One in 44 children in the United States are now diagnosed with autism, and the rate is still rising. What has been unclear is whether the incidence of autism is actually increasing or if clinicians and parents are getting better at identifying and screening for symptoms. Autism spectrum disorder (ASD) is also still diagnosed in a subjective way - based on a child's behavior, and there is no diagnostic test for molecular markers of ASD. If screening can be fully standardized, it may inform our understanding of the disease and lead to better treatments. It can also help patients get diagnosed earlier so that interventions can be applied sooner, potentially limiting the impacts of the disorder.
Two new studies have examined the efficacy of a commonly used autism spectrum disorder screening tool called Modified Checklist for Autism in Toddlers (M-CHAT) and its updated version M-CHAT, Revised with Follow-Up (M-CHAT-R/F).
Reporting in JAMA Pediatrics, researchers have reviewed about 50 studies that have analyzed these diagnostic tools. The study authors have suggested that in clinical settings, the tests are often applied in ways that differ from the original validation studies, which can impede our ability to measure their effectiveness. The performance review of the tests, called M-CHAT and M-CHAT-R/F indicated, however, that the tests are still good at detecting autism.
"M-CHAT(-R/F) shows strong performance as an autism screener," said first study author Andrea Wieckowski, Ph.D., an assistant professor at the Autism Institute. "We found that across the studies, there was 83 percent sensitivity, or ability to detect autism when present. Specificity, or ability to accurately rule out autism, was 94 percent, indicating its strong performance."
The variability of the results also highlighted, however, that clinicians should adhere to the test standards. Problems include pediatric practices where there is a disregard for administering follow-up tests. Children are often not screened repeatedly, and those who are identified as positive cases are not always referred for treatment
Another meta-analysis of the same tests was reported in the journal Pediatrics, and it came to a different conclusion. This work suggested that the test was not performing that well as a lone, or single-use diagnostic tool. The study indicated that children who are tested with M-CHAT or M-CHAR-R/F and given a postive screen, meaning they probably have autism, are only confirmed to have autism after an additional assessment 57.7 percent of the time. In addition, nearly 28 percent of children who get a negative screen, meaning they probably do not have autism, are later diagnosed with autism.
The study authors noted that the test is still a worthwhile tool, but it has to be used properly and with caution and follow-up. It is only a screening method, so positive results are not a diagnosis, and negative screens don't absolutely rule out autism.
"I think the most important takeaway from this study is that the M-CHAT-R/F is a screening tool with limitations," said study co-author Van Ma, a developmental-behavioral pediatrics fellow at the MIND Institute. It has a role in screening for autism but is not meant to replace clinical judgment and comprehensive diagnostic assessment."
"It is so important for clinicians to think carefully about the results of the screening test, to neither unnecessarily concern parents nor to inaccurately reassure parents," added senior study author Heidi Feldman, professor and chief of the Division of Developmental-Behavioral Pediatrics at Stanford University.
A new report in the Journal of Autism and Developmental Disorders has also noted that girls are more difficult to diagnose for autism than boys because their neurodivergent behavior can be more difficult to detect. Girls with autism tend to have more subtle challenges, and often appear to be developing normally, the study indicated.
Sources: Drexel University, UC Davis MIND Institute, American Academy of Pediatrics, JAMA Pediatrics, Pediatrics, Journal of Autism and Developmental Disorders
