This study found that children with autistic disorder, although not children with Asperger’s disorder or PDD-NOS, received a diagnosis at a younger age than was found in previous studies and that diagnosis occurred at an earlier age among younger children compared with older children. It is important to note, however, that previous studies did not differentiate among ASD subtypes1,18
and reflect diagnostic practices from earlier time periods.33
This issue is especially important because this study suggests that the decrease in age of diagnosis over time is happening more quickly for higher functioning children with ASD. The results also suggest that income, place of residence, clinical presentation, the number of pediatricians that children had before diagnosis, and physician behavior are associated with the age at which children with ASD receive the diagnosis.
Contrary to the previous study in this area,1
ethnic minority children did not receive a diagnosis at an older age than white children. This result may be considered an encouraging finding regarding the elimination of health disparities; it may also be, however, that ethnicity is collinear with other variables, such as income, which had a stronger association with age of diagnosis. Bivariate analyses and tests of statistical interactions did not provide evidence for this hypothesis, however. It also may be that care-givers with greater resources, especially among ethnic minority families, were more likely to respond to the survey, thus biasing the relationship between ethnicity and age of diagnosis.
The relationship between income and age of diagnosis was not linear. Although there was no statistically significant difference between poor families and families whose incomes were >100% above the poverty level, near-poor children received a diagnosis an average of almost 11 months later than children from wealthier families. Income may be related to insurance status, with near-poor families least likely to be insured or to have insurance that fully covers needed services.34–37
Even among the insured, however, access to care may be worse for near-poor families than for those who have public insurance.38
That children in rural settings received a diagnosis later than did children in urban areas echoes findings from a previous study regarding the relationship between urbanicity and the frequency of ASD diagnosis25
and the growing recognition of the importance of place in predicting health and health care in general.39–42
A number of studies have found that children in rural areas have less access to regular and specialty care.43,44
It may also be that a critical mass of children with ASD, which is more likely found in densely populated areas, may increase physicians’ and families’ familiarity with the disorder.
Some symptoms seemed to trigger earlier diagnosis than others. Children with severe language deficits, hand flapping, toe walking, and sustained odd play received a diagnosis earlier. Although language deficits are an important component of diagnosis for autistic disorder and PDD-NOS, the other 3 symptoms are not required for diagnosis. Physicians may be more familiar with these symptoms from portrayals of ASD in the popular media, or they may be more disturbing to parents and physicians alike, prompting additional evaluation. The association of oversensitivity to pain with later diagnosis may be because this symptom prompts clinicians to search for other organic causes and not consider developmental issues. Similarly, ASD symptoms in adopted children, who received a diagnosis almost 10 months later than other children, may be attributed to factors associated with early childhood experiences that result in temporary delay rather than a condition associated with chronic delay such as ASD.
Children with hearing impairments received a diagnosis almost 10 months later than other children. Hearing loss may make it more difficult to determine the presence of ASD; however, the frequent co-occurrence of ASD and hearing impairment (as well as mental retardation and seizures)45
should alert clinicians to the possibility of ASD in this group.
Families’ interactions with the health system were also associated with differences in the age of diagnosis. Children who had 4 or more primary care physicians before diagnosis received a diagnosis 6 months later than other children, whereas children whose pediatricians referred them to specialists in response to developmental concerns received a diagnosis earlier than did other children. Having many primary care physicians before diagnosis may be related to issues such as residential instability and poor access to health care that result in discontinuity of care, or parents could not recognize the importance of continuous pediatric care. Alternatively, switching physicians may be the result of families’ frustration that their concerns are not being acknowledged or addressed.
It was disappointing to note that conducting developmental tests was not associated with a decrease in the age of diagnosis, especially in light of current federally funded efforts and American Academy of Pediatrics guidelines focused on increasing standardized, regular developmental screening. It may be that caregivers’ report of whether physicians conducted testing is an invalid measure, whereas physician referrals are easier to ascertain accurately. In addition, the measures that physicians used may not be sensitive to the presence of ASD. A number of studies suggest that more physicians rely on clinical judgment or a few questions more than on standardized measures.46–50
Unless validated measures are implemented in a reliable manner, it may be more effective for physicians to rely on parental concern as a measure of need.51,52
A number of study limitations should be considered. Perhaps primary among them is the validity of ASD diagnoses and reporting of related symptoms, which were not standardized or validated. All respondents indicated that the diagnosis was made by a physician or a psychologist, however, and studies have found good to excellent reliability associated with both the diagnosis of ASD by health care professionals and the differentiation of subtypes.53–56
A related limitation is that we collected data only on some symptoms associated with ASD. Given the length of the survey, our goal was to focus only on those symptoms that we thought might differentiate subtypes of children with ASD. In the process, we may have missed important symptoms that are associated with changes in the age of diagnosis. For example, we do not have information on IQ other than the presence of mental retardation and have limited information on issues related to social interactions. A third limitation is the potential bias in survey respondents, especially given the sampling method. Despite the similarities between the experiences and ethnicity of survey respondents and children with ASD in Pennsylvania described in Methods, families who were motivated to complete this survey may have characteristics and experiences different from those of nonresponders. An indication of bias toward higher functioning children in this sample is the large number of responding families relative to the known community prevalence of children with Asperger’s disorder and without mental retardation.57
A fourth limitation is that caregivers were asked to recall events that may have happened much earlier. Differential recall about, for example, pediatrician behavior or age of diagnosis may have biased the results.
Despite these limitations, there are a number of study implications. The results provide some evidence regarding the positive effects of having continuity in pediatric care. The American Academy of Pediatrics emphasizes the importance of coordinated, continuous health care for children with ASD,2
and research shows the importance of this type of care in improving outcomes for children with special health care needs58,59
; however, fewer than half of children with special health care needs have care that meets these criteria.60,61
The reason for the discontinuity among children with ASD, whether it relates to access or frustration, for example, has important implications for the interventions to reduce it.
This study also suggests the importance of specialist referrals. The symptoms of ASD are sometimes difficult to differentiate from other health conditions,62
and generalists may not associate some of them with ASD. Specialist referrals for ASD are often accompanied by long wait times,18
however, and especially in rural settings and for uninsured or underinsured families, referrals may not be readily available. For example, the American Board of Pediatrics workforce report shows the paucity of board-certified developmental pediatricians and pediatric neurologists in many states.63
Other studies have found that children with ASD have more difficulty obtaining specialty care than children with other special health care needs.64
These data suggest the importance of parallel efforts to increase both the availability of specialist care for diagnosis and physician knowledge of the multiple ways in which ASD can manifest.65