Sunday, 23 February 2020

Changing terminology for children's language disorders: reflections on special issue of Perspectives of the ASHA Special Interest Groups

In 2016-7, I joined with expert colleagues to try to tackle the thorny issue of terminology for children who had difficulties speaking or understanding in their native language. This was incredibly challenging: we had a panel of 57 experts, moderated by Maggie Snowling and me, engage in a Delphi process, whereby we iteratively rated and commented on statements to do with identification and diagnosis to converge on a set of recommendations (Bishop et al., 2016; 2017). There was substantial disagreement between experts, who came from a range of disciplines and nationalities, but the one thing we agreed upon was that the current situation – of a plethora of different terms being used with various meanings – was doing a grave disservice to families and their children affected by language problems. There was a lack of recognition of language problems among professionals and the general public, as well as a paucity of research relative to other conditions of similar severity and prevalence. Eventually we converged on a recommendation that the term 'Developmental Language Disorder' (DLD) should be used to describe children with persistent problems with language expression or reception that had no obvious cause, and that impacted on everyday life.

Publication of the 2017 recommendations had considerably greater impact than I had anticipated, thanks to the generally enthusiastic take-up of the new terminology, which has been adopted by professional organisations in the UK, Ireland and Australia. A brief summary of the salient points was written by Susan Ebbels for the Royal College of Speech and Language Therapists.

Following the publication of the CATALISE papers, big changes have happened just in a couple of years:
  • The terminology has stimulated development of grassroots advocacy, with campaigns to promote awareness of DLD adopting ingenious and innovative methods to publicise events. See e.g. here.
  • The DLD label has raised awareness that this is a life-long condition*. Adults with DLD have started to talk about their experiences on social media (e.g. here). 
  • Figures on terminology from Web of Science show that DLD is starting to overtake the term 'Specific Language Impairment' in published papers.
     
  • Figure 1: N publications with full term 'Specific Language Impairment' or 'Developmental Language Disorder' in the Topic field; data from Web of Science

    Nevertheless, despite these positive developments, not everyone has been convinced that adoption of DLD is a good thing. This is not surprising: a couple of years ago, I reflected on some of the reasons why this particular topic is a terminological minefield (Bishop, 2017). It is difficult to balance the pros and cons of new terminology, especially when one is dealing with a condition that is heterogeneous, changes with age, can co-occur with many other problems, and is of relevance to several professions with very different perspectives, in particular speech-language therapists/pathologists, educators and medics.

    Resistance to new terminology appears to be strongest in the USA, with the American Speech-Language-Hearing Association being particularly cautious about replacing the term Specific Language Impairment with DLD. This week they published a set of papers by individuals with different viewpoints on the topic, and reading through this I was reminded of many of the debates we had in the course of our Delphi exercises. The special issue includes a  tutorial overview by Karla McGregor and colleagues (McGregor et al., 2020), who summarise the background to the CATALISE project, and subsequent developments. They are supportive of DLD, not least because of the way the new terminology has boosted the profile of children's language problems and stimulated greater efforts towards advocacy. But we need to take seriously the concerns of those who have doubts.

    Two authors in particular, Larry Leonard and Mabel Rice, were concerned that if we adopt DLD as the preferred term, decades of research on SLI would be ignored and ultimately forgotten. Both of them have made major lifetime contributions to the field, and so their concerns are understandable. It is vital that we heed Larry's advice (Leonard, 2020) to ensure that we include the search term SLI as well as DLD when drawing together relevant literature, to ensure valuable work from previous decades is not lost.

    A related issue is that, although they overlap, SLI and DLD are not identical. In general, DLD is a more inclusive term, as it does not require that nonverbal IQ is 85 or over (although it does exclude cases of intellectual disability**), and it is compatible with the presence of other neurodevelopmental disorders, especially developmental co-ordination disorder and attention-deficit-hyperactivity disorder. Rice (2020) remains strongly opposed to the use of DLD, mainly because this would entail including children with nonverbal IQs below 85 (who were termed cases of nonspecific language impairment, or NLI, in a big epidemiological study, the Iowa study). Yet this stance is hard to reconcile with her view that nonverbal ability is independent of language. She spends several paragraphs presenting evidence that it is possible to have low nonverbal ability and good language, or high nonverbal ability and poor language, culminating in the statement: 'The common assumption that children with SLI are not very smart is unwarranted, as is the assumption that all children with strong language aptitude are smart.' It is unclear to whom she is referring as making this 'common assumption'. A major reason why the CATALISE group decided to drop 'cognitive referencing' in defining DLD was because the bivariate distribution of nonverbal IQ and language demonstrates rather a weak association – just as she claims - but this makes it clear that any division into those above and below an IQ threshold is arbitrary (see Figure 2). Just to be absolutely clear, in proposing we do away with nonverbal IQ criteria for DLD, the CATALISE consortium were not saying that children with SLI are 'not very smart'. We were saying that they key thing is what your language is like, and that nonverbal ability is largely irrelevant when making that judgement.
Figure 2: Language composite measure plotted against non‐verbal IQ for 603 eight‐year‐old children in the Iowa study. Figure from Reilly et al (2014). Blue points correspond to SLI, and green points to NLI. NB Axes resized to address criticism by Rice (2020), who found the scaling misleading.

    Rice goes on to argue that we need to study children's mastery of specific grammatical markers over time to get a precise measure of children's language in SLI, yet she then goes on to present data showing that children with NLI are also identified by low scores on those markers. Although she claimed a difference in language profiles, this was not evident from the data she presented, and in general, most studies that have looked for qualitative differences between NLI and SLI have failed to find these (see also further evidence from McGregor et al, 2020). Rice maintains that only by sticking with SLI would we find sufficiently clear findings to advance our understanding, and that if we adopt less precise categories, this will lead to muddying of the waters and less replicable results. I regard this as a hypothesis that can be tested, but for which there is currently no good evidence. In fact, it was the failure to find such evidence in my own studies 25 years ago that led me to start to question the construct of SLI (Bishop, 1994).

    Larry Leonard makes the sensible suggestion that if we study DLD we should also provide data on which children would meet the more restrictive definition of SLI:  this would, in fact, allow us to test Rice's hypothesis. The best way to do this, and to build on prior studies with SLI would be to make raw data open (see Meyer, 2018), so that results can be analysed to investigate the extent to which findings depend on levels of nonverbal ability, attention, motor skills and so on. There is already precedent for this with the EpiSLI database from the Iowa study (Tomblin, 2010) – this includes data on children who would meet broader DLD criteria as well as more selective SLI cases. This way we could investigate empirically the impact of the choice of criteria, rather than just asserting that one classification approach is better than the other.

    I turn next to the other commentary that is predominantly negative about a change of criteria to DLD, that by Murza and Ehren (2020). Their perspective is diametrically opposed to that of Rice. They explain that for speech-language pathologists (SLPs) working in the school system, there is a mismatch between what is taught in their university courses (including diagnosis of SLI) and what they experience in the classroom. There were some parallels here with the views of education experts on the CATALISE panel, some of whom felt the whole debate about labels was irrelevant, and would empathise with the view that: 'No matter the label, students should receive the services they need, and no label should drive services'. But, as Murza and Ehren recognise, labels are needed to demonstrate eligibility for services, and in the USA, this is determined by the Individuals with Disabilities Education Act (IDEA), which has its own set of labels: these don't include either SLI or DLD. I felt a sense of despair coming through from this article, as the authors documented the confusing array of possible terms they could use, each of which had an operational definition, but with that definition varying from one state to another. The impression was that SLPs in US education are up against a massive, unbending bureaucracy that they had to negotiate in order to deliver services to a subset of the children that might benefit from them. In principle, yes, it would be nice to have some consistent terminology that mapped on to the population they were serving, but their conclusion was that they lacked the time, money, energy and focus to embark on a campaign to adopt new labels. This was a considerably more sober and downbeat chapter than that of Rhea Paul, who regarded DLD as potentially compatible with IDEA criteria, and a useful focus for advocacy efforts. 

    When discussing relevance of labels for SLP practitioners, another issue concerned insurance eligibility. Karla McGregor reported that she had been told by an insurer: 'If a child just isn't talking or not talking clearly - it is not covered'. The authors also noted a common concern that the term Developmental would be interpreted by insurers, and perhaps others, as implying that the condition would improve of its own accord. But SLPs should not take these kinds of responses lying down: it is grossly inequitable if insurers are willing to pay for a condition such as ADHD or Developmental Co-ordination Disorder, but not for speech-language therapy for a child with DLD. The arguments can and should be made, and it is hoped that the growing awareness of, and advocacy for DLD will empower US SLPs to be more proactive in demanding that children with language disorders are taken seriously and given the support they need.

    * Damian Quinn, a man with DLD, has written an autobiography. The timing in relation to CATALISE is probably co-incidental, but this will help with growing awareness that children with DLD do not disappear when they become adults!

    ** The introductory article for the special issue stated that DLD is used for children 'with or without intellectual disability'. This is wrong. Where the child meets criteria for intellectual disability, the diagnosis would be Language Disorder associated with Intellectual Disability.


    P.S. (24 Feb 2020). All the materials from the CATALISE project, including anonymised ratings and comments from the 57 panel members, are available on Open Science Framework.

    References
     Bishop, D. V. M. (1994). Is specific language impairment a valid diagnostic category? Genetic and psycholinguistic evidence. Philosophical Transactions of the Royal Society, series B, 346, 105-111. 
    Bishop, D. V. M. (2017). Why is it so hard to reach agreement on terminology? The case of developmental language disorder (DLD). International Journal of Language & Communication Disorders, 52(6), 671-680. doi:10.1111/1460-6984.12335

    Bishop, D. V. M., Snowling, M. J., Thompson, P. A., Greenhalgh, T., & CATALISE Consortium. (2016). CATALISE: a multinational and multidisciplinary Delphi consensus study. Identifying language impairments in children. . PLOS One, 11(7), e0158753. doi:doi:10.1371/journal.pone.0158753

    Bishop, D. V. M., Snowling, M. J., Thompson, P. A., Greenhalgh, T., & CATALISE Consortium. (2017). Phase 2 of CATALISE: a multinational and multidisciplinary Delphi consensus study of problems with language development: Terminology. Journal of Child Psychology and Psychiatry, 58(10), 1068-1080. doi:10.1111/jcpp.12721

    Leonard, L. B. (2020). A 200-year history of the study of childhood language disorders of unknown origin: changes in terminology. Perspectives of the ASHA Special Interest Groups, 5(1), 6-11. doi:https://doi.org/10.1044/2019_PERSP-SIG1-2019-0007

    McGregor, K. K., Goffman, L., Owen Van Horne, A., Hogan, T. P., & Finestack, L. H. (2020). Developmental Language Disorder: Applications for advocacy, research, and clinical service. Perspectives of the ASHA Special Interest Groups, 5(1), 38-46. doi:https://doi.org/10.1044/2019_PERSP-19-00083

    Meyer, M. N. (2018). Practical tips for ethical data sharing. Advances in Methods and Practices in Psychological Science. doi:https://doi.org/10.1177/2515245917747656

    Murza, K. A., & Ehren, B. J. (2020). Considering the language disorder label debate from a school speech-language pathology lens. Perspectives of the ASHA Special Interest Groups, 5(1), 47-54. doi:https://doi.org/10.1044/2019_PERSP-19-00077

    Paul, R. (2020). Children's language disorders: What's in a name. Perspectives of the ASHA Special Interest Groups, 5(1), 30-37. doi:https://doi.org/10.1044/2019_PERS-SIG1-2019-0012
    Rice, M. (2020). Clinical lessons from studies of children with Specific Language Impairment. Perspectives of the ASHA Special Interest Groups, 5(1), 12-29. doi:https://doi.org/10.1044/2019_PERSP-19-00011

    Reilly, S., Tomblin, B., Law, J., McKean, C., Mensah, F. K., Morgan, A., . . . Wake, M. (2014). Specific language impairment: a convenient label for whom? International Journal of Language & Communication Disorders, 49(4), 416-451. doi:10.1111/1460-6984.12102

    Tomblin, J. B. (2010). The EpiSLI database: a publicly available database on speech and language. Lang Speech Hear Serv Sch, 41(1), 108-117.

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