IN 2003, AN UPDATED version of the Wechsler

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1 Psychiatry and Clinical Neurosciences 2013; 67: doi: /pcn Regular Article Wechsler Intelligence Scale for Children 4th edition-chinese version index scores in Taiwanese children with attention-deficit/hyperactivity disorder Pinchen Yang, MD, 1 Chung-Ping Cheng, PhD, 5 Chen-Lin Chang, MD, 2,4 Tai-Ling Liu, MD, 1 Hsiu-Yi Hsu, MS 3 and Cheng-Fang Yen, MD, PhD 1 * 1 Department of Psychiatry, 2 Graduate Institute of Medicine, 3 Department of Pediatrics, Faculty of Medicine, College of Medicine, Kaohsiung Medical University & Kaohsiung Medical University Hospital, 4 Department of Psychiatry, Kaohsiung Armed Forces General Hospital, Kaohsiung and 5 Department of Psychology, National Cheng Kung University, Tainan, Taiwan Aim: The Wechsler Intelligence Scale for Children 4th edition-chinese version (WISC-IV-Chinese) has been in clinical use in Taiwan since Research is needed to determine how the WISC-IV, modified from its earlier version, will affect its interpretation in clinical practice in a Mandarin-speaking context. Methods: We attempted to use WISC-IV-Chinese scores to identify the cognitive strengths and weaknesses in 334 Taiwanese children with attentiondeficit/hyperactivity disorder (ADHD). Comparison of cognitive profiles of WISC-IV-Chinese scores between subtypes of ADHD was also performed. Results: The results indicated that the four-factor model of the WISC-IV-Chinese fitted well for Taiwanese children with ADHD. The profiles showed that performance in the index score of the Processing Speed Index was the weakness domain for the Taiwanese children with ADHD, as confirmed by two different kinds of analytic methods. Cognitive profile analysis of ADHD subtypes revealed children with inattentive subtypes to have a greater weakness in processing speed performance. Conclusion: The implications of the profiles of the index scores on the WISC-IV-Chinese version for Taiwanese children with ADHD were explored. Key words: attention-deficit/hyperactivity disorder, cognition, psychometrics. IN 2003, AN UPDATED version of the Wechsler Intelligence Scale for Children, known as the Wechsler Intelligence Scale for Children Fourth Edition (WISC-IV), 1 was published and put into clinical usage in English-speaking countries. The WISC-IV is a psychometric measure of intelligence for children aged 6 16 years. The WISC-IV differs from its previous version, the WISC-III, 2 in significant ways. In *Correspondence: Cheng-Fang Yen, Department of Psychiatry, Faculty of Medicine, College of Medicine, Kaohsiung Medical University & Department of Psychiatry, Kaohsiung Medical University Hospital, 100 Shi-chuan 1st Rd, Kaohsiung 807, Taiwan. p @gmail.com Received 4 July 2012; revised 3 November 2012; accepted 27 November essence, there is a move away from a verbal performance dichotomy of intellectual abilities, and all four of the index scores are included in the calculation of full-scale IQ (FSIQ). The psychometric properties of the English WISC-IV are strong 3 but revisions made to the WISC-III when developing the WISC-IV may have altered previously identified patterns of subtest and index score performance in clinical populations. For example, studies of children with traumatic brain injury have shown profile differences when comparing the WISC-IV to older versions of the WISC-III. 4 Western studies on the data obtained from WISC- III of specific clinical groups have reported some distinct and reliable subtest and index profiles in childhood neurodevelopmental disorders, such as 83

2 84 P. Yang et al. Psychiatry and Clinical Neurosciences 2013; 67: autism 5,6 and attention-deficit/hyperactivity disorder (ADHD). 7 A commonly reported Wechsler profile among school-aged children with ADHD includes lower score on the Freedom From Distractibility (FFD) Index (replaced by the Working Memory Index on the WISC-IV) and the Processing Speed Index (PSI) as compared with other indexes As for data obtained from WISC-IV, there has been preliminary data on the subtest patterns of ADHD reported in the English WISC-IV manual. 