Trends in autism prevalence: diagnostic substitution revisited.

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http://www.ncbi.nlm.nih.gov/pubmed/17975721

Trends in autism prevalence: diagnostic substitution revisited.Coo H,

Ouellette-Kuntz H, Lloyd JE, Kasmara L, Holden JJ, ME.

Department of Community Health and Epidemiology, Queen's University, c/o

Ongwanada Resource Centre, 191 Portsmouth Avenue, Kingston, ON, Canada, K7M 8A6.

There has been little evidence to support the hypothesis that diagnostic

substitution may contribute to increases in the administrative prevalence of

autism. We examined trends in assignment of special education codes to British

Columbia (BC) school children who had an autism code in at least 1 year between

1996 and 2004, inclusive. The proportion of children with an autism code

increased from 12.3/10,000 in 1996 to 43.1/10,000 in 2004; 51.9% of this

increase was attributable to children switching from another special education

classification to autism (16.0/10,000). Taking into account the reverse

situation (children with an autism code switching to another special education

category (5.9/10.000)), diagnostic substitution accounted for at least one-third

of the increase in autism prevalence over the study period.

PMID: 17975721 [PubMed - in process]

NOTE: This does imply that 2/3 of the increase cannot be explained away by

better awareness. It is also interesting to note that this study found

diagnostic substitution works in both directions, something the Fombonnes never

seem to mention.