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Rehabilitation Treatment Taxonomy: Establishing Common Ground

  • Marcel P. Dijkers
    Correspondence
    Corresponding author Marcel P. Dijkers, PhD, FACRM, Department of Rehabilitation Medicine, Box 1240, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029.
    Affiliations
    Department of Rehabilitation Medicine, Icahn School of Medicine at Mount Sinai, New York, NY
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      Abstract

      This article introduces the Archives supplement presenting a conceptual framework for the creation of a rehabilitation treatment taxonomy (RTT). It describes the key theoretical and empirical articles and their role, and the commentaries that were solicited. More importantly, based on feedback received to date, it sketches what the RTT is proposed to address, and what it explicitly excludes; therefore, the readers will have appropriate expectations and criteria for what is offered.

      Keywords

      List of abbreviations:

      ICF (International Classification of Functioning, Disability and Health), RTT (rehabilitation treatment taxonomy), TBI (traumatic brain injury)
      Describing what we do always has been difficult for rehabilitation practitioners. Teaching student clinicians has been very much a hands-on experience, and rehabilitation is more lore than well-developed theory.
      • Kane R.L.
      Improving outcomes in rehabilitation. A call to arms (and legs).
      One reason for the atheoretical state of rehabilitation may be that we lack a universally accepted set of terms and concepts to talk about rehabilitation treatment, and do not have a carefully developed taxonomy of interventions that was created using these concepts. The fact that natural recovery is ubiquitous, and that getting people activated and teaching them a new routine are the commonsense reactions to what nature does not do, are the reasons theory was never seen as useful.
      The aim of this supplement is to start bringing about a change in this situation. It proposes a conceptual framework for a cross-disciplinary rehabilitation treatment taxonomy (RTT) that offers terms and concepts needed to talk about treatments, and the start of a classification. The first article by Dijkers et al
      • Dijkers M.P.
      • Hart T.
      • Tsaousides T.
      • Whyte J.
      • Zanca J.M.
      Treatment taxonomy for rehabilitation: past, present, and prospects.
      reviews the various intervention taxonomies existing in health care and the attempts at building classifications in rehabilitation. It also describes the benefits to the field of rehabilitation of a commonly accepted classification of treatments.
      This article is followed by 4 articles that set forth the key ideas in the conceptual framework that the research group (Dijkers, Ferraro, Hart, Packel, Tsaousides, Whyte, Zanca) has developed. Whyte
      • Whyte J.
      Contributions of treatment theory and enablement theory to rehabilitation research and practice.
      further develops the distinction between treatment theory and enablement theory that he first drew over 15 years ago.
      • Whyte J.
      Distinctive methodologic challenges.
      Next, Whyte et al
      • Whyte J.
      • Dijkers M.P.
      • Hart T.
      • et al.
      Development of a theory-driven rehabilitation treatment taxonomy: conceptual issues.
      present other crucial concepts in the framework, including ingredients, mechanism of action, and target of treatment. It is followed by an article by Hart et al,
      • Hart T.
      • Tsaousides T.
      • Zanca J.M.
      • et al.
      Toward a theory-driven classification of rehabilitation treatments.
      who describes that these notions set forth the idea of the tripartite structure of treatment theories and starts delineating 4 basic groupings of treatments that would seem to differ from one another in the ingredients used, the mechanisms of action engaged by those ingredients, and the aspects of functioning of patients that the mechanisms are hypothesized to change. A second article by Dijkers et al
      • Dijkers M.P.
      • Hart T.
      • Whyte J.
      • Zanca J.M.
      • Packel A.
      • Tsaousides T.
      Rehabilitation treatment taxonomy: implications and continuations.
      takes up a number of difficulties encountered when one attempts to apply the framework to actual treatments. It is strongly suggested that these 4 articles (and the glossary of terms, page A9 of this supplement, and online at http://www.archives-pmr.org/) be read as a whole. As our peer reviewers, who generally saw only one article, noted, reading only one article brings up questions that likely are answered in one of the other articles. The authors of the successive articles refer to the other articles by our group and sometimes summarize a point carefully elaborated in another article; however, in the end, reading them all as a whole is the only way of getting full exposure to the concepts being proposed.
      These articles are followed by 2 more empirical ones. Hart et al
      • Hart T.
      • Ferraro M.
      • Myers R.
      • Ellis C.A.
