Two recent papers published in Chiropractic & Manual Therapies by Murphy and Hurwitz[17, 18] highlight the sometimes confusing intersection between decision rules, patient classification and prediction of treatment outcome. The authors have previously published their work describing “diagnosis-based clinical decision rules” for patients with spinal pain.[19, 20] As mentioned, the classification of patients with spinal pain is an important and potentially promising area of research activity and this diagnosis-based strategy is a welcome addition to other classification approaches.[21–25]
However, the author’s use of the phrase “diagnosis-based clinical decision rule” is noteworthy as it represents a departure from convention. A review of the development of the “diagnosis-based clinical decision rule” reveals no formal derivation, validation or analysis of impact. Instead, the criteria for this rule were derived from non-systematic literature reviews.[19, 20] Therefore, the use of the phrase “diagnosis-based clinical decision rule” may be the cause of confusion as it implies the formal derivation and validation of a rule. Consequently, there is concern over the potential for a mistaken belief that the diagnosis-based decision rule represents a high level of evidence, while in its current form, it is an evidence-informed hypothesis. Therefore, it is not appropriate to refer to the criteria defining the diagnosis based classification approach as a clinical decision rule until the appropriately designed studies are undertaken.
In their recent publications, the authors have changed the terminology used to describe the diagnosis-based classification approach from “clinical decision rule” to “clinical decision guide.”[17, 18] While the former implies a strict methodology of derivation, validation, and impact analysis, the later is an informal term perhaps more appropriate for the current state of the diagnosis-based classification approach and yet it is possible that the significance of this terminology change may be missed by the casual observer.
Moreover, distinctions between “decision rule,” “prediction rule,” “decision guide,” and “prediction guide” can be subtle, and misunderstandings have potential to adversely impact clinical decision making. Although some may find such differences in terminology to be overly pedantic, these issues get to the heart of evidence appraisal and translation of evidence into practice and incorrectly identifying research findings as representing high level evidence (e.g., a fully developed CDR) has potential to mislead clinicians and adversely affect patient care.
This perspective leads to two fundamental questions with respect to the diagnosis based classification approach:
What level of evidence does the diagnosis-based approach represent?
How should this evidence be used to inform patient care?
In its current state, the diagnosis-based clinical decision guide is a theoretical approach for classifying patients with neck or back pain. The authors have identified the potential classification criteria based upon narrative literature reviews.[19, 20] While