1 Also, Mayes et al. 13 have examined the profile differences between the WISC- III and WISC-IV and the results showed that all children in the WISC-IV sample scored lowest on Working Memory Index (WMI) or PSI, whereas only 88% of the WISC-III children scored lowest on FFD or PSI. In addition, the index discrepancies were greater for the WISC-IV, suggesting that the WISC-IV might be better than the WISC-III in delineating the strengths and weaknesses of children with ADHD. Furthermore, prior studies have demonstrated an association between ADHD symptoms and weaknesses in both working memory 15 and processing speed. 16 Using hierarchical cluster analysis Thaler et al. 17 found a relation between reduced processing speed in WISC-IV and inattention in a sample of ADHD children. The WISC-IV has been in clinical use in Taiwan since 2007, when the translation and standardization were completed. 18 During the standardization of the WISC-IV-Chinese version in this Mandarin-speaking population, data were drawn from 968 samples, but not collected specifically from clinical subjects. Even though there has been literature published discussing the validity of the four-factor scoring structure of the WISC-IV-Chinese and the Cattell-Horn-Carroll theory-based interpretative approach, 19 there has been no previous report, to the best of our knowledge, on the application of the WISC-IV-Chinese in clinical populations in Mandarin-speaking contexts. With this in mind, the current study was designed to examine WISC-IV-Chinese performance in 338 children with ADHD using two different profile analytic approaches. The goal was to examine whether the profiles of the WISC-IV-Chinese index scores of the Mandarin-speaking ADHD was similar to that of ADHD children in English-speaking countries. In addition, we wanted to inspect whether cognitive profile can contribute to the clinical subtyping of the heterogeneous ADHD. The rationale for this is that it has been shown that children diagnosed with Predominantly Inattentive (ADHD-I) and Combined subtypes of ADHD (ADHD-C) differ in cognitive tempo, age of onset, sex ratio, and comorbidity, yet a differentiating endophenotype has not been unequivocally identified. Solanto et al. 7 have evaluated children with subtypes of ADHD-C, ADHD-I and normal control by WISC-III and neuropsychological tests battery. They found children diagnosed with the ADHD-I showed worse performance than the ADHD-C and control groups on the PSI of WISC- III. However, there was no support in the data for hypothesized differences between subtypes in specific functioning of the brain systems, nor in involvement of processes as revealed by neuropsychological tests. In this current survey, we also wanted to examine whether there was difference between the subtypes in cognitive performance that can be revealed by the WISC-IV-Chinese version. METHOD Subjects The ADHD subjects were 6 12-year-old children recruited from the outpatient service of the Department of Psychiatry of Kaohsiung Medical University Hospital, Taiwan who met the following criteria: (i) a diagnosis of ADHD by child psychiatrists on the basis of DSM-IV-TR 20 criteria; (ii) a child at the initial stage of assessment and medication-naïve; (iii) a child who did not have comorbid mental retardation and autism spectrum disorder; and (iv) a child who did not have any known associated or causative genetic, metabolic, or infectious conditions, and had no history of seizures, birth injury, or head trauma. The diagnosis of ADHD was made through the application of multiple data sources, including (i) a clinician s interview; (ii) clinical observation of the subject s behavior; and (iii) a history provided by the parents and the Chinese version of the Swanson, Nolan and Pelham IV scales. 21 Data were collected as part of the clinical evaluation in the outpatient service. Of the children evaluated in our clinic during the 14-month recruitment period (September 2010 to October 2011), 338 were eligible according to the above criteria. In all, 334 children underwent WISC-IV-Chinese assessment with no missing data and these 334 subjects entered analysis. Subtype information for each child was extracted from hospital notes. The majority were boys (male/female: 281/53) and the age range was

