Pervasive Developmental Disorders is the umbrella term for neuro-developmental disorder exhibited in children which is characterized by language deficits, impaired social skills and abnormal behavior. PDDs include PDD-Not Otherwise Specified (PDD-NOS), Asperger Syndrome, Autism-, Chidhood Disintegrative-, and Rett Disorder. Increase patterns of autism disorders for the past 15 yrs at England may indicate changes in PDD and the study attempted PPD estimation in a defined geographic region.
Population under case study were obtained from child center developments Stafford, Cannock, and Wightwick in the Midlands, England from July 1998 to June 1999 with a target population of 15, 500 children born on and between January 1, 1992, to December 31, 1995, that were identified as residents for the specified area on June 6, 1998.
Case identification for the disease proceeded by four consecutive stages. Stage 1 was primarily concerned with screening by health practitioners and/or pediatricians at 0 wk, 6 wk, 6-9 mo, 18-24 mo, and 3.25-3.50 yr and then their subsequent referrals for the possible children displaying the symptoms for the disease. five hundred seventy-six underwent this stage.
The referred children undergo secondary screening, “Stage 2”, under the trained eye of a child development physician or a child development teamand when they have failed the test, they will undergo subsequent 2 wk assessment conducted by a multidisciplinary team —speech and language therapist, pediatric physical therapist, occupational therapist, dental nurse, nutritionist, and a nurse specialist in PDDs and associated intervention— using 2-hr activity and play to make PDD diagnosis.
For stage 3, one hundred three children were diagnosed with PDD and 95 % of them underwent Stage 4. Parents naturally accompany their children during the activities. Strong suspects for the disease were further assessed (stage 4), with Autism Diagnostic Interview-Revised algorithm by developmental physicians and those positive for the disease undergo further psychometric assessment— Wechsler Preschool and Primary Scale of Intelligence and the Merrill-Palmer—conducted by a senior educational psychologist. Final diagnosis were carried out using DSM-IV diagnostic criteria to classify the PDD type of disorder.
To test reliability of the study, blinding of 3 trained raters for the 38 AD-R tapes were carried out and then assessed for intraclass correlation coefficiency ( ρsocial interaction=0.82; ρverbal c. = 0.85, ρnon-verbal=0.87; ρrepetitive behavior =0.59, Σ=0.86) and personal assements. Results matched perfectly for the original diagnosis. PDD patients were undergo full laboratory chemistry tests as well as gene map, X test, electroencephalogram, and possibly CT and/or MRI scans (for neurologic damage suspects). Comparison analyses were assessed at Ρ0.05 using Kruskal-Wallis and one-way ANOVA followed by post hoc Scheffé pairwise comparisons.
Analysis for the 97 PDD referrals health visitors as having the highest number of referrals (81%) with the children averaging 35.7 mo at the referral time and 41 mo at the time of clinical diagnosis. Pairwise comparison indicates the order of mean age at the time of the referral for the different groups: Asperger Syndrome (47.5 mo )> PDD-NOS (37.2 mo)> AD (30 mo). ANOVA indicates significances at 11.3 mo and Post-Hoc Schaeffer test indicates similarity of order of mean age to that of non-parametric pairwise comparison.
There were no found differences for syndrome proportionality in the 77 males of the sample population. Thirty percent of the sample population was found to exhibit language impairment characterized by repetitive three-word phrases which was directly correlated to AD subtype. Psychrometric test reveals almost 26 % mental retardation. Two childen with CDD and Rett scored under moderate mental retardation. Chi-square test, P<.001, reveals high likelihood of Autism Disorder displaying mental retardation compared to others.
Sample population also includes five children with PDD sibling; three set PDD-NOS positive, one PDD and PDD-NOS positive and 1 AD and Asperger positive. Siblingrisk calculated from the total pool indicates four percent sibling risk. Chakrabarti and Fombonne castigates similar studies and the reported risk per population at 20/10,000 which is opposed to most literatures that estimated it at 57.9/10000, 67.4 /10 000, and 62.6/10 000. Lower estimations, according to the authors, may be attributed to methodological differences and test insensitivity. Chakrabarti and Fombonne castigates also adds that PDD prevalence can be estimated at 60/10000 and that the cause for PDD increase cannot be totally assessed.
The study’s results indicate the increase in the occurrence of PDD which was attributed to the early detection of disease in children. PDD’s symptoms and levels were not as bad as the older literatures claim and there was an overall decrease in abnormal autism. Unfortunately, AD positive children from the area describe exhibits worse-case AD. Most PDDs identified in 70 % of the population can be classified as Asperger Syndrome or PDD-NOS. Gene roles for were not well established in the study due to lack of causality in the methodology of the study but still the 10 % genetically-identified PDDs in the sample population and sibling recurrence were consistent with other literatures.
PDD population shift have important implications for development of intervention techniques for age cohorts. Early detection before two years of age using highly sensitive and specific screening programs and early intervention can have positive results for recognition and pharmacological management of the disorder.
Limitations for the study include lack of clinical assessment, maldetection of Asperger syndrome whose occurrence can be also detected at the latter age of eight and, misdiagnosis of PDD-NOS for other developmental problems.
Chakrabarti, S. and E. Fombonne. (2001).Pervasive Developmental Disorders in Preschool Children. JAMA. 285: 3093-3099.