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Keywords:

  • autistic disorder;
  • pervasive developmental disorder not otherwise specified (PDDNOS);
  • preschool;
  • prognosis

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGMENTS
  8. REFERENCES

Abstract  This study is the first to compare the change in developmental quotient (DQ) or IQ between autistic disorder (AD) and pervasive developmental disorder not otherwise specified (PDDNOS) in preschool years. Forty-nine AD children and 77 PDDNOS children were evaluated at age 2 and at age ≥5. The AD children were significantly lower in DQ/IQ at initial evaluation and outcome evaluation (also with initial DQ being controlled for) than the PDDNOS children.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGMENTS
  8. REFERENCES

In a review of epidemiological studies of pervasive developmental disorders (PDD) Fombonne estimated the prevalence for autistic disorder (AD) and pervasive developmental disorder not otherwise specified (PDDNOS) to be 10/10 000 and 15/10 000, respectively.1 It is clear from these figures that children with PDDNOS represent a substantial group whose treatment needs are as important as those of children with AD.

There have already been many prognostic studies for AD, most of which demonstrated that an IQ or developmental level around age 5 was a good predictor of mental development into adulthood.2,3 There are fewer prognostic studies, if any, on PDDNOS. Because the outcome of AD has been researched, comparing PDDNOS with AD in developmental/intellectual ability can shed light on the outcome of PDDNOS.

We have already identified the clinical variables at age 2 that significantly influence developmental quotient (DQ)/IQ at age 5, but intellectual outcomes among PDD subtypes remain to be investigated.4 In the present study we attempted to compare changes in DQ/IQ between AD and PDDNOS in preschool years using relatively large samples.

METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGMENTS
  8. REFERENCES

Because PDDNOS is defined as a residual category of PDD and has no operational criteria,5 we used ICD-10 criteria for atypical autism with atypicality in symptomatology to diagnose PDDNOS.6 In order to reduce heterogeneity in the PDDNOS group, we set a rule that PDDNOS patients should also satisfy the Buitelaar and van der Gaag diagnostic criteria for PDDNOS, which require a total of three or more items from criterion A of DSM-V criteria for autistic disorder, including at least one item from (1) qualitative impairments in social interaction.7

The Kyoto Scale of Psychological Development (K-test) is a widely used developmental test with satisfactory reliability and validity in Japan.8 Among the three subtests in the K-test, the Cognition–Adaptation subtest DQ consisting of items such as block design, puzzle, figure drawing, and nesting cup (hereafter simply called DQ) and Japanese version of the Stanford-Binet (B-test) IQ were reasonably close and highly positively correlated with each other (r = 0.86), suggesting that DQ is usable for B-test IQ in PDD infants.9 Because the B-test is sometimes difficult to administer to PDD preschoolers, the K-test was administered to all subjects at initial evaluation and 46.8% of subjects at outcome evaluation.

The 126 subjects were selected from all PDD children visiting either of two clinics in the Tokyo region, provided that they had received evaluation at both age 2 and at age ≥5. At outcome evaluation H.K. diagnosed 49 AD children (mean age at initial evaluation, 31.7 ± 3.3 months; mean age at outcome evaluation, 65.5 ± 5.0 months; 39 male) and 77 PDDNOS children (mean age at initial evaluation, 31.2 ± 3.3 months; mean age at outcome evaluation, 66.8 ± 7.0 months; 63 male). Three children diagnosed as having PDDNOS at initial evaluation had their diagnoses switched to AD before age 5. There was no significant difference in mean age at initial and outcome evaluation, or in sex ratio between the two groups.

The AD group (mean score at initial evaluation, 34.8 ± 3.5; mean score at outcome evaluation, 33.4 ±3.7) recorded significantly higher total scores on the Childhood Autism Rating Scale-Tokyo Version10 than the PDDNOS group (mean score at initial evaluation, 31.4 ± 2.8; mean score at outcome evaluation, 29.0 ±5.0) at both initial and outcome evaluation.

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGMENTS
  8. REFERENCES

Figure 1 shows DQ/IQ at ages 2 and 5 in AD and PDDNOS groups. At age 2 the AD group had a mean DQ score of 59.0 ± 12.3, compared with 65.2 ± 16.1 for the PDDNOS group, and at age 5 the AD group had a mean DQ/IQ score of 52.0 ± 19.9, compared with 66.4 ± 27.4 for the PDDNOS group. In ancova with initial DQ as covariate, the DQ/IQ at outcome evaluation was still significantly higher in PDDNOS than AD (F1,123 = 4.6, P = 0.034). There were significant negative correlations between Childhood Autism Rating Scale–Tokyo version score and DQ/IQ at both points of time in both groups with 1% significance, except in PDDNOS at age 2 (AD at age 2, r = −0.67, AD at age 5, r = −0.68; PDDNOS at age 2, r = −0.36, PDDNOS at age 5, r = −0.82).

image

Figure 1. Mean DQ/IQ at ages 2 and 5 in (▪) autistic disorder and (●) pervasive developmental disorder not otherwise specified.

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DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGMENTS
  8. REFERENCES

The PDDNOS children had a higher DQ/IQ score than AD children at both initial and outcome evaluation and the difference in change in DQ/IQ over time between the two groups was significant. Considering the results of previous prognostic studies,2–4 we conclude that DQ at age 2 plays a crucial role in predicting later intellectual development in PDD, and that PDDNOS children have a relatively better adulthood intellectual outcome than AD children. These findings seem important in supporting and helping PDD children and their families.

A few limitations in the present study need to be addressed. The fact that diagnoses at age 5 relied on clinical assessment by a clinician who was not blind to the diagnoses at age 2 rather than on structured diagnostic instruments by a clinician who is blind to the diagnoses at age 2 might influence the accuracy in diagnoses. In the present study DQ at age 5 was regarded as IQ in some cases, but DQ is different from IQ in concept. Moreover, because the PDDNOS group consisted of heterogeneous cases in symptomatology, dividing it into several subgroups according to symptoms and then comparing them in terms of a prognosis would be of considerable clinical use. A further study with more rigorous methodology is needed.

ACKNOWLEDGMENTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGMENTS
  8. REFERENCES

We thank Mr Jyunichi Yukimoto and Ms Mika Tobari for their help in data collection.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGMENTS
  8. REFERENCES
  • 1
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  • 2
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    American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 4th edn. American Psychiatric Association, Washington, DC, 1994.
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    Buitelaar JK, Van Der Gaag RJ. Diagnostic rules for children with PDD-NOS and multiple complex developmental disorders. J. Child Psychol. Psychiatry 1998; 39: 911919.
  • 8
    Ikuzawa M, Matsushita Y, Nakase A, Shimazu H. Kyoto Scale of Psychological Development. Nakanishiya, Kyoto, 1985.
  • 9
    Koyama T, Osada H, Tachimori H et al. Clinical significance of developmental quotient in developmental assessment of children with pervasive developmental disorders. Jpn J. Clin. Psychiatry 2003; 32: 10811087 (in Japanese).
  • 10
    Kurita H, Miyake Y, Katsuno K. Reliability and validity of the Childhood Autism Rating Scale–Tokyo Version. J. Autism Dev. Disord. 1989; 19: 389396.