      Opening the black box: lessons learned from an interdisciplinary inquiry into the learning-based contents of brain injury rehabilitation.
      report on an earlier attempt to create a reliable classification of traumatic brain injury (TBI) interventions that involve patient learning and the challenges encountered in this process. These lessons were used by the present authors in developing their own framework, as were the opinions and experiences of the therapists who took part in focus groups and open-ended interviews held by Zanca and Dijkers.
      • Zanca J.M.
      • Dijkers M.P.
      Describing what we do: a qualitative study of clinicians' perspectives on classifying rehabilitation interventions.
      All of the latter clinicians had taken part in the TBI and spinal cord injury Practice-Based Evidence studies, during which they developed and/or applied ad hoc classifications of interventions commonly used with these 2 diagnostic groups.
      These articles are followed by a set of commentaries solicited from scholars with a special interest in the issue of classification, as applied to rehabilitation. Hoenig, who has previously published on the classification of rehabilitation environments,
      • Hoenig H.
      • Sloane R.
      • Horner R.D.
      • Zolkewitz M.
      • Duncan P.W.
      • Hamilton B.B.
      A taxonomy for classification of stroke rehabilitation services.
      puts the present efforts in the light of prescientific and scientific attempts to classify entities but also takes issue with a number of the decisions made by the conceptual scheme's authors, especially how environment is treated.
      • Hoenig H.
      What would Darwin say? A historical perspective on the next steps in developing a rehabilitation classification system.
      Cieza and Bickenbach
      • Cieza A.
      • Bickenbach J.
      Is a rehabilitation treatement taxonomy the right answer to the rehabilitation black box?.
      endorse the tripartite structure of treatment theories but question whether it is even possible to build an RTT deductively. They suggest that taxonomizing is/should be founded in empirical research; once rehabilitation research proceeds from the empirical evidence upward, “a classification would follow as a matter of course.”(px)
      Fasoli and Chen,
      • Fasoli S.E.
      • Chen C.C.
      What do clinicians need from a rehabilitation treatment taxonomy? An alternate approach for describing treatment content versus process.
      focusing on the Zanca and Dijkers study,
      • Zanca J.M.
      • Dijkers M.P.
      Describing what we do: a qualitative study of clinicians' perspectives on classifying rehabilitation interventions.
      discuss the advantages and, especially, the challenges of a deductive, theory-driven classification for describing the creative and complex nature of rehabilitation practice.
      In her commentary, VanHiel
      • VanHiel L.R.
      Treatment and enablement in rehabilitation research.
      focuses on the enablement theory-treatment theory distinction, and applies it to published intervention research. VanHiel finds the distinction attractive but questions the ease of applying it in practice.
      Finally, Sykes
      • Sykes C.
      Rehabilitation treatment taxonomy and the International Classification of Health Interventions.
      points out the commonalities between the conceptual framework of the RTT and the principles that underlie the International Classification of Health Interventions, currently under construction. Sykes also mentions areas where our conceptual framework and the principles of the International Classification of Health Interventions principles diverge.
      The key articles in this supplement were written, revised based on peer review, and accepted over the period of October 2012 to May 2013, and the commentaries were written and revised between February and July 2013. The peer review comments and the criticisms and suggestions in the commentaries made clear some of the shortcomings of our ideas, or at least of their presentation. This was underscored by 16 hours of spirited and collegial discussion during a workshop with some commentators and others held June 17 through June 19, 2013, in Rockville, Maryland. Ruth Brannon, MA, Mary Chamie, PhD, Alarcos Cieza, PhD, MPH, Rebecca Craik, PhD, Anne Forest, PhD, Rob Forsyth, PhD, BMBCh, MA, Allen Heinemann, PhD, Helen Hoenig, MD, MPH, John Hough, PhD, James Lenker, PhD, OTR/L, Susan Lin, ScD, OTR/L, Mary Ellen Michel, PhD, Susan Michie, DPhil, CPsychol, FBPS, AcSS, Koen Putman, PhD, Joan Rogers, PhD, OTR/L, Margaret Rogers, PhD, Monica Sampson, MA, CCC-SLP, Mary Slavin, PT, PhD, Pimjai Sudsawad, ScD, Lyn Turkstra, PhD, Mike Weinrich, MD, Nancy White, PT, DPT, OCS, Marieke van Puymbroeck, PhD, CTRS, and Carolee Winstein, PhD, PT, read the articles and commentaries then available and joined us for a free-flowing discussion of strengths and weaknesses of the conceptual framework, alternatives and extensions, and suggestions for methods in which the RTT can be developed as a resource of and for the entire field of rehabilitation.
