Getting an autism diagnosis could be more difficult in 2013 when a revised diagnostic definition goes into effect. The proposed changes may affect the proportion of individuals who qualify for a diagnosis of autism spectrum disorder, according to preliminary data presented by Yale School of Medicine researchers at a meeting of the Icelandic Medical Association.

The proposed changes to the diagnostic definition would be published in the fifth edition of the American Psychiatric Association's (APA) "Diagnostic and Statistical Manual of Mental Disorders (DSM-5)."

"Given the potential implications of these findings for service eligibility, our findings offer important information for consideration by the task force finalizing DSM-5 diagnostic criteria," said Yale Child Study Center (CSC) director Fred Volkmar, M.D., who conducted the study with CSC colleagues Brian Reichow and James McPartland.

Volkmar and his team found that in a group of individuals without intellectual disabilities who were evaluated during the 1994 DSM-IV field trial, it was estimated that approximately half might not qualify for a diagnosis of autism under the proposed new definition.

Volkmar stressed that these preliminary findings relate only to the most cognitively able and may have less impact on diagnosis of more cognitively disabled people. "Use of such labels, particularly in the United States, can have important implications for service," he said. "Major changes in diagnosis also pose issues for comparing results across research studies."

Volkmar first presented the preliminary research results in September at Yale and in October at the Institute On Autism American Academy of Child Adolescent Psychiatry Meeting In Toronto. Volkmar and colleagues will publish full study results in the April print edition of the Journal of the American Academy of Child and Adolescent Psychiatry. The study may be available online as early as late February or early March.