3 Psychiatry and Clinical Neurosciences 2013; 67: WISC-IV-Chinese and ADHD years old. Regarding diagnostic subtypes, 207 children were diagnosed as having ADHD-C and 127 children as having ADHD-I. No children were diagnosed as having hyperactiveimpulsive subtype in this cohort. This study was approved by the Institutional Review Board of Kaohsiung Medical University Hospital. Informed consent was obtained from the subjects parents, in accordance with the guidelines of the Institutional Committee on Clinical Investigation. MEASURES WISC-IV-Chinese The WISC-IV-Chinese is an individually administered and norm-referenced instrument designed to measure intelligence. 18 The WISC-IV contains 10 core subtests and five additional subtests. These are summed into a four-index score and one FSIQ, which ranges from the lowest (40) to the highest (160) points. Regarding the four index scores, the Verbal Comprehension Index (VCI) includes the Vocabulary, Similarities, and Comprehension subtests; the Perceptual Reasoning Index (PRI) includes the Block Design, Picture Concepts, and Matrix Reasoning subtests; the WMI includes the Digit Span and Letter Number Sequencing subtests; and the PSI includes the Coding and Symbol Search subtests. Index standard scores have a mean of 100 and an SD of 15. All the tests were performed by clinical psychologists. Statistical analysis Means and SD for IQ index scores and subtest scores were reported for the ADHD subjects. The adequacy of the four-factor structure of the WISC-IV-Chinese for use with Taiwanese children with ADHD was examined using confirmatory factor analysis (CFA). The distributions of items were not normal, therefore, maximum likelihood method with Satorrae Bentler correction for non-normality was used to estimate parameter and calculated goodness-of-fit indices. Four goodness-of-fit indices, including the root mean square error of approximation (RMSEA), standardized root mean square residual (SRMR), non-normal fit index (NNFI), and comparative fit index (CFI) were recommended. RMSEA values > 0.10 are typically considered poor and values <0.10 are acceptable. An SRMR < 0.08, NNFI > 0.90, and CFI > 0.90 indicate a good fit. We did not recruit a control group, so the significance of differences between obtained standard scores and the normal mean of 100 was determined with z scores. For the profile analysis we first examined the significance of differences between pairs of test scores within the WISC-IV groups by conducting repeated-measure ANOVA, in which index scores were the dependent variables, with subsequent contrast effects being performed to compare individual indices. Because PSI was identified as the weakness domain from the above analysis, we further analyzed PSI and its respective subtests (Coding and Symbol Search) relative to other WISC-IV scores in the total sample. In addition, for further analysis of subtype differences, three discrepancy scores were calculated to represent each child s Processing Speed performance relative to other WISC-IV scores: (i) FSIQ minus PSI (IQ PSI); (ii) IQ minus Coding (IQ Coding); and (iii) IQ minus Symbol Search (IQ Symbol Search). Coding and Symbol Search scores were converted into standard scores with a mean of 100 and an SD of 15 so that all test scores were comparable. Independent t-test was calculated to investigate the significance of differences between pairs of test scores between the two ADHD subtypes. Bonferroni corrections were utilized for correction of the errors of multiple comparisons. Bonferroni correction (P < 0.05) for the four-index score is P < 0.01 and for the 10 subtest score comparison is P < All tests of significance were two-tailed. Then, we used another analytic method, known as the ipsative comparison, 22 to investigate the profile pattern within the four index scores. The ipsative values were computed utilizing Davis s formula for the difference between the average of several scores obtained by one individual and each of his or her scores included in the average. 23 Silverstein s modification 24 of this procedure was applied to correct the z value used to compute the differences needed for significance based on the number of comparisons made to the mean. We followed the required steps to decide the ipsative values as reported and detailed in table 1 of the report by Naglieri et al. 22 This table provided the differences required for significance, at the 0.05 and 0.01 levels, when comparing each WISC-IV scale standard score to the mean of the four standard scores. These values, based on making four simultaneous comparisons to the mean, differ across chronological age, and they also differ as a function of the reliability of each scale. The four required steps are as follows.

