The first major rewrite of the diagnostic guide used by the nation's psychiatrists is approved.

CHICAGO — The now familiar term “Asperger disorder” is being dropped. “Dyslexia” and other learning disorders remain.

The revisions come in the first major rewrite in nearly 20 years of the diagnostic guide used by the nation’s psychiatrists. Changes were approved Saturday.

Full details of all the revisions will come in May when the American Psychiatric Association’s new diagnostic manual is published, but the impact will be huge, affecting millions of children and adults worldwide. The manual also is important for the insurance industry in deciding what treatment to pay for, and it helps schools decide how to allot special-education resources.

The changes were approved Saturday in suburban Washington, D.C., by the psychiatric association’s board of trustees.

The aim of the revision is to ensure that affected children and adults are more accurately diagnosed so they can get the most appropriate treatment, said Dr. David Kupfer. He chaired the task force in charge of revising the manual.

One of the most hotly argued changes was how to define the ranges of autism. Some advocates opposed the idea of dropping the specific diagnosis for Asperger disorder. Some Asperger families opposed any change, fearing their children would lose a diagnosis and no longer be eligible for special services.

But the revision will not affect their education services, experts say. The new manual adds the term “autism spectrum disorder,” which already is used by many experts. Asperger disorder will be dropped and incorporated under that umbrella diagnosis.

The new manual also will have a broader learning-disorder category to cover several conditions including dyslexia, which causes difficulty understanding letters and recognizing written words.

Group leaders said specifics won’t be disclosed until the manual is published, but they confirmed some changes, including:

• A new diagnosis for severe recurrent temper tantrums: disruptive mood dysregulation disorder, or DMDD.

• Eliminating “gender identity disorder” and replacing it with “gender dysphoria,” which means emotional distress over one’s gender.