Genetic Testing History in Adults with Autism Spectrum Disorder

This study of 630 adults with autism spectrum disorder reveals that genetic testing is significantly underutilized, with only 41% having documented testing history and just 28% of those tested receiving a positive genetic diagnosis, highlighting a critical need for increased screening and adherence to recommended testing protocols in adult ASD care.

The Gist

Imagine Autism Spectrum Disorder (ASD) as a massive, complex library. For decades, we knew the books (the people) were there, and we knew the stories were different, but we didn't always know who wrote them or why the stories unfolded the way they did.

In recent years, scientists have developed a powerful new "indexing system" called genetic testing. This system can scan a person's DNA to find the specific "author" or "blueprint" behind their autism. Knowing the blueprint helps doctors predict health risks, connect families with support groups, and even find new medicines.

However, a new study from a major autism clinic in Massachusetts asks a simple but startling question: How many adults with autism have actually had their books indexed?

Here is the breakdown of the study, translated into everyday language:

1. The Big Reveal: The Library is Missing Half Its Index Cards

The researchers looked at 630 adults with confirmed autism who visited their specialized clinic between 2010 and 2020. They wanted to see if these adults had ever been given the "genetic test."

• The Result: Only 41% of these adults had a record of having been tested.
• The Gap: For nearly half the group (47%), there was no record at all. It's like walking into a library and realizing that for almost half the books, the catalog card is missing. We don't know if they were never tested, or if the test was done but the paperwork got lost in the shuffle.
• The Refusal: About 11% of families explicitly said "no, we don't want the test."

2. The Tools: Using an Old Map vs. a GPS

Even among the people who did get tested, the study found they were often using outdated tools.

• The Old Map: Many adults received older tests (like checking for Fragile X or looking at chromosomes under a microscope). These are like using a paper map from the 1990s. They work, but they miss a lot of detail.
• The GPS: Modern medicine now recommends "Exome Sequencing" or "Gene Panels." These are like high-tech GPS systems that can pinpoint the exact location of a problem in the DNA.
• The Problem: Only 54% of the people who were tested actually got the modern "GPS" test. The rest were stuck with the old paper maps.

3. The Treasure Hunt: Finding the "Why"

When the researchers looked at the results of the modern tests (the ones we recommend today), they found something exciting.

• The Hit Rate: In 28% of the cases where the modern test was used, they found a specific genetic cause.
• Why this matters: Imagine you've been driving a car that keeps stalling for 30 years. You've been told, "Just drive carefully." Then, a mechanic finally opens the hood and says, "Ah, there's a broken wire in the fuel line."
  • Medical Safety: If that broken wire is linked to a higher risk of cancer or heart issues, the patient can get screened early. This can literally be lifesaving.
  • Ending the Guilt: For many parents, finding a genetic cause is like finding a missing puzzle piece. It stops them from wondering, "Did I do something wrong during pregnancy?" The answer is often, "No, it's just how the blueprint was written."
  • Community: It helps families find others with the exact same genetic blueprint, creating a support network that feels like finding your tribe.

4. Why Didn't Everyone Get Tested?

The study suggests a few reasons why the "indexing" hasn't happened for everyone:

• The "Too Old" Myth: Many doctors (and families) think genetic testing is only for children. They assume, "Well, they are 30 now, the test won't help." The study proves this is wrong; the test is just as valuable for adults.
• The "No Symptoms" Myth: Some people thought, "My adult child is smart and doesn't have seizures, so they don't need a test." But the study showed that even adults without other major health issues often have a genetic cause that was missed.
• The "Declined" Factor: In the past, some families were offered the test and said no, perhaps because they didn't understand the benefits or were worried about insurance.

The Bottom Line

This study is a wake-up call. It's like realizing that a huge portion of the population is walking around with a "User Manual" for their body that they've never been allowed to read.

The Takeaway:
Just because someone is an adult doesn't mean they've "outgrown" the need for genetic answers. The authors are urging doctors to look at their adult patients and ask: "Have we checked the genetic blueprint yet? If not, let's do it."

By updating the "index" for these adults, we can unlock better healthcare, end decades of parental guilt, and help people understand their own unique stories a little better.

Technical Summary

1. Problem Statement

Despite the identification of numerous genes associated with Autism Spectrum Disorder (ASD) and evolving clinical guidelines recommending genetic testing (e.g., chromosomal microarray, exome sequencing), there is a significant knowledge gap regarding the uptake and outcomes of these tests in adults with ASD.

• The Gap: While testing is standard for children, it is unclear how many adults with ASD have received recommended genetic testing, what methods were used, and the diagnostic yield in this population.
• Clinical Context: Identifying a genetic etiology is crucial for prognosis, managing co-occurring medical conditions (e.g., cancer risks in PTEN variants), reducing parental guilt, and facilitating personalized medicine. However, historical data suggests low testing rates in adult cohorts, and the transition from older testing methods (karyotype, Fragile X) to newer high-yield methods (gene panels, whole exome sequencing) has not been fully evaluated in adult clinical settings.

