A brief history

The 3di was initially developed as a research tool starting around 1998 at the Great Ormond Street Institute of Child Health under the direction of Professor David Skuse. The World Health Organisation's International Statistical Classification of Diseases and Related Health Problems, 10th revision, or ICD-10, came into effect in 1993. Meanwhile the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, fourth edition, or DSM-IV, was published in 1994. The 3di treated the two systems as broadly equivalent, and the 3di's first ASD assessment was built around an amalgamation of ICD-10 and DSM-IV criteria.

The first autism assessment in the 3di, now known as the ICD-10 extended, contained 134 questions, and was designed for research use where there was sufficient time for such a thorough assessment.

Over the following years, demand grew for a quicker autism informant interview for use in CAMHS clinics where there was less time available. This led to the development of the ICD-10 brief assessment.

DSM-5 came into effect in 2013, followed by ICD-11 in 2022. The 3di was updated with a new DSM-5 extended assessment for autism in 2013. Finally in late 2022 the DSM-5 brief assessment was released.

Comparing DSM-5 and ICD-11, we consider that by design the two sets of criteria are so similar that ASD outcomes (and many others) can be reported as DSM-5 or as ICD-11. The 3di always references DSM-5 because the APA got there many years before the WHO; you can substitute one term for the other in your reports or perhaps reference neither.