Researchers sometimes use insurance claims as a proxy for an autism diagnosis when selecting participants for a study. But few studies have compared the claims with medical records to confirm the diagnoses.

A new study, published 5 June in Autism, compared autism claims from a private U.S. health insurance company with the individuals’ medical histories.

There is nearly a 90 percent chance that people who have filed two or more insurance claims for autism-related services have a diagnosis of autism in their medical records, the study found. This suggests that multiple insurance claims are a good indicator of autism.

The insurer’s database study looked at claims from 23,000 people between the ages of 2 and 20 who had at least one instance of medical, pharmacy or behavioral coverage related to autism.

The researchers looked at a sample of 432 of those people, who had available medical histories and do not have childhood disintegrative disorder or Rett syndrome, which are clinically distinct from autism. They divided the group into three subsets, including 182 people who had two or more autism claims and 190 people who had one.

The third subset included 60 people who had not filed any autism claims. Their medical records all show an autism-related disorder, such as intellectual disability or fragile X syndrome. In addition, one person in the subset does in fact have autism.

The researchers graded each medical chart, looking for autism diagnoses and specific behavioral descriptions that match symptoms described in the Diagnostic and Statistical Manual of Mental Disorders IV.

The researchers found that people with two or more autism claims have an autism diagnosis in their medical histories 87 percent of the time, compared with 74 percent for one claim.

The values dropped when researchers focused on a smaller group of individuals whose medical charts included more thorough descriptions of their behavioral symptoms. This group had more false positives, or people who have autism claims but who do not have autism, according to the criteria.

In this group, there is a 61 percent chance a person has an autism diagnosis if they have two autism claims, and a 43 percent chance if they have one autism claim.