      We took careful note of the problems they had with the terminology, the ideas they thought were ready to roll out, and the ideas they believed needed more consideration. Because terms tend to persist long after they have been found to be lacking (eg, each year there still is a handful of articles that use head injury instead of TBI), we prioritized a review of our terms and made several changes. The articles and commentaries presented here incorporate, with the permission of the editors of Archives to make post-peer review changes, the revised terminology. More substantive changes require careful consideration and tryout using real-life examples and may be presented in a future publication, along with further RTT issues and developments. It is hoped that many of these will be contributed by Archives readers who, whether they agree or disagree with us, consider a framework for a classification of rehabilitation treatments important enough to command their attention.
      For now, we want to make sure Archives readers see the RTT conceptual scheme in the right perspective. The following paragraphs are offered in an attempt to supplement or emphasize what is written in the articles.
      First, the conceptual framework limits the scope of the classification to be created to what the clinician (therapist, nurse, physician) does to and for the patient, or has the patient do. Everything else—the structure of rehabilitation (in Donabedian's terminology
      • Donabedian A.
      Explorations in quality assessment and monitoring: the definition of quality and approaches to its assessment.
      ) and all “process,” insofar as it is not therapy focused on changing the patient's functioning and personal factors (as defined in the International Classification of Functioning, Disability and Health [ICF]
      World Health Organization
      International Classification of Functioning, Disability and Health: ICF.
      )—is excluded. Our argument is that elements and processes, such as clinician expertise and interdisciplinary coordination and quality assurance efforts, may influence what is done or not done for a patient; however, only what is actually done can change the patient for the better.
      • Whyte J.
      Invited commentary on quality of care indicators for the rehabilitation of children with traumatic brain injury, and quality of care indicators for the structure and organization of inpatient rehabilitation care of children with traumatic brain injury.
      Second, the conceptual framework, illustrated in figure 1, places the therapeutic hour in the context of the entire rehabilitation enterprise. The care of the individual patient is embedded in the rehabilitation program with its structure and coordinating processes, which in turn is part of a larger health care system of care. Clinicians (potentially of many types and with diverse treatment orientations) deliver treatments 1, 2, and 3 aiming to achieve several macro outcomes—maybe self-management, physical independence, and acceptance of one's disability, in a particular case. To achieve those, they provide, after an initial assessment, the 3 treatments, confident that they will be able to bring about positive change in the 3 corresponding targets. A feedback loop and continuing assessment are used to make sure that their treatments are achieving those targets and are likely to achieve and maintain the distal outcomes.
      Figure thumbnail gr1
      Fig 1Focus of the RTT within the larger care system. Abbreviations: incl., including; Rx, treatment; Tgt, target of treatment.
      Third, the formal assessments undertaken at the start of a rehabilitation episode (admission to rehabilitation) and at interim points to reassess status and formulate new treatment goals, while crucial to the success of treatment, are not considered treatment in themselves and are excluded from the taxonomy. Their exclusion and the exclusion of the whole of clinical reasoning from the scope of a treatment taxonomy were a bone of contention both in the Zanca and Dijkers focus groups
      • Zanca J.M.
      • Dijkers M.P.
      Describing what we do: a qualitative study of clinicians' perspectives on classifying rehabilitation interventions.
      and in the workshop.
      • Fasoli S.E.
      • Chen C.C.
      What do clinicians need from a rehabilitation treatment taxonomy? An alternate approach for describing treatment content versus process.
      We assert, however, that the role of the RTT is not to describe the decision making process per se, but to provide a means of identifying and describing the treatments that result from that process so that we may better understand what clinicians do and which ones of their many treatments are effective in changing which targets.
      Fourth, similarly, the RTT does not address, and need not address, the patient and other factors that may limit the effectiveness of a particular treatment. In the ICF,
      World Health Organization
      International Classification of Functioning, Disability and Health: ICF.
      there is a formal structure available to record the strengths and weaknesses of a patient, and there is no need for the RTT to incorporate these. Clinicians know that certain physical, cognitive, social, and emotional features make the mechanism of action of particular treatment ingredients ineffectual, if not inoperable; if it is not possible to avoid these ingredients, patient characteristics may demand that they be administered over a longer time and/or in a higher dosage.
      • Fasoli S.E.
      • Chen C.C.
      What do clinicians need from a rehabilitation treatment taxonomy? An alternate approach for describing treatment content versus process.
      Similarly, the downstream effects of treatment, changes in functioning that often require more therapies to address yet other deficits a patient may have, need not be in the RTT.
      • Whyte J.
      Contributions of treatment theory and enablement theory to rehabilitation research and practice.
      (This too was debated at length in our meeting.) The ICF allows one to specify such levels of functioning, and there is no need for the RTT to duplicate the ICF, as Sykes
      • Sykes C.
      Rehabilitation treatment taxonomy and the International Classification of Health Interventions.
      notes.
      Fifth, the myriad factors in the social and physical environment of the patients' daily lives that affect their functioning are also not in the proposed RTT, for good (facilitators of the ICF) or for bad (barriers). The purpose of the RTT is to offer a terminology and a taxonomy to carefully and fruitfully describe what rehabilitation clinicians do. The other things that during or after rehabilitation influence patients' functioning need not be in the taxonomy, unless a clinician decides that changing this aspect of the person or their environment is a fruitful way of improving a particular patient's situation. In that case, there better be a category in the RTT to designate what is being done. Other than that, the conceptual scheme acknowledges the multiple influences on functioning (see fig 1 in Dijkers et al
      • Dijkers M.P.
      • Hart T.
      • Whyte J.
      • Zanca J.M.
      • Packel A.
      • Tsaousides T.
      Rehabilitation treatment taxonomy: implications and continuations.
      ) and leaves things at that.
      Sixth, our claim is that, in principle, the RTT can address the fluidity of a treatment session, with the therapist switching from one treatment that he or she claims has 2 different targets (more normative gait and correct recognition of clues to orientation in space) to a treatment with 3 targets and a different distal aim. We can dissect the treatment session and for each component determine what the ingredients are, and how they are hypothesized to make a difference in which aspects of the patient's functioning. Will we lose something because the whole is more than the parts? Yes, possibly—good therapists indeed seem to pack more into a session than they themselves realize. The RTT is not designed to encourage cookbook therapy, in spite of the term “ingredients.” Our claim is that by dissecting a treatment session we will gain something. Whenever we pay attention to what we do, how we do it, and the reasons for doing it, we gain a better understanding of our practices.
      Seventh, the fact that everything that the clinician does in direct interaction with patients (or sometimes in interaction with their social and physical environment to make those optimally accommodating) is the only thing allowed in the RTT does not mean everything else is unimportant. However, if one considers a sequence of events leading from Donabedian's structure
      • Donabedian A.
      Explorations in quality assessment and monitoring: the definition of quality and approaches to its assessment.
      through his processes to his outcomes, the focus should be on those components of processes that actually bring about changes in the patient, and optimal classification would seem to be served by focus on the immediate causes (what the clinician does for and with this patient) and the immediate outcomes (targets), rather than the more distal ones that may require other changes in the patient achieved by other therapists using other therapies, as argued by Whyte.
      • Whyte J.
      Contributions of treatment theory and enablement theory to rehabilitation research and practice.
      Eighth, we received a comment (if not accusation) from some of our Archives peer reviewers that the conceptual framework, in addition to being reductionistic, is mechanistic: ingredients cause a mechanism of action to operate, which results in changes in a target. We admit that this is a simplification if the topic of interest is the entire intricate process of rehabilitation, which should be studied using systems theory. We also acknowledge that it provides a pale reflection of the art of treatment. However, our aim never was to describe all of rehabilitation in all its intricacies; we focused on the questions How can treatments be distinguished from one another in a scientifically valid and fruitful way? and How can they be quantified so that we have better ways of describing what goes on inside the black box? Our aim was nothing more and nothing less.
      Finally, we admit that we were captives of the seductive simplicity of a Linnaean type of classification for too long, where everything fits perfectly into one and only one category, which with cognate classes can be combined into a superordinate category. This type of classification may fit perfectly for sorting physical entities (including drugs and assistive technology items, orthotics and prosthetics), but the patient-clinician actions and interactions that are at the core of rehabilitation are difficult to differentiate that way. We may need to accept the less than perfect organization that is offered by alternative ways of organizing entities (eg, as suggested by Lambe
      • Lambe P.
      Organising knowledge: taxonomies, knowledge and organisational effectiveness.
      ), and we invite readers to start thinking about how they would make finer distinctions within the 4 major treatment groupings described by Hart et al.
      • Hart T.
      • Tsaousides T.
      • Zanca J.M.
      • et al.
      Toward a theory-driven classification of rehabilitation treatments.
      In the meantime, we continue the study of ontology.
      • Hoehndorf R.
      • Dumontier M.
      • Gkoutos G.V.
      Evaluation of research in biomedical ontologies.
      This entire enterprise started out with a grant proposal to the National Institute on Disability and Rehabilitation Research in which we offered to develop a conceptual framework (then named a blueprint) for building an RTT and 2 local (partial) taxonomies (one of interventions aimed at improvements in executive functioning, the other of treatments for gait in neurologic disorders), as proof of concept for the blueprint. Developing the blueprint took longer than anticipated, and rather late we realized that in creating the 2 partial taxonomies as conceptualized we would commit the same failing we have leveled at many other rehabilitation taxonomists: naming and classifying a treatment by its presumed target.
      • Dijkers M.P.
      • Hart T.
      • Tsaousides T.
      • Whyte J.
      • Zanca J.M.
      Treatment taxonomy for rehabilitation: past, present, and prospects.
      What we now have, after many hours of discussion, is a conceptual framework, large parts of which our colleagues at the meeting in Rockville signed off on, although there were other parts that they suggested we gave a second look.
      Lastly, why publish a conceptual framework? Would it not be more fruitful to wait until a complete RTT is available, however much in beta format, and however many changes it might undergo in years to come? (The International Classification of Diseases, after all, has gone to 10 versions over more than a century, and work on version 11 is already under way before the United States officially introduces the International Classification of Diseases, Tenth Revision, Clinical Modification.) We realize that the RTT with 4 treatment groups offered here
      • Hart T.
      • Tsaousides T.
      • Zanca J.M.
      • et al.
      Toward a theory-driven classification of rehabilitation treatments.
      is not very useful in actually classifying the myriad interventions rehabilitationists of many disciplines deliver for patients of very diverse diagnostic groups. However, just as we invited a small group of colleagues in Rockville to critically look at what we were proposing, and just as we invited commentaries by people who have an interest in the issue of the classification of rehabilitation interventions, we hope that publication of our conceptual framework will occasion an expanded discussion among clinicians, educators, editors, research grant makers, administrators, and even patients about an issue that should be near at heart for all of them: describing what we do.

      Acknowledgments

      I thank Mary Ferraro, PhD, OTR/L, Tessa Hart, PhD, Andy Packel, MSPT, John Whyte, MD, PhD, and Jeanne M. Zanca, PhD, PT, for comments on an earlier version of this supplement introduction. John Whyte, MD, PhD, conceived the figure.

      Supplemental Appendix S1 Glossary of Terms.

      Active ingredients – Attributes of a treatment, selected or delivered by the clinician, that play a role in the treatment's effects on the target of treatment. These include the essential ingredients associated with the treatment's known or hypothesized mechanism of action, and any other ingredients that moderate the treatment's effect(s) but may be common to multiple treatments.
      Aim(s) (of treatment) – Aspect(s) of the patient's or other recipient's functioning or personal factors that is predicted to change indirectly (via mechanisms specified in enablement/disablement theory) as a result of the treatment-induced change in the treatment target. A single treatment may have multiple aims, and there may be a chain of treatment aims (eg, exercises leading to increased strength leading to improved ambulation leading to greater community participation) with at least 1 (in the case of treatments delivered to other recipients) involving the patient's functioning. Although highly relevant to the ultimate clinical value of a treatment, these distal treatment aims are not relevant to the definition or classification of the treatment. (As previously noted, when the target of treatment is clinically and functionally significant in its own right, we avoid calling it a treatment aim to avoid confusion about direct vs indirect effects of treatment.)
      Course of treatment – Series of treatment sessions or therapist-recipient contacts that are pursuing change in a specific treatment target, sometimes with some form of treatment progression within or between contacts.
      Dosing parameters – Quantitative variations in the strength, intensity, frequency, and/or quantity of treatment ingredients; these are often expressed as an amount of time during which the recipient is continuously exposed to the ingredient, the number of times a discrete ingredient is administered, or the magnitude of the ingredient on a quantifiable scale.
      Enablement/disablement theory – Conceptual system that specifies how change in one aspect of a patient's functioning (eg, at the level of an International Classification of Functioning, Disability and Health component: body structure, body functioning, activity/activity limitation, participation/participation restriction, personal factor, or environment) will translate into changes in another aspect, specifically a characteristic classified elsewhere in the framework being used.
      Essential ingredients (of a treatment) – Active ingredients, selected or delivered by the clinician, that define a particular treatment and distinguish it from other treatments. The essential ingredients are those that are specified by the corresponding treatment theory, and are hypothesized or known to be necessary for the treatment's effects on the treatment target.
      Inactive ingredients (of a treatment) – Attributes of a treatment that do not define or moderate the impact of the treatment on the target. Ingredients may be presumed to be inactive because they are not addressed by a treatment theory (eg, the building in which the treatment is conducted) or have been empirically determined to be inactive.
      Ingredients – See Treatment ingredients.
      Mechanism of action – Process by which the treatment's essential ingredients induce change in the target of treatment. A treatment theory should specify how the essential ingredients engage mechanisms of action to bring about desired treatment effects, that is, specification of the mechanism of action explains how the essential ingredients alter the treatment target within the framework of the treatment theory. Similarly, additional mechanisms of action specify how other active ingredients moderate the effects of the treatment.
      Nonvolitional treatments – Treatments whose hypothesized mechanisms of action require no effort on the part of the recipient (other than cooperation/nonresistance). Unlike volitional treatments (subsequently defined), the recipient of nonvolitional treatment is always the patient/client undergoing rehabilitation, not a third party (eg, caregiver).
      Patient/client – Person with a disability or at risk of a disability who is the intended beneficiary of treatment.
      Progression - Clinician's deliberate, systematic alteration of the treatment to maintain, over time, the degree of challenge to the body system/behavior(s) selected for change. Progression is often triggered by improvements in the target of treatment; therefore, the pace of progression (within a single treatment contact or a course of treatment) typically depends on the pace of change in the treatment target. The form that treatment progression takes (and hence the nature of the challenge that is being maintained) is often specified by the treatment theory; therefore, multiple treatment sessions may need to be observed to distinguish between one treatment and another.
      Recipient (of treatment) – Individual whose function/behavior is intended to be changed directly as a result of treatment. In most cases this is the person with a disability (patient/client recipient), but in some instances a caregiver or employer may be the other recipient who is changed by the intervention (eg, to provide care or intervention to the patient/client or to create a more supportive environment for the patient/client).
      Rehabilitation treatment taxonomy – System of classifying rehabilitation treatments based on a principle or set of principles that allows for distinctions between treatments, which have practical and/or theoretical utility.
      Session (of treatment) – Individual episode of treatment (typically minutes to a few hours), which may be repeated during a course of treatment.
      Target of treatment/treatment target – Aspect of the recipient's functioning, or personal factor, that is predicted to be directly changed by the treatment's mechanism of action. Specification of the target of treatment in a theory in terms of an International Classification of Functioning, Disability and Health variable(s) helps to define the scope of the treatment/treatment theory. (The aim of treatment refers to changes in functioning obtained in indirect ways—see Aim(s) (of treatment), above. Although there are instances where the target of treatment is functionally important in its own right, without reference to distal enablement effects, we nevertheless reserve the term treatment aim only for the functionally relevant clinical effects that are distal to the treatment target.)
      Taxonomy – System of classification or categorization based on characteristics that have important pragmatic or theoretical implications.
      Treatment – Action taken by a health professional, in the context of contact with a treatment recipient, to alter the functioning of an individual with a disability or at risk of a disability. Treatment is defined broadly to include provision of information, devices, and referrals, specific active experiences, and passive interventions.
      Treatment grouping – Broad class of treatments that is similar in essential ingredients (eg, forms of energy) and is able to act on a class of similar treatment targets (eg, tissue properties).
      Treatment ingredients – Observable (and, therefore, in principle, measurable) actions, chemicals, devices, or forms of energy that are selected or delivered by the clinician. See also Active ingredients, Dosing parameters, Essential ingredients, and Inactive ingredients.
      Treatment theory – Conceptual system that predicts the effects of specific forms of treatment on their targets, specifying the law(s) that expresses the relations between essential ingredients and treatment target changes. (This is similar to Mechanism of action but may be broader and more inclusive.)
      Volitional treatments – Treatments where a hypothesized mechanism(s) of action requires some effort on the part of the treatment recipient.

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