotaped interviews were rescored by an independent reviewer blinded to original ratings. Reliability of diagnoses was assessed with intraclass correlation coefficient analyses and statistics (8). A sensitivity-specificity analysis identified that a T score of 70.5 on the CPRS-ADHD Index optimized agreement between the PICS and CPRS. Convergence between the PICS and CPRS-ADHD Index classification was then assessed with chi-square statistics. Cases meeting PICS criteria for ADHD (PICS positive) and scoring in excess of the CPRS-ADHD Index threshold (CPRS positive), those who were PICS positive but scored below the threshold for the CPRS-ADHD Index (CPRS negative), those who were PICS negative but CPRS positive, and normal control subjects were contrasted with ANOVA-planned comparisons (9). ResultsThe mean (SD) age of the reliability study subsample was 8.83 (1.98) years, range 6 to 13 years;13 of the 48 subjects were girls. Reliability was good for diagnoses of ADHD (k = 0.73) and CD (k = 0.73) and excellent for ODD (k = 0.80). Kappas for individual ADHD symptoms ranged from 0.50 to 0.96; reliability was excellent for 10 of these symptoms, good for 7, and fair for 1. Reliability was either excellent or good for ODD symptoms (range 0.87 to 0.66). Owing to low prevalence, individual CD symptoms could not be evaluated with the kappa statistic. Intraclass correlation coefficients for total symptom scores were as follows: ADHD inattentive = 0.93, ADHD hyperactive-impulsive = 0.97, ODD = 0.96, and CD = 0.86. Agreement between the PICS-ADHD and the CPRS-ADHD Index classification of ADHD was substantial (c2 = 44.7, P < 0.001). Approximately two-thirds of the clinical sample were classified similarly as either “cases” (44.9%, n = 267) or “noncases” (20.2%, n = 120). However, about one-third of cases were discrepant; (32.9 % n = 196). Table 1 compares PICS and CPRS convergent and nonconvergent groups and NCs. No differences were found on measures of intellectual abilities or academic attainment among the ADHD affected groups. However, on the Stop Signal paradigm, greater impairment in inhibitory control was observed in cases identified as ADHD by the PICS, compared with those identified by the CPRS.
DiscussionThe PICS was developed to fill a gap in the available tools for assessing ADHD. We reasoned that, to address situational specificity, there was a need for a semistructured diagnostic instrument that would contain information directly observed by the parent and that would exclude from consideration information obtained second-hand from other informants. The need to distinguish information based on the informant source derives partly from the distinct pattern of ADHD heritability associated with parent, compared with teacher, ratings (10); the generally low agreement between parents and teachers on the nature and severity of observed behaviour; and the relatively weak correlates of parent- and teacher-reported ADHD behaviour (11). Thus, for research purposes, we recommend that a standardized parent interview like the PICS be used in combination with such separate standardized teacher interviews as the TTI (5) or the Child Attention-Deficit Hyperactivity Disorder Teacher Telephone Interview (12), to independently evaluate symptoms present at home and at school. Our study confirmed that the PICS has solid reliability that is in line with available structured and semistructured interviews like the Diagnostic Interview Schedule for Children (13) and the Schedule for Affective Disorders and Schizophrenia for School-Age Children (14), respectively. Although agreement between PICS and CPRS scale classifications was substantial and significant, it was not as high as clinicians might hope. It is not possible to conclude that one instrument was superior to the other; in fact, it may be that each instrument is sensitive to some aspects of the disorder. Nevertheless, the PICS appears to have superiority over a standardized questionnaire in identifying