4 86 P. Yang et al. Psychiatry and Clinical Neurosciences 2013; 67: Calculate the average of the four obtained WISC-IV scale standard scores. 2 Subtract this mean from each of the individual Index scores to obtain a deviation score. 3 Reference Naglieri s table 1 22 to obtain the values corresponding to the child s chronological age and level of significance desired to obtain the difference needed for significance (set at 0.05 in our current study). 4 If the deviation score is equal to or greater than the value found in the table, then the variation is significant; positive significant values should be considered as strengths, and negative values as weaknesses. The percentages of ADHD children whose index scores were strengths or weaknesses were reported as our results. Finally, we used c 2 -test to determine which index score was the most frequently reported weakness among the ADHD children. RESULTS For the total sample of 334 children, the means of all four indexes were significantly below the normal mean of 100 (VCI z = 8.40, PRI z = 5.00, WMI z = 5.83, PSI z = 9.91, P ). The total sample and two subtype profiles are reported in Table 1. There was no difference between the two subtypes of children (ADHD-C and ADHD-I) in terms of index scores and subtest scores using the Bonferroni correction (to control for the number of comparisons made). The results of using CFA to examine the adequacy of the four-factor structure of the WISC-IV-Chinese indicated that the values of all indices met our goodness-of-fit standards (c 2 =50.47, P = 0.008, RMSEA = 0.048, SRMR = 0.038, NNFI = 0.98, CFI = 0.99). The results indicated that the four-factor model of the WISC-IV-Chinese fitted well for Taiwanese children with ADHD. Standardized factor loadings of the four-factor model of the WISC-IV are shown in Table 2. As for profile pattern analysis, the index score differences among the ADHD children using repeatedmeasure ANOVA were as follows: for the whole group, index scores of PSI/VCI were the weaknesses; for ADHD-I, PSI/WMI were the weaknesses; while for ADHD-C, PSI/VCI were the weaknesses. The detailed Table 1. Descriptive statistics for the WISC-IV Subtest and Index scores in 334 children with ADHD WISC-IV scores Total ADHD n = 334 ADHD-C n = 207 ADHD-I n = 127 Index Verbal Comprehension 93.1 (12.0) 91.9 (11.8) 95.1 (12.2) Perceptual Reasoning 95.9 (14.6) 94.5 (13.5) 98.2 (16.0) Working Memory 95.2 (12.5) 95.6 (12.8) 94.6 (12.1) Processing Speed 91.9 (15.6) 92.1 (16.4) 91.4 (14.3) Full-scale IQ 92.3 (13.0) 91.6 (12.8) 93.5 (13.2) Subtest Similarities 9.1 (3.2) 8.9 (3.2) 9.4 (3.0) Vocabulary 9.0 (2.7) 8.7 (2.6) 9.4 (2.8) Comprehension 8.6 (2.4) 8.4 (2.5) 8.9 (2.2) Block Design 10.2 (2.8) 10.1 (2.8) 10.4 (3.0) Picture Concepts 8.7 (3.2) 8.4 (3.1) 9.2 (3.3) Matrix Reasoning 9.2 (2.9) 8.9 (2.8) 9.5 (3.0) Digit Span 9.3 (2.6) 9.4 (2.6) 9.3 (2.6) Letter Number Sequencing 9.0 (2.8) 9.1 (2.7) 8.8 (2.8) Coding 8.4 (3.5) 8.4 (3.6) 8.4 (3.3) Symbol Search 8.8 (3.0) 9.0 (2.9) 8.5 (3.1) There was no significant difference in Index and Subtest scores between ADHD-C and ADHD-I groups. Bonferroni correction (P < 0.05) for the four index score comparisons is P < 0.01 and for the 10 subtest score comparisons it is P < ADHD, attention-deficit/hyperactivity disorder; ADHD-C, ADHD-Combined Subtype; ADHD-I, ADHD-Inattentive Subtype; WISC-IV, Wechsler Intelligence Scale for Children-Fourth Edition.

