Overview of PDD categories in ICD-10 and DSM-IV-TR.
Disabled persons live in every corner of the world and on all social levels. According to UN estimations, disabilities are much more widespread than is believed: at least one in every 10 inhabitants of each country has a certain form of disability, totaling some 450 million people around the world.  According to the 2001 census, Croatia had at that time 423 891 persons with disabilities (10% of overall population) . According to the Croatian Disabilities Registry (the Registry), , Croatia has 518 081 disabled persons (ca. 12% of overall population). As defined in the Act on the Croatian Disabilities Registry, disability is a limitation or reduction (resulting from damaged health) the capacity to perform a certain physical activity or psychological function normal for a person of a certain age, and refers to the abilities which are manifested in complex activities and behaviors generally accepted as important components of everyday life . Croatia has defined the collection of data on disabled persons in the Act on the Croatian Disabilities Registry (Official Gazette No. 64/01). The Registry includes data on the following types of physical and mental impairments: visual, hearing and speech impairments, impairments of the locomotor, central and peripheral nervous systems, other organs and organ systems, mental retardation, PDDs (autism), mental disorders, as well as data on multiple impairments. PDDs (autism) have been separated as a special disability category. The data on the above disorders is provided by expert evaluation bodies within the education and social welfare system . According to the references, PDD prevalence has registered a continual rise. To illustrate, according to the CDC Report from Atlanta, USA, prevalence numbers 6.6 per 1000. [5, 6, 7, 8, 9]. The data on individuals with PDDs in Croatia is registered in the above Registry. However, due to a short history (since 2002), the extent of the potential increase could not be determined.
2. Epidemiology of PDDs globally
2.1. Classification systems
For the purpose of learning more about the epidemiology of autism, and, by extension, about the changes in its prevalence, the following part will present two classification systems that have been in international use for many years, together with clearly stated criteria and diagnostic instructions that need to be abided by so as to correctly diagnose autism and PDDs. The two systems are: WHO’s ICD-10 (
|F 84.0||Childhood autism||299.00||Autistic disorder|
|F 84.2||Rett's syndrome||299.80||Rett’s disorder|
|F84.3||Other childhood disintegrative disorders||299.10||Childhood disintegrative disorder|
|F 84.4||Overactive disorder associated with mental retardation and stereotyped movements|
|F84.5||Asperger's syndrome||299.80||Asperger’s disorder|
|F84.8||Other pervasive developmental disorders||PDDNOS|
|F84.9||Pervasive developmental disorder, unspecified||299.80||PDDNOS|
2.2. Epidemiological studies on autism
The first epidemiological study of autistic disorder was published in 1966. Viktor Loter, the author, thereby informed the health public that the prevalence of autistic disorder was low, namely four to five autistic children per 10 000 inhabitants . Epidemiological studies in 1980s and 1990s registered a significant increase in the prevalence of autistic disorder in different parts of the world. Research done in Wales has shown that autism prevalence in respondents born between 1977 and 1979 was 3.3, while the prevalence in the population born between 1987 and 1989 9.2 . The prevalence of autism in Iceland grew from 4.2 persons in respondents born between 1974 and 1983 to 13.2 in the population born between 1984 and 1993 . A stable growth in the prevalence of autism during the 1980s and 1990s was also registered in California . Having analyzed a sample of some 300 000 respondents born between 1988 and 1996, Honda noted that the incidence of autism grew from an earlier 54 to the present 88 persons, with the highest oscillation being registered in the 1990s . Fombonne conducted a meta-analysis of 32 epidemiological studies on autistic disorder carried out between 1966 and 2001. Data was collected on the prevalence of autistic disorder in 13 different countries on a sample of nearly 5 million people. According to the epidemiological research of the same author, 13 in 10 000 liveborn children are born with autism, 3 with Asperger’s syndrome, and 60 with PDDs . Similar data are found in studies of other authors (21,22). According to the CDC Report, the prevalence rate for autism numbers 6.6 per 1000 [5, 6, 7, 8]. Autism more commonly appears in boys, accounting for the ratio of 4.3:1 in favor of boys . According the cohort study of children in South Thames prevalance of ASD was about 1%  while in the past year a new epidemological study rates closer to 2% . Regarding the prevalence of PDDs in EU countries, EUGLOREH 2007 stressed the diversity of the definition of autistic disorder and methodology yielding and monitoring prevalence, which is confirmed by Table 2. Specially stressed is the need to approximate the above segments .
|Aarhus (Denmark)||1972||46 500||Kanner||2-14||4.3|
|Camberwell (UK)||1979||34 700||Kanner||3-17||4.9|
|Cambridgeshire (UK)||1999||34 262||DSM-IV||5-11||57|
|Västerbotten (Sweden)||1983||69 600||Rutter||0-20||5.6|
|Göteborg1 (Sweden)||1984||128 600||DSM III||4-18||4|
|Göteborg2 (Sweden)||1986||42 900||DSM III||0-10||7.5|
|Göteborg3 (Sweden)||1991||40 700||DSM III - R||4-13||11.5|
|Rhône (France)||1989||103 700||Rutter||5-9||10.8|
|Northern Finland||1997||152 732||DSM III – R/DSM-IV||5-7||20.7|
|Ireland East||1997||549 255||DSM III /DSM III - R||0-25||4.94|
The above data leads to the conclusion that the prevalence of autistic disorder in the last 50 years has increased as much as 15 times. Does that mean that the modern world is facing a kind of an
3. Prevalence of PDDs in Croatia
Croatia monitors data on persons with PDDs within the scope of the Registry. PDDs are therein separated as a special type of disability and monitored according to the ICD-10 under the three-sign category of F84. The onset of a systematic epidemiological monitoring of data on PDDs goes back to the introduction of the Registry in 2002. The data on the above disorders is provided by expert evaluation bodies within the education and social welfare system. These expert evaluation bodies hire experts who are to thank for PDD diagnostics. The Registry database, as up until 4 May 2012, contains data on 1109 persons with PDDs, with the largest number of registered under the diagnosis F84.9 (Table 3).
|F 84.0||Childhood autism||267|
|F 84.2||Rett's syndrome||24|
|F84.3||Other childhood disintegrative disorders||18|
|F 84.4||Overactive disorder associated with mental retardation and stereotyped movements||30|
|F84.8||Other pervasive developmental disorders||19|
|F84.9||Pervasive developmental disorder, unspecified||650|
The prevalence of PDDs in the overall population of the Republic of Croatia is about 2-3/10 000, while in children (population aged 0-18) ca. 1/1000, with three times higher incidence in boys. In Register we see increase (2.6x) number of registrated person with ASD in last seven years (304 registrated person until 01.01.2005. and 792 after that date). The largest number of persons with PDDs, namely 759 (70%), belong to the 5–19 age group (Table 4). Primorsko goranska county and City of Zagreb number the highest prevalence in childhood at just above 1/1000.
|As amended on 5 May 2012|
All the above leads to the conclusion that there is a difference between the registered prevalences of PDDs in Croatia and other countries of the world. According to the last available CDC data, global prevalence reaches 6.6 per 1000, while in Croatia the rate is ca. 1 in 1000 children (0-18 age group). This great discrepancy, that is under registration of PDDs, could be explained by numerous factors. One of them could be the phenomenon of