PDDBI and ADOS-2 autism severity scores are correlated but yield discrepant levels of severity across assessment sites

Abstract

BackgroundPrevious studies have indicated significant associations between the severity of PDDBI composite T-scores and ADOS severity. However, significant correlations do not necessarily indicate similar absolute levels of severity which can vary with informants and with how cases are ascertained across diagnostic sites. MethodsThe relationships between the Comparison Score (CS) measure of autism severity from the ADOS-2 and Composite T-scores from the PDD Behavior Inventory (PDDBI) were examined across parent and teacher informants from cases seen at a tertiary diagnostic center (n = 157) and, for parent informants, an additional site - a diagnostic/treatment center (n = 104), which provides services that attracted cases with comorbid medical and behavioral concerns. ResultsAcross informants, CS scores were more strongly correlated with the PDDBI composite scores assessing social communication abilities (EXSCA/C) and overall autism severity (AUTISM/C) than with the composite score assessing repetitive and ritualistic behaviors (REPRIT/C) with mean severity levels of REPRIT/C and AUTISM/C slightly, but significantly, higher for teachers. Across centers, correlations between PDDBI composite scores and CS were very similar. However, while average CS scores were more severe at the tertiary center, PDDBI AUTISM/C scores were more severe at the diagnostic/treatment center solely due to higher REPRIT/C severity T-scores, likely related to their greater rates of comorbid issues. ConclusionsThese results indicate the importance of using a variety of assessment tools when making diagnostic and treatment decisions and assessing outcome with repetitive and ritualistic behaviors particularly sensitive to ascertainment factors.