impairments in inhibitory control, one of the cognitive deficits associated with ADHD. NoteInformation about the instrument and administration manual is available from the authors. Public access to the instrument can be found at www.sickkids.ca/psychiatry. Funding and SupportFinancial support was provided by the Canadian Institutes for Health Research. Grant # MOP 64277. AcknowledgementsWe give special thanks to the children and parent participants. We also thank Victoria Orekhovsky, Alison Golob, Susan Parry, and Sharon Nancekivell for their assistance in the preparation of this paper. References1. American Psychiatric Association. Diagnostic and statistical manual of mental disorders. 4th ed. Washington (DC): American Psychiatric Association; 1994. 2. Wechsler D. Wechsler Intelligence Scale for Children. 3rd ed. San Antonio (TX): The Psychological Corporation; 1991. 3. Wilkinson GS. The Wide Range Achievement Test. 3rd ed. Wilmington (DE): Wide Range Inc; 1993. 4. Schachar R, Mota VL, Logan GD, Tannock R, Klim P. Confirmation of an inhibitory control deficit in attention-deficit/hyperactivity disorder. J Abnorm Child Psychol 2000;28:227–35. 5. Tannock R, Hum M, Masellis M, Humphries T, Schachar R. Teacher Telephone Interview. [Unpublished Manuscript, 2000]. Located at The Hospital for Sick Children, Toronto, Ontario. 6. Conners K. Conners’ Rating Scales-Revised, Technical Manual. Toronto: Multi-Health Systems Inc; 1997. 7. Boyle MH, Offord DR, Racine Y, Sanford M, Szatmari P, Fleming JE. Evaluation of the original Ontario Child Health Study scales. Can J Psychiatry 1993;38:397–405. 8. Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:159–74. 9. Keppel G. Design and analysis: a researcher’s handbook. 2nd ed. Englewood Cliffs (NJ): Prentice Hall Inc; 1982. 10. Martin N, Scourfield J, McGuffin P. Observer effects and heritability of childhood attention-deficit hyperactivity disorder symptoms. Br J Psychiatry 2002;180:260–5. 11. Achenbach TM, McConaughy SH, Howell CT. Child/adolescent behavioral and emotional problems: implications of cross-informant correlations for situational specificity. Psychol Bull 1987;101:213–32. 12. Holmes J, Lawson D, Langley K. The Child Attention Deficit Hyperactivity Disorder Teacher Telephone Interview (CHATTI): reliability and validity. Br J Psychiatry 2004;184:74–8. 13. Shaffer D, Fisher P, Lucas CP, Dulcan MK, Schwab-Stone ME. NIMH Diagnostic Interview Schedule for Children-Version IV (NIMH DISC-IV): description, differences from previous versions, and reliability of some common diagnoses. J Am Acad Child Adolesc Psychiatry 2000;39:28–38. 14. Ambrosini PJ. Historical development and present status of the schedule for affective disorders and schizophrenia for school-age children (K-SADS). J Am Acad Child Adolesc Psychiatry 2000;39:49–58. AuthorsManuscript received August 2005, revised, and accepted, December 2005. 1. Staff Psychiatrist, Department of Psychiatry, the Hospital for Sick Children, Toronto, Ontario; Assistant Professor, Department of Psychiatry, University of Toronto, Toronto, Ontario. 2. Director of Psychiatry Research, Brain and Behaviour Programme, Hospital for Sick Children, Toronto, Ontario; Professor of Psychiatry, Department of Psychiatry, University of Toronto, Toronto, Ontario. 3. Social Worker, Department of Psychiatry, the Hospital for Sick Children, Toronto, Ontario; Lecturer, Department of Psychiatry, University of Toronto, Toronto, Ontario. 4. Research Associate, Psychiatry Research, Brain and Behaviour Programme, Hospital for Sick Children, Toronto, Ontario. 5. Social Worker, Department of Psychiatry, the Hospital for Sick Children, Toronto, Ontario. 6. Social Worker, Department of Psychiatry, the Hospital for Sick Children, Toronto, Ontario. Address for correspondence: Dr A Ickowicz, Department of Psychiatry, The Hospital for Sick Children, 555 University Ave, Toronto, ON M5G 1X8 e-mail: abel.ickowicz@sickkids.ca
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