5 Psychiatry and Clinical Neurosciences 2013; 67: WISC-IV-Chinese and ADHD 87 Table 2. Standardized factor loadings and correlations between four-factor model of the WISC-IV in Taiwanese children with ADHD VCI PRI WMI PSI Vocabulary Similarity Comprehension Block Design Picture Concepts Matrix Reasoning Digit Span Letter Number Sequencing Coding Symbol Search VCI PRI WMI PSI ADHD, attention-deficit/hyperactivity disorder; PRI, Perceptual Reasoning Index; PSI, Processing Speed Index; VCI, Verbal Comprehension Index; WISC-IV, Wechsler Intelligence Scale for Children, Fourth Edition; WMI, Working Memory Index. descriptions were reported as below and summarized in Table 3. For all 334 ADHD children, the repeated measures ANOVA examining potential differences between the four index scores was significant (F(3,999) = 10.40, P 0.001). Contrasts indicated that there were no significant differences among the VCI and PSI, but significant differences were present between the PRI and VCI, P = 0.001, and the PSI, P < 0.001; and between the WMI and VCI, P = 0.013, and the PSI, P = For the 127 children with ADHD-I, the repeated measures ANOVA examining potential differences between the four index scores was also significant (F(3,378) = 8.54, P < 0.001). Contrasts indicated that significant differences were present between the PRI and WMI (P = 0.023); and the PSI (P < 0.001). For the 207 children with ADHD-C, the repeated measure ANOVA was also significant (F(3,618) = 6.29, P < 0.001). Contrasts indicated that there were no significant differences among the VCI and PSI, but significant differences were present between the PRI and VCI (P = 0.014), and between the WMI and VCI (P < 0.001), and the PSI (P = 0.023). For all tests, the alpha level was set at P = Table 3. Profile analysis of WISC-IV-Chinese for Taiwanese children with ADHD VCI PRI WMI PSI Total n = 334 VCI PRI D = 2.8*, P = D = 4, P < WMI D = 2.1, P = D = 3.4, P = PSI Summary: WMI > PSI/VCI, PRI > PSI/VCI ADHD-C N = 207 VCI PRI D = 2.6, P = WMI D = 3.7, P < D = 3.4, P = PSI Summary: PRI > VCI, WMI > VCI/PSI ADHD-I N = 127 VCI PRI D = 3.6, P = D = 6.7, P < WMI PSI Summary: PRI > WMI, PRI > PSI Value indicates differences of intersecting row value column value. Only positive differences with statistical significance are shown, e.g. *indicates PRI-VCI. D, difference; PRI, Perceptual Reasoning Index; PSI, Processing Speed Index; VCI, Verbal Comprehension Index; WISC-IV, Wechsler Intelligence Scale for Children, Fourth Edition; WMI, Working Memory Index.

6 88 P. Yang et al. Psychiatry and Clinical Neurosciences 2013; 67: Table 4. Percentage of children showing strengths or weaknesses in WISC-IV profile by ipsative comparison Strength in Weakness in Total ADHD n = 334 ADHD-C n = 207 ADHD-I n = 127 VCI PRI WMI PSI VCI PRI WMI PSI 12.6% 15.9% 13.2% 11.7% 14.4% 6.3% 9.0% 20.4% 10.1% 12.6% 15.9% 12.1% 14.5% 7.2% 7.2% 16.4% 16.5% 21.3% 8.7% 11.0% 14.2% 4.7% 11.8% 26.8% ADHD, attention-deficit/hyperactivity disorder; ADHD-C, ADHD-Combined Subtype; ADHD-I, ADHD-Inattentive Subtype; PRI, Perceptual Reasoning Index; PSI, Processing Speed Index; VCI, Verbal Comprehension Index; WISC-IV, Wechsler Intelligence Scale for Children, Fourth Edition; WMI, Working Memory Index. The results for the ipsative comparison are summarized in Table 4. Among the 334 children with ADHD, various percentages of children had individual index scores that were either strengths or weaknesses; however, PSI stood out as the most frequently reported weakness among the four index scores, using ipsative analysis (for total ADHD: 20.4%; for ADHD-C: 16.4%; for ADHD-I: 26.8%). c 2 analysis revealed that for the whole group of ADHD children, PSI was significantly more frequently a weakness in the profile (percentage of VCI as the weakness < percentage of PSI as the weakness, P = 0.031). As for inspection of the PSI index, both Coding (mean = 92) and Symbol Search (mean = 94) were significantly lower than the normal mean of 100 (z =-9.9 and -7.2, P < ) for the total sample; however, Coding was not significantly lower than Symbol Search using Bonferroni correction for the total sample. Subtype comparison on the processing speed discrepancy index revealed that children with ADHD-I had a greater weakness in processing speed performance (FSIQ-Symbol Search discrepancy score) than children with ADHD-C, t(331) = 3.1, P = DISCUSSION Establishing a cognitive profile of children with ADHD based on standard cognitive tests