LAY ABSTRACT Measuring the severity of autism is a challenge for researchers and clinicians. Recently, Gotham et al., (2009) addressed this issue by creating calibrated severity scores (CSS) based on raw total scores of the Autism Diagnostic Observation Schedule (ADOS), a standardized measure commonly used in autism diagnosis. We tested the utility of the CSS by comparing its scores to raw scores from the ADOS in a sample of 368 children aged 2–12 years with autism, PDD-NOS, non-spectrum delay, or typical development. As expected, we found that the CSS were more uniformly distributed within diagnostic categories and across ADOS modules than were raw scores. In particular, CSS were useful in controlling for differences in verbal development. Follow-up evaluations showed good temporal stability of the CSS over 12–24 months in children with autism. The results of this study support the use of the CSS to measure the severity of the core symptoms of autism. Further research is needed to determine if the CSS can also be used to measure changes in symptom severity and serve as a tool for clinical research. SCIENTIFIC ABSTRACT Measurement of the severity of autism at a single time point, and over time, is a widespread challenge for researchers. Recently, Gotham et al., (2009) published a severity metric (calibrated severity scores; CSS) that takes into account age and language level and is based on raw total scores of the Autism Diagnostic Observation Schedule (ADOS), a standardized measure commonly used in autism diagnosis. The present study examined psychometric characteristics of the CSS compared to raw scores in an independent sample of 368 children aged 2–12 years with autism, PDD-NOS, non-spectrum delay, or typical development. Reflecting the intended calibration, the CSS were more uniformly distributed within clinical diagnostic category and across ADOS modules than were raw scores. Cross sectional analyses examining raw and severity scores and their relationships to participant characteristics revealed that verbal developmental level was a significant predictor of raw score, but accounted for significantly less variance in the CSS. Longitudinal analyses indicated overall stability of the CSS over 12–24 months in children with autism. Findings from this study support the use of the CSS as a more valid indicator of autism severity than the ADOS raw total score, and extend the literature by examining the stability over 12–24 months of the CSS in children with ASD.

Estimates of intelligence in young children with neurodevelopmental disorders are critical for making diagnoses, in characterizing symptoms of disorders, and in predicting future outcomes. The limitations of standardized testing for children with developmental delay or cognitive impairment are well-known: tests do not exist that provide developmentally appropriate material along with norms that extend to the lower reaches of ability. Two commonly used and interchanged instruments are the Mullen Scales of Early Learning (MSEL), a test of developmental level, and the Differential Ability Scales, 2nd Edition (DAS-II), a more traditional cognitive test. We evaluated the correspondence of contemporaneous MSEL and the DAS-II scores in a mixed sample of children aged 2 to 10 years with autism spectrum disorder (ASD), non-ASD developmental delays, and typically developing children across the full spectrum of cognitive ability. Consistent with published data on the original DAS and the MSEL, scores on the DAS-II and MSEL were highly correlated. However, curve estimation revealed large mean differences that varied as a function of the child’s cognitive ability level. We conclude that interchanging MSEL and DAS-II scores without regard to the discrepancy in scores may produce misleading results in both cross-sectional and longitudinal studies of children with and without ASD, thus, this practice should be implemented with caution.

The results supported the hypothesis that mothers' psychosocial functioning is significantly related to concern about child behaviour and disclosure of concerns to the paediatrician. The inability of child behaviour and maternal functioning to predict which mothers were concerned and disclosed concerns supports the hypothesis that disclosure and identification of psychosocial problems in primary care is complex and requires a multifactor model.

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