Telescoping of caregiver report on the Autism Diagnostic Interview--Revised.

Since autism was introduced to the Diagnostic and Statistical Manual of Mental Disorders (DSM) in 1980 and the International Classification of Diseases (ICD) in 1977, ages of developmental milestones and onset of symptoms have been fundamental to its diagnosis. This information is often obtained retrospectively from caregiver report. Methodological issues associated with retrospective report have significant implications for diagnostic practices. The current study investigates how forward telescoping (i.e., the tendency to report events as having occurred more recently in time than they actually occurred; Sudman & Bradburn, 1973) may impact retrospective reports made by caregivers of children with autism spectrum disorders (ASD). Current DSM-IV-TR (American Psychiatric Association, 2000) criteria for a diagnosis of autistic disorder (AD) or pervasive developmental disorder – not otherwise specified (PDD-NOS) require that delays or difficulties in social, communication, or play skills are present before 3 years of age. Delay of spoken language (e.g., use of single words after 2 or phrases after 3 years) is also used to rule out Asperger’s syndrome (AS), which requires that a child not have a clinically significant language delay. Recommended revisions for DSM-5 call for a single category of ASD to subsume previously differentiated AD, PDD-NOS and AS and for the replacement of the specific age of onset criterion with a general statement that ‘symptoms must be present in early childhood’ (American Psychiatric Association, 2010). A substantial body of research has questioned the degree to which clinical presentation differs between AD, PDD-NOS and AS and whether language delay should be used to differentiate these diagnoses (see Bennett et al., 2008). Studies of young children suggest that those with a history of language delay or deviance have more severe autism symptoms (Eisenmajer et al., 1998; Gilchrist et al., 2001; Szatmari, Archer, Fisman, Streiner, & Wilson, 1995). However, when current language level is controlled, most studies including older children, adolescents and adults do not support the association between language history and symptom severity (Eisenmajer et al., 1998; Gilchrist et al., 2001; Howlin, 2003; Prior et al., 1998). Recently, directly assessed grammatical abilities at 6–8 years of age were found to be more predictive of later outcomes than diagnoses based upon caregiver-reported milestones at ages 4–6 (Bennett et al., 2008). Inconsistent results from genetic studies of ASD also call into question whether distinct categories of ASD truly exist and whether language delay is a relevant marker for making such distinctions. Some genetic studies have attempted to reduce biological heterogeneity by limiting samples to individuals with narrowly defined AD, excluding ‘milder’ cases with PDD-NOS or AS (e.g., Shao et al., 2002). Others have used language milestones to stratify samples or as endophenotypes to identify quantitative trait loci (see Losh, Childress, Lam, & Piven, 2008 for review). These approaches have yielded some promising results; however, replication in independent samples is rare (Abrahams & Geschwind, 2008). This could be due to associations between retrospectively reported ages of language acquisition and other psychometric and demographic variables, such as IQ (Hus, Pickles, Cook, Risi, & Lord, 2007), or methodological issues, such as biases associated with caregiver recall. Caregiver report is known to be influenced by many factors. For example, after a child has received a diagnosis of ASD, caregivers may tend to endorse behaviors, such as language delay, that are consistent with their child’s diagnosis (Zwaigenbaum et al., 2007). Retrospective events may also be impacted by telescoping (Sudman & Bradburn, 1973). Telescoping is influenced by the amount of time between the event and the time of reporting, the interviewer’s wording of a question, as well as the informant’s emotional state (Barsky, 2002). Some suggest that telescoping results from a compression of the timescale, in which informants systematically ‘move’ events forward in time when asked to recall when they occurred (e.g., Neter & Waksberg, 1964). Others show that telescoping can also result from more distant events being recalled with greater error than more recent events (i.e., heteroscedastic random measurement error; Pickles, Pickering, & Taylor, 1996). How onset of an event is operationalized may also play a role (Pickles et al., 1998). For example, although the child’s first spoken word is considered a discrete event occurring on a specific date, what constitutes a word to caregivers may vary across time. When children are very young, approximations supported by context may be interpreted as first words (e.g., ‘ba’ while reaching for a bottle). In older children, however, first words may be recalled as the first time each syllable of a word was clearly enunciated (e.g., ‘bottle’). Furthermore, delays in other areas of the child’s development may make it difficult for caregivers to accurately recall the true ages at which specific skills were acquired. Telescoping impacts both parent- and self-report and has been widely documented in retrospective recall of many types of events. Caregivers of children with externalizing or depressive disorders reported that their child’s symptom onset occurred 6–18 months later than indicated when interviewed five years before (Todd, Huang, & Henderson, 2008). Comparisons of retrospectively reported developmental milestones in typical children were often recalled by caregivers as having occurred earlier than originally reported (i.e., backward telescoping; Donoghue & Shakespeare, 1967; McGraw & Molloy, 1941). Majnemer and Rosenblatt (1994) suggested that telescoping varied depending on the milestone the parent was asked to recall. In their study, 91% of caregivers recalled age of first steps within two months of the originally reported age. However, only 59% reported word acquisition within two months of the original report; 20% of caregivers reported ages that were between 6 and 25 months later than first indicated (i.e., evidence for forward telescoping). Although all children were originally reported to have acquired words prior to 16 months, based on ages of language acquisition provided when the children were 3 and 5 years old, many would have been suspected of having had early language delays. Consistent with other studies (Neligan & Prudham, 1969), greater differences were associated with lower developmental and cognitive test scores. Earlier informal analyses of children with ASD or developmental delays (a subset of the present sample) suggested evidence of telescoping of language milestones from age 2 to 5 (Lord, Shulman, & DiLavore, 2004). The present study explores the potential effects of telescoping on reported ages of developmental milestones provided by caregivers of children referred for possible ASD or developmental delays prior to 3 years of age. It was hypothesized that, over time, caregivers would report later ages of concern and milestone acquisition (i.e., forward telescoping) and that telescoping of language milestones would result in an increase in the proportion of children meeting criteria for language delay. Because a clinician’s overall impressions of the presence of early developmental abnormalities is pertinent to diagnosis and relies on caregiver report, interviewers’ judgments of age of symptom onset were also examined.