Characteristics of False Positives On the ADI-R in An Adult Sample

Background: Limited research has been conducted on diagnosing adults with autism spectrum disorders (ASD). Previous studies have shown that diagnosing adults is difficult due to scarce and inconsistent information relating to the manifestation of ASD in adulthood.  Symptoms of ASD in an individual may change over the life course due to maturation, environmental influences, and treatments and services. Life experiences may also cause individuals to appear to have ASD in adulthood. Current diagnostic instruments have not been validated in adult use and do not take into account the effect life occurrences may have on the presentation of ASD in adults. This may lead to a potential mistake in diagnosis of ASD in adults. 

Objectives: To identify characteristics, among adults who meet ADI-R criteria for an ASD, that discriminate between true and false positives.

Methods: The sample included 322 civilly-committed patients in one state psychiatric hospital in Pennsylvania.  Nursing staff completed the Social Responsiveness Scale (SRS) for each patient as part of standard of care. All patients with scores ≥ 100 on the SRS and a stratified random sample of those with lower scores were consented to conduct in-depth chart reviews and contact family members to conduct the Autism Diagnostic Interview-Revised (ADI-R) and Conflict Tactics Scales: Parent-Child Version (CTS-PC). Chart reviews focused on developmental history, paying particular attention to age of onset and clinical features indicative of ASD. Data on medications, self-injurious behaviors, and physical/mechanical restraints were collected for each consented patient.  Case conferences with two psychiatrists and the team of assessing psychologists were held for all patients. After case conferences were completed, the patients who were identified as having ASD on the ADI-R were further examined to identify differences between false positives and true positives.

Results: Case conferences as well as ADI-R and CTS-PC administration are ongoing. Twenty-two percent of patients with completed ADI-R interviews definitely or are highly to likely meet criteria for an ASD. Only 50% of subjects scoring positively on the ADI-R definitely met criteria for ASD based on record review and expert clinical judgment.  Chart review found that all false positives experienced some form of abuse (physical, psychological, or sexual).  In addition, all of the possible cases of ASD had a history of abuse. Only 29% of cases meeting research criteria for ASD had a history of abuse.  Formal analysis of other characteristics that discriminate false positives from true positives is ongoing.  To date, no differences between the false positives and true positives in patterns of responses on the ADI-R have been identified. Preliminary results indicate that false positives who have experienced abuse also have a more recent history of criminal involvement and substance abuse, while those meeting research criteria for ASD do not.

Conclusions: Even in an institutionalized adult population, the ADI-R is a useful tool. Our results suggest, however, the need for different cut-offs and to augment the ADI-R with other information, especially about physical, sexual and substance abuse history.