On the basis of 10 479 simple screening forms administered at the first-year pediatric examination, 32 infants were identified as having ASD. Current epidemiologic estimates report that 65 of every 10 000 infants born will be diagnosed as having an ASD by early childhood.22
Given that late onset (approximately 20% of cases), regression (25% of cases23
), and Asperger’s cases (10% of cases24
) would not be expected to be detected by screening at the first birthday, rates obtained by this study are in alignment with what would be predicted on the basis of current prevalence rates. The strategy outlined here thus provides a simple mechanism for research laboratories to study autism beginning at 12 months. The ability to study autism in the general population before
the onset of obvious symptoms may be particularly important for research studies aimed at identifying early biomarkers of the disorder. Furthermore, the 1-Year Well-Baby Check-Up Approach not only successfully identified early cases of autism, but also 56 cases of LD and nine cases of DD that stand as important research contrast groups.
The standard of clinical care was dramatically changed for infants in San Diego with relatively little effort on the part of participating pediatric offices. In a strong display of collaboration, 137 pediatricians actively and consistently screened infants at 1 year and are continuing to do so today. Before participation in this study, only 22% of pediatricians were consistently screening at 1 year. In contrast to other population-based screening studies that used screens that were mailed in or received from multiple child and health care agencies,12,25
this study reflects a valid assessment of what can be achieved in real-world pediatric practice. Specifically, screens were filled out and scored as part of the normal 1-year check-up appointment and were not received from any other source.
On the basis of the sample of children who were tracked in this study, our results suggest that approximately 20% of infants who fail the CSBS-DP-IT-Checklist at the 12-month pediatric check-up will manifest an ASD, 55% will manifest an LD, general DD, or associated issue, and 25% will have a false-positive result. No selection criteria, exclusionary criteria, or phone screening occurred when parents called our laboratory for an evaluation; parents were simply following their pediatrician’s recommendation for an evaluation, and participation was granted to all callers equally.
It is also important to consider how this study differs from the many important screening studies that preceded it.12,26–30
In contrast to studies in primary medical settings that focus on 18 months and older,26–28
this is the first and only study that demonstrates the feasibility of using a broad screen in a medical setting to detect autism as young as 12 months. Additionally, unlike other studies wherein a research assistant approached every parent in a waiting room and obtained informed consent,26
this study evaluated the ease with which a pediatricians’ office could actually implement the screening process with their own employees and not research assistants. Although a promising new autism toddler screen, the Early Screening of Autistic Traits Questionnaire, has been developed, the full screen has not been tested for use in a pediatrician’s office but rather was administered in the home setting at a mean age of 16 months,30
and infants did not receive a full developmental evaluation until an average of 24 months. Furthermore, field test results for the Early Screening of Autistic Traits Questionnaire indicated that of >36 000 infants screened, only 18 were identified as having ASD. In this study 32 infants with ASD were identified with far fewer screens (ie, 10 479), suggesting that the CSBS-DP-IT-Checklist may be particularly effective as an early screening tool for autism. The study by Wetherby et al12
focused on the CSBS-DP-IT Checklist. In that study parents in the general community were first mailed an information packet, and interested parents returned the completed screening form anytime when their infant was between 6 and 24 months via mail. There was the potential for a selection bias in that parents with strong concerns about their infant were more likely to return the screening form.12
Results from this study, which screened solely in pediatric offices and were possibly less susceptible to selection bias, found an almost identical positive predictive value at 12 months (75%) compared with what was found by the mail-in study by Wetherby et al12
at 12 months (73%). Combined results from both studies thus provide confidence in the CSBS-DP-IT-Checklist as an early screen to detect a wide range of delays.
Beyond the high research potential of using the CSBS-DP-IT-Checklist at all 1-year check-ups, this program also successfully initiated treatment targeting language, social, and cognitive skills for the vast majority of infants with an ASD, LD, or DD between the ages of 12 to 24 months. It is unlikely that treatment would have been initiated for these children at such an early age had it not been for this program. Almost all treatments were behaviorally based, with the most common modalities being speech therapy, discrete trial training, and pivotal response training. Overall, infants received an average of 7.6 hours of one-on-one treatment per week, with a greater number of treatment hours for the children with DD and ASD in comparison with those with LD. Most of these infants began treatment at or before 18 months in age.
There are, however, some limitations to the inferences one can draw from this study. Although clinically desirable and a possible line of future inquiry, this study did not set out to determine sensitivity and specificity of the CSBS-DP-IT-Checklist. The initial validation study of the instrument,12,13
not conducted in pediatric offices and with slightly older children, estimated good sensitivity (88.9%) and specificity (94%). Data from this study are not well-suited to replicate and extend these findings because only 41 infants who passed the initial screening were followed, and estimates of sensitivity and specificity, which take into account both true- and false-negative results, are strongly influenced by the number of infants tracked who passed the initial screening. Our data do speak to the estimated positive predictive value of the screening, however, because positive predictive value takes into account only infants who failed the screening, and we were able to track 184 such infants. We were also able to note that, similar to findings from the later validation study,12
there is a somewhat high-false positive rate of the CSBS-DP-IT-Checklist. Another potential limitation is that 28% of the toddlers with ASD in the sample have not been monitored through to the full 32 to 36 months of age called for in the study (but rather only until 24 months). It is possible that some diagnoses may change in this small group, although several studies have empirically demonstrated the stability of diagnoses at or around 24 months.18–20,31
Although the utility of this approach for detecting young ASD cases around the first birthday is strong, future iterations of this program could be improved if a second screening were administered 1 year later, at 24 months, to detect late onset and regression cases that were missed by the 12-month screening. Future versions of this program should also attempt to improve the tracking of infants who failed the screening form but were not actually referred for participation in the program. The large discrepancy between the number of failures and the number of referrals to the program could be due to a lack of follow-through on the part of pediatricians, the perception that the infant was not in need of an evaluation, or referral to different organizations. University institutional review board rules restricted a complete evaluation of these possibilities. Finally, the success of such a program can only truly be evaluated if children are tracked until a much older age, such as school age, so long-term follow-up of the sample will be important. This will allow for not only a reexamination of diagnosis but also the opportunity to look for early predictors of long-term clinical outcome.
Despite these hurdles and unknowns, this screening program is promising because it can be implemented at virtually no cost to pediatric practices and is easily translatable into clinical practice. Consistent with other studies,30
we did note a high parental refusal rate to initiate testing and treatment once a toddler was identified by use of the screening. Thus, future effort should be placed on more clearly identifying and attempting to modify factors relating to compliance.
At a theoretical level, it is provocative to consider that programs such as the 1-Year Well-Baby Check-Up Approach that target the detection and treatment of pediatric disorders before the establishment of mature brain circuitry, have the potential to positively impact outcome for affected children. Although it is impossible to determine whether the five toddlers who no longer met criteria for having an ASD after early treatment were impacted by the potential intervention or merely had false-positive results, a comprehensive examination of the early treatment literature concluded that starting treatment as early as possible contributes to more efficacious potential interventions.32
As such, any screening program that aims to identify toddlers at risk and thus begin treatment around the first birthday at least offers the opportunity for significant gains to be made.