may achieve several objectives. One of them is to examine whether a particular profile on the WISC may help diagnose ADHD. Another objective of conducting a profile analysis is to check whether IQ subtests or index scores may help to determine cognitive strengths and weaknesses in children with ADHD. In our current study, results indicated that the four-factor model of the WISC-IV-Chinese fitted well for Taiwanese children with ADHD. In addition, different methods of pattern analysis showed similar findings of the index score of PSI to be the weakness domain in Taiwanese children with ADHD. Our findings were, in the main, consistent with those of previous Western reports, though details require further discussion. Most of the previous Western studies have reported that both PSI and WMI index were among the weakness domains in children of ADHD; however, we do not replicate this finding. At this stage, we cannot fully explain the reasons why our patterns of WMI scores and those of Western reports differ, but we postulate this to be related to the novel nature of some of the WISC-IV index scores and the different ways of administration of certain subtests in cultural adaptation and translation of this assessment tool. For example, the Working Memory Index in the English WISC-IV is specially assessed through changes made to the Digit Span subtest and the addition of a new subtest, Letter Number Sequencing. In the Letter Number Sequencing subtest, the child listens to sequences of random letters and digits and repeats the digits in numerical order and then the letters in alphabetical order. In contrast to Digit Span and Arithmetic on the FFD Index of WISC-III (which replaces WMI), the Arithmetic subtest now becomes the optional test, which was substituted for Letter Number Sequencing when the latter was invalidated or if the examiner deemed Arithmetic a preferable substitute. 26

7 Psychiatry and Clinical Neurosciences 2013; 67: WISC-IV-Chinese and ADHD 89 Nevertheless, in the Mandarin-Chinese system, there is no corresponding alphabetical symbols system that comes in a fixed order that is familiar to every child. Instead, Chinese is a morphosyllabic language in which each character, the primary unit of writing, represents both a syllable and a lexical morpheme. A character and its components (strokes or radicals) do not represent phonemes. During the Chinese translation of WISC-IV, the authors chose the 12-animal zodiac system (i.e. mouse, ox, tiger, rabbit, dragon, snake, horse, sheep, monkey, rooster, dog, pig) as the Letter part of the Letter Number Sequence subtest; however, the 12-animal zodiac system originating from folk stories is unfamiliar to many young children, especially in clinical sample. In our total sample of 334 children, only 167 of them can be tested by the Letter Number Sequencing subtest, and more than half of them (171) had to use the Arithmetic subtest as substitute for the derivation of the WMI. As reported in the Wechsler Technical and Interpretative Manual, 26 there is a relatively lower correlation between Arithmetic and WMI (r = 0.57) when compared to the correlation between Letter Number Sequencing and WMI (r = 0.86). The cognitive demands between the Arithmetic and Letter Number Sequencing subtests might differ and be confounded by mathematical abilities. The Technical Report of the WISC-IV 26 has emphasized that both the lineage and the newest of the Working Memory and Processing Speed factors require restricted interpretation until ample experimental research on the validity of the new scale labels is available. Nevertheless, the validity of a particular interpretation of scale variability, and especially the hypothetical constructs being assessed, are experimental questions separate from the statistical analysis of group data. We found the PSI index score to be significantly lower than the FSIQ, which is in line with previous Western studies. 8 10,12 The PSI was first introduced on the WISC-III and was primarily visuomotor. Previous data indicate that PSI is more independent of IQ than the other factors in the Wechsler series; 3 however PSI also had lower reliability than the other index coefficients. 2 Because PSI is relatively unique, this factor may have clinical significance for individual children and diagnostic groups. Children with ADHD have been shown to demonstrate slowed processing speed relative to typically developing peers in graphomotor speed, as measured by WISC-IV Processing Speed subtests. 14,25 On the WISC-IV, PSI consists of Coding and Symbol Search as on the WISC-III. Coding measures writing speed while Symbol Search is related to visual mental speed; however, it remains unclear to what extent the slowed performance in children with ADHD is a function of slow motor control, rather than slowed information processing at the level of response selection and preparation, prior to execution of the motor response. In our data, we also found both the Coding and Symbol Search subtest to be lower than the population mean of 100; also, the ADHD-I subgroup can be demonstrated to have processing speed performance problems in the PSI discrepancy scale. These findings all implied that we should look for performance speed weaknesses of the children with ADHD in the real world function. While low PSI scores by themselves do not predict clinical diagnoses, the identification of weaknesses in these areas is helpful in understanding the neuropsychological profiles of these children and may have important implications for educational intervention (i.e. the need to remediate, compensate for, and circumvent the attention, writing, and performance speed weaknesses). From our data we may conclude that in the case of Taiwanese children with ADHD, attending to the weakness in performance speed is probably the first thing adults need to consider in attempting to improve the child s daily function. Clinicians should ensure that these areas are properly assessed and that intervention is provided. For example, homework assignment with repetitive writing practice should be avoided. As reported in our data obtained from the ipsative comparison, 14.4% of the children in our sample were found to score lowest on VCI, 6.3% scored lowest on PRI, 9.0% scored lowest on WMI, and 20.4% scored lowest on PRI. In essence, even though the index of PRI was found statistically to be the most frequent weakness domain in Chinese-speaking children with ADHD, not all children scored lowest on any particular index score. There seemed to be plenty of individual differences. Our data showed that ADHD-C and ADHD-I subtypes differed in processing speed performance as noted from processing speed discrepancy scores. Given that we only arranged general intelligence tests without concomitant neuropsychological assessments, this finding can only provide limited information in the field of ADHD subtyping. Our data corroborates previous Western findings; 16,17 however, there is still inadequate support for using the

8 90 P. Yang et al. Psychiatry and Clinical Neurosciences 2013; 67: cognitive assessment data for subtyping ADHD, and for the claim about different involvement of brain processes. 26 There were several limitations of this study. First, we relied on a convenience sample that was referred to a single hospital for disorder evaluation. The methodology employed here advantageously provided a direct link between clinical practice and WISC-IV test score interpretation in ADHD; however, a single institution does not have a sufficient number of patients to control for the numerous family-specific and regionspecific variables involved. Second, a finding of significant variation in strengths and weaknesses revealed by statistical methods is only indicative of a reliable difference. Third, the sample was without the condition of mental retardation by inclusion criteria, so the results may not be applicable to children whose FSIQ are below 70. Fourth, we used the report by Naglieri et al. 22 on values of difference for significance in conducting our ipsative comparison and these data were derived from US samples. In the WISC-IV- Chinese Administration and Scoring Manual, 18 values are provided for comparing all possible pair-wise combinations of the four index scales, but values for ipsative approach when psychologists want to determine whether any of the combination of the index scores are significantly different are absent; however, the available Chinese pair-wise comparison values 18 are similar to the US ones published in the English WISC-IV Manual. 1 We hope the similarities will lessen the doubt in our taking advantage of the Western data in conducting an ipsative approach but we do acknowledge this limitation in methodology. In conclusion, the current study examined the WISC-IV-Chinese IQ profile of school-aged Taiwanese children with ADHD. We replicated some of the previous Western works by documenting the PSI as the weakness in ADHD. It is believed that profile analysis at the subtest level with supporting data will be useful in understanding a child s strengths and weaknesses and in guiding treatment and educational programming. ACKNOWLEDGMENT The authors appreciate the help from the Statistical Analysis Laboratory, Department of Medical Research, Kaohsiung Medical University Hospital, Kaohsiung Medical University. The authors declare no conflict of interests. REFERENCES 1. Wechsler D. Wechsler Intelligence Scale for Children-Fourth Edition. Psychological Corporation, San Antonio, TX, Wechsler D. Manual for the Wechsler Intelligence Scale for Children, 3rd edn. Psychological Corporation, New York, Williams PE, Weiss LG, Rolfhus E. The Wechsler Intelligence Scale for Children Fourth Edition. Theoretical Model and Test Blueprint: Technical Report #1. The Psychological Corporation, San Antonio, TX, Donders J, Janke K. Criterion validity of the Wechsler Intelligence Scale for Children-Fourth Edition after pediatric traumatic brain injury. J. Int. Neuropsychol. Soc. 2008; 14: Asarnow RF, Tanguay PE, Bott L, Freeman BJ. Patterns of intellectual functioning in non-retarded autistic and schizophrenic children. J. Child Psychol. Psychiatry 1987; 28: Goldstein G, Allen DN, Minshew NJ et al. The structure of intelligence in children and adults with high functioning autism. Neuropsychology 2008; 22: Solanto MV, Gilbert SN, Raj A et al. Neurocognitive functioning in AD/HD, predominantly inattentive and combined subtypes. J. Abnorm. Child Psychol. 2007; 35: Nyden A, Billstedt E, Hjelmquist E, Gillberg C. Neurocognitive stability in Asperger syndrome, ADHD, and reading and writing disorder: A pilot study. Dev. Med. Child Neurol. 2001; 43: Prifitera A, Dersh J. Base rates of WISC-III diagnostic subtest patterns among normal, learning-disabled, and ADHD samples. In: Bracken BA, McCallum RS (eds). Wechsler Intelligence Scale for Children Third Edition Journal of Psychoeducational Assessment Advances in Psychoeducational Assessment. Clinical Psychology Publishing Co, Brandon, 1993; Schwean VL, Saklofske DH, Yackulic RA, Quinn D. WISC- III performance of ADHD children. J. Psychoeduc. Assess. 1993; 11: Snow JB, Sapp GL. WISC-III subtest patterns of ADHD and normal samples. Psychol. Rep. 2000; 87: Mayes SD, Calhoun SL. Analysis of WISC-III, Stanford- Binet:IV, and academic achievement test scores in children with autism. J. Autism Dev. Disord. 2003; 33: Mayes SD, Calhoun SL. WISC-IV and WISC-III profiles in children with ADHD. J. Atten. Disord. 2006; 9: Calhoun SL, Mayes SD. Processing speed in children with clinical disorders. Psychol. Sch. 2005; 42: Tillman C, Eninger L, Forssman L, Bohlin G. The relation between working memory components and ADHD symptoms from a developmental perspective. Dev. Neuropsychol. 2011; 36:

9 Psychiatry and Clinical Neurosciences 2013; 67: WISC-IV-Chinese and ADHD Chhabildas N, Pennington BF, Willcutt EG. A comparison of the neuropsychological profiles of the DSM-IV subtypes of ADHD. J. Abnorm. Child Psychol. 2001; 29: Thaler NS, Bello DT, Etcoff LM. WISC-IV profiles are associated with differences in symptomatology and outcome in children with ADHD. J. Atten. Disord doi: / Wechsler D. Wechsler Intelligence Scale for Children-Fourth Edition-Chinese Version. The Chinese Behavioral Science Coporation, Taipei, Chen H, Keith TZ, Chen Y, Chang B. What does the WISC-IV measure? Validation of the scoring and CHCbased interpretative approaches. J. Res. Educ. Sci. 2009; 54: American Psychiatric Association. Diagnosis and Statistical Manual of Mental Disorders, 4th edn. Text Revision. American Psychiatric Association, Washington DC, Gau SS, Shang CY, Liu SK et al. Psychometric properties of the Chinese version of the Swanson, Nolan, and Pelham, version IV scale parent form. Int. J. Methods Psychiatr. Res. 2008; 17: Naglieri JA, Paolitto AW. Ipsative comparisons of WISC-IV index scores. Appl. Neuropsychol. 2005; 12: Davis FB. Interpretation of differences among average and individual test scores. J. Educ. Psychol. 1959; 50: Silverstein AB. Pattern analysis as simultaneous statistical inference. J. Consult. Clin. Psychol. 1982; 50: Wechsler D. Wechsler Intelligence Scale for Children Fourth Edition: Techninical and Interpretive Manual. Psychological Corporation, San Antonio, TX, Wodka EL, Mostofsky SH, Prahme C et al. Process examination of executive function in ADHD: sex and subtype effects. Clin. Neuropsychol. 2008; 22: