Over the last decade or more, besides an increased prevalence of autism diagnoses, the rate of associated Intellectual Disability (ID) tended to decrease.
Among Autism Spectrum Disorders (ASDs), IQ was found to be a strong predictor of short- and long-term outcomes, such as a potential moderator of response to treatment strategies. Thus, a specific assessment of cognitive functioning, as soon as possible, should be rigorously performed to obtain an appropriate evaluation of ASD subjects. Unfortunately, in the clinical practice, administering IQ tests can be difficult and potentially result in lower scores due to the typical clinical phenotype and behavioral problems. In young ASD children, the Psychoeducational Profile-3 (PEP-3) represents the most useful and manageable tool for the assessment. Building on existing literature, although most studies to date have been cross-sectional, PEP scores were found to be related to IQ levels; thus, developmental profile could be used to estimate cognitive functioning of preschooler children with ASD, but referring to a single point-in-time.
Therefore, even if cross-sectional studies can be extremely useful for generating hypotheses, these hypotheses need to be further confirmed by longitudinal investigation.
Objectives:
Our aim was to evaluate the longitudinal cognitive profile from the first evaluation to IQ assessment, addressing three questions: 1) At each time point, does the ASD group show a different developmental profile compare to typically-developing? 2) Is there one or more PEP domains at the first time point related to final IQ level? 3) What is the prevalence of ID in our ASD sample?
Methods:
61 ASD and 18 Typically-Developing (TD) matched children were assessed at 3 time points, each 12-24 months apart (mean age at Time 1: ASD=3.4±0.2 years; TD=4.1±0.4 years). ASD subjects were diagnosed using ADI-R and ADOS-G. No differences were detected on treatment strategies among ASD. PEP-3 (T1 and T2) and Leiter-R (T3) were administered to all participants.
Results:
T1: All PEP-3 domains exhibited a greater developmental delay in ASD compared to TD, also distinguished for typical disharmonic profile that showed expressive language, visual-motor imitation and social reciprocity as areas of weakness.
T2: On gross motor, visual-motor imitation and affective expression subtests no significant differences were observed between ASD and TD.
All PEP-3 domains at T1 not revealed significant correlation with Leiter-R IQ at T3.
In our sample of ASD, the prevalence of ID was 29% (mean IQ=88.9±15.7).
Conclusions:
Although, at baseline our data confirm a greater developmental delay (also on cognitive domain) in all ASD children, only the 29% of these subsequently shows an intellectual disability. Moreover, no correlation between PEP-3 scores and IQ levels was detected; thus, a developmental delay should not be used to predict lower IQ level.
Finally, a better understanding of the cognitive level may not only have positive implications for an early diagnosis but also for intervention and long-term outcome, as well as to differentiate cognitive phenotypes in the clinical research.
See more of: Clinical Phenotype
See more of: Symptoms, Diagnosis & Phenotype