2. Methodology

Study Design:

• Type: Retrospective chart review study.
• Setting: Massachusetts General Hospital (MGH) Lurie Center for Autism, a specialized adult ASD clinic.
• Timeframe: Patients with at least one visit between May 1, 2010, and December 15, 2020.

Participants:

• Total Cohort: $N = 630$ adults with confirmed ASD diagnoses.
• Inclusion Criteria: Past or current patients at MGH Lurie Center; documented developmental history; comprehensive clinical evaluation by a specialist (psychiatrist, neurologist, etc.); confirmed ASD diagnosis via record review by expert psychiatrists.
• Demographics: Mean age 29.6 years (SD 7.1); 23% female; 73% with intellectual disability (ID); 89% White.

Data Collection & Analysis:

• Data Sources: Electronic Health Records (EHR) and the Research Patient Data Registry (RPDR).
• Variables: Demographics, clinical history (seizures, ID, dysmorphic features), and genetic testing history (type, date, results).
• Classification of Testing:
  • Recommended Methods: Chromosomal microarray (CMA), Autism/ID sequencing panels, or Exome Sequencing (ES).
  • Non-Recommended/Other: Karyotype only, Fragile X only, or other non-standard methods.
• Statistical Approach:
  • Descriptive statistics for demographics and testing history.
  • Robust linear regression and Chi-square tests to compare groups (tested vs. untested vs. declined).
  • Relative risk regression models (modified Poisson approach) to identify predictors of receiving recommended testing.
  • Wilson's and Goodman's methods for calculating 95% confidence intervals (CIs).

3. Key Contributions

• First Large-Scale Adult Cohort Analysis: Provides one of the largest retrospective analyses ($N=630$) specifically focused on genetic testing utilization in adults with ASD, a population often excluded from pediatric-centric genetic studies.
• Documentation of the "Testing Gap": Quantifies the disparity between current guidelines and actual clinical practice in adults, highlighting that nearly half of the cohort lacked documentation of any genetic testing.
• Diagnostic Yield in Adults: Establishes the diagnostic yield of recommended testing methods specifically within an adult population, demonstrating that a significant portion of adults remain undiagnosed genetically despite the availability of advanced testing.
• Predictors of Testing: Identifies specific clinical phenotypes (e.g., microcephaly, macrocephaly, dysmorphic features, seizure history) that are associated with a higher likelihood of receiving recommended genetic testing.

4. Key Results

Testing Utilization:

• Documentation Rate: Only 41% (261/630) of adults had documented genetic testing in their records.
• Declined/Unrecorded: 11% declined testing; 47% had no record of testing (suggesting the true rate may be even lower).
• Methodology: Among those with documented testing ($N=238$), only 54% received a "recommended" method (CMA, panel, or ES).
  • Older methods (Fragile X, Karyotype, CMA) were dominant.
  • Newer methods (Gene Panels: 7%; Exome Sequencing: 7%) were rarely used.

Diagnostic Yield:

• Positive Findings: Among adults who underwent at least one recommended method, 28% (95% CI: 19%, 39%) received a positive genetic diagnosis.
• Breakdown by Method:
  • Chromosomal Microarray: 23% positive yield.
  • Gene Panel: 1 positive result (out of 15), but 47% had Variants of Unknown Significance (VUS).
  • Exome Sequencing: 47% positive yield (7/15), with an additional 13% VUS.
• Low-Risk Phenotypes: Even in adults without ID, seizures, or dysmorphic features ($N=16$), 25% had positive results from recommended testing.

Predictors:

• Presence of microcephaly, macrocephaly, or dysmorphic facial features was associated with a 1.58x higher frequency of receiving recommended testing.
• Seizure history was associated with a 1.29x higher frequency of recommended testing.
• Age, sex, and ID status were not significantly associated with receiving recommended testing in multivariate models.

5. Significance and Implications

• Clinical Practice: The study strongly advocates for the routine review of genetic testing history in adult ASD clinics. Many adults have not received testing, and those who did often received outdated, lower-yield methods.
• Personalized Medicine: Identifying genetic causes (e.g., MECP2 variants) allows for targeted therapies (e.g., trofinetide for Rett syndrome) and proactive management of associated medical risks (e.g., cancer screening).
• Psychosocial Impact: Genetic diagnosis can alleviate parental guilt regarding the etiology of ASD and connect families to specific support groups and research studies (e.g., SPARK).
• Future Directions: As insurance coverage for Whole Exome Sequencing (WES) improves and gene panels expand, the diagnostic yield for adults is expected to rise. The authors suggest that the current low testing rates represent a missed opportunity for clinical care and research stratification to reduce phenotypic heterogeneity in ASD studies.

Limitations Noted:

• Demographics: The cohort was predominantly White (89%) and male (74%), which may not reflect the broader community prevalence.
• Documentation Bias: The study relies on EHR documentation; lack of record does not definitively prove lack of testing, though it suggests a systemic documentation gap.
• Time Period: Data ends in 2020; testing practices and insurance coverage have evolved significantly since (e.g., wider adoption of WES).