Thinking about ‘Dose’ and SLP Practice: Part III

Continuing my discussion about the concept of ‘dose’ as applied to speech therapy, I finally get to the heart of the matter which is the issue of the optimal ‘dose’ of speech therapy to achieve the desired outcome which in our context is generalization of a phonology goal to untreated words. In previous blogs I discussed the definition of ‘dose’ in terms of the number of effective teaching episodes and the need to identify the effective ingredients of your intervention beyond the therapeutic alliance. Here I will discuss ‘dose’ specifically, as in how many effective teaching episodes are enough to achieve a good outcome in phonology intervention?

Let’s begin by returning to the pharmacology context from which the concept of dosage is borrowed. How is the concept helpful to physicians? First, it is important to know the optimum dose (or dose range) for average patients so as to avoid harming the patient. If the prescribed dose is too low the patient may not improve and the continuance or worsening of symptoms and disease will be harmful for the patient. If the dose is too high the medication itself may be toxic and harm the patient directly. Second, the patient’s response to the medication is diagnostic. If the maximum safe dosage has been prescribed and the patient is not responding favorably the physician must seek the reason: Is the patient complying with the prescribed treatment regimen? Is the patient doing something else that interferes with the effectiveness of the medication? Is the health care system administering the dose as prescribed? Does this patient respond to medications in an individualized fashion, such that a switch to another medication is required? Is the diagnosis wrong such that an entirely different treatment is called for? I will describe the research on appropriate dose in the case of meaningful minimal pairs therapy (applied to preschool aged children with moderate or severe phonological disorders) and we can consider whether these questions are relevant in the speech therapy context.

The method of meaningful minimal pairs is a uniquely linguistic approach to therapy that has the goal of changing the child’s production of an entire sound class. The procedure has two key components: (1) teaching the child pairs of words that differ by a single phoneme; and (2) arranging the environment so that the child experiences a communication breakdown if both words in a  pair are produced as a homophone. (SLPs and researchers usually get the first part right but often forget the second!) The method is directed at the child’s phonological knowledge and therefore should not be applied until after phonetic knowledge of the contrasting phonemes in the perceptual and articulatory realms has been established.

There is a lot of research involving this method and at least two papers have carefully documented the dose that leads to generalization from trained to untrained words/targets. More than 50% generalization is the outcome of interest because we know from other studies that you can discontinue direct treatment on the target pattern at this point and the child will continue to make spontaneous gains. The two papers that I will discuss have the further benefit of allowing the reader to count the “dose” precisely as the number of practice trials. The papers also provide information about the number of sessions and the number of minimal pairs over which the practice trials were distributed.

Weiner (1981) demonstrated that the method was effective with two children, using a multiple baseline design and treating deletion of final consonants (DFC), stopping of fricatives (ST) and fronting (F). Four minimal pairs were taught per target pattern and use of the pattern was probed continuously for treatment words and on a session-by-session basis for generalization words. The results do not show that much difference across target patterns but the response across children was markedly different with one child showing much faster progress than the other for all targets. For example, Child A reduced DFC to below 50% in treated words after 120 practice trials and in generalization words after 300 trials. On the other hand, Child B required 200 and 480 trials respectively to reach the same milestones for DFC. Furthermore Child A was able to accomplish many more trials in a session (e.g., 400 practice trials over 5 sessions for child A or 80 trials/session vs. 570 practice trials over 13 sessions or 43 trials/ session for child B). Despite this large variance in rate of progress across children, the study suggests that an SLP should expect a good treatment response with this method after no more than 500 trials.

This finding was replicated in a larger sample (n = 19) by Elbert, Powell and Swartzlander (1991). In this study a behaviorist approach was taken to the treatment of the minimal pair words in contrast to Weiner’s procedure that emphasized the communication breakdown as an important part of the procedure. The children were taught one pair at a time in series and the study was structured to determine how many children would achieve generalization to untreated words ,at a level of at least 50%, after learning 3, 5 or 10 pairs of words. They found that 59% of the children generalized after learning 3 pairs which took an average of 487 practice trials (range 180 to 1041) administered over approximately 5 20-minute treatment sessions; 21% of children needed to learn 5 word pairs (1221 practice trials on average) and 14% needed to learn 10 words pairs (2029 practice trials on average) before generalization occurred. This left 7% of children who did not generalize at all.

How can we use these data about dosage in our treatment planning? There is a lot of useful information here. First, we know that it is possible to achieve 80-100 practice trials in 20 minutes. Therefore, if your treatment sessions are 20 minutes long you can target one phonological pattern and if they are 60 minutes long you can target 3. Second, they show us that children do not usually generalize in under 180 practice trials (and I would argue that the data indicate that it is number of practice trials rather than sessions that is important). What harm might arise if you provide a child with the government mandated 6 annual treatment sessions, targeting three patterns, but failing to achieve more than 100 practice trials for each target pattern across the 6 sessions? We can predict that the child will not start to generalize before the end of the block and therefore will not continue to make spontaneous gains after treatment stops. When the next block begins the child may be discouraged and less cooperative with the next SLP. The parent may become discouraged and seek out complementary or alternative interventions that are even more useless or harmful than speech therapy provided with insufficient intensity!

What if the child has achieved more than 500 practice trials and has not generalized? At this point you have more than enough reason to reassess your diagnosis and/or your approach. Child B in Weiner’s study for example did finally achieve many practice trials but did so slowly because he was unable to achieve the recommended intensity, producing much fewer than 80 practice trials per session. This child also failed to generalization after 500 trials for one of his targets. Perhaps this child was lacking in the necessary prerequisites such as stable perceptual and articulatory representations for the target phonemes. Or, perhaps the child viewed the communication breakdowns to be the SLP’s listening problem rather than his own speech problem and thus a disconnect at the level of the therapeutic alliance was hampering the child’s learning.  What about the children in Elbert et al who did not generalize at all? It was eventually revealed in the paper that these children presented with many “soft signs” indicative of both speech and oral motor apraxia. Therefore, continuing to almost 3000 practice trials for these children was most assuredly harmful, given that they were not benefiting from the approach and they were deprived of the opportunity to experience a treatment approach better suited to their needs.

I am hoping that this example in the specific context of minimal pairs intervention demonstrates that the concept of dosage can be very useful in speech therapy. We need much more research that establishes typical ranges of ‘dose’ for optimum outcomes for any given intervention procedure that we use. Then we need to track these dosages as we apply procedures in our interventions. It is important to remember that the dose is not the number of sessions or visits by the child or family to the SLP. Rather, the dose is number of learning opportunities experienced by the child. When the child is not learning and we know the child has experienced the optimum dose of practice trials, we can adjust our intervention procedures with greater confidence. We can also set evidence based goals for our clients and document objectively their progress with respect to these expectations. In addition to these benefits for individual clients, this kind of information will allow us to evaluate the efficacy of our service at the program level with an objectivity that is currently lacking. Imagine if a government or an insurance company suggested that they save money by reducing the dose of our medications below effective levels! We should not allow this solution to be proposed to reduce the cost of speech therapy services. The only way to protect ourselves and our clients is with more research and greater specificity about how our treatments work. We must know the right dosage.


Thinking About ‘Dose’ and SLP Practice: Part II

I have been talking about whether it is helpful to think about dose-response relationships as an important aspect of treatment efficacy. During a recent @wespeechies exchange, we discussed whether this “medical” concept should be applied to speech therapy. One objection raised was the idea that treatment efficacy is “all about relationships” and therefore the dosage of specific inputs was not all that relevant to outcomes. In psychotherapy, objections to manualized care protocols that prescribe specific procedures for defined cases are also based on the notion that treatment efficacy is determined not by the specific ingredients of the treatment program but rather by common factors, as I discussed in a previous blog. One of the important common factors is the therapeutic alliance. How important is the therapeutic alliance to treatment outcomes? And does attention to the therapeutic alliance preclude thinking carefully about which procedures to use in which amounts with a given case?

In psychotherapy the therapeutic alliance is defined “as agreement on the goals and tasks of therapy in the context of a positive affective bond between patient and therapist.” Even when working with children, this can be an important aspect of the treatment program. For example, McCormack, McLeod, McAllister and Harrison describe children’s experience of speech impairment in a paper entitled “My Speech Problem, Your Listening Problem, My Frustration…”. This qualitative study illuminates multiple facets of an SSD and further shows that the child’s perspective and the adult’s perspective on the problem and the solution are often not aligned. Shifting the child’s attention to the role of his or her speech problem in communication breakdowns will require a genuine, caring, sensitive and trusting relationship between SLP and child. Establishing common goals and motivating the child to try new tasks to achieve those goals will also be highly dependent upon the therapeutic alliance between child and therapist.

To understand how the therapeutic alliance impacts on therapy outcomes we must return to the psychotherapy literature because I am aware of no scientific studies in the speech therapy arena that have addressed this issue directly. In mental health services, the strength of the therapeutic alliance is measured by asking clients questions about their relationship with their therapist in three domains, specifically goals (e.g., We agree on what is important for me to work on.), tasks (e.g., I agree the way we are working on my problem is correct), and bond (e.g., I believe my therapist likes me).  Very large sample studies have shown that the relationship between therapist and client accounts for about 20% of variance in outcomes. However, the relationship between outcomes and the therapeutic relationship is reciprocal: if the client gets better, they have more trust in the therapist’s guidance regarding goals and tasks. Therefore, the therapeutic relationship is theoretically independent of the techniques and procedures that the therapist uses, but in practice these variables may be related.

To put this in the speech therapy context again, Francoise Brosseau-Lapré and I are in the process of publishing the results of our RCT, Essai Clinique sur les Interventions Phonologique. We found that an input oriented approach (procedures focused on perceptual and phonological knowledge with very little articulatory practice) was as effective as an output oriented approach (all procedures focused on articulation practice) for improving children’s articulation accuracy.  Therefore, when working with a very shy child who does not like to imitate or indeed, talk at all, during speech therapy, you and the parent and the child might all agree that the input oriented approach is the ideal way to work on the child’s speech problem. Initially the therapeutic alliance might be high but what if the implementation of the approach is not competent? We find for example that it is actually quite difficult to teach students to implement the procedures (focused stimulation, error detection tasks and meaningful minimal pairs procedures) correctly. Furthermore we found that when procedures are mixed and matched in a way that is not theoretically coherent (for example, input oriented procedures in the clinic but an output oriented home practice program), we observed very poor outcomes. It is probable that in cases of poor implementation, outcomes and the therapeutic alliance will both suffer. At the very least, as I have found previously, parents are able to identify poor speech outcomes in their children even as they report good relationships with their child’s SLP.

This discussion reminds me of a very interesting article about teacher effectiveness that was circulated on twitter by @KevinWheldell. Gregory Yates makes the distinction between good teachers and effective teachers. Similarly SLPs may be readily judged to be good on the basis of personal and moral qualities such as warmth, caring, friendliness and conscientiousness, all of which contribute to positive relationships with clients, coworkers and their institution. Effectiveness requires the skillful application of specific techniques and procedures in relation to client needs however and can only be measured in reference to client outcomes. More about this in the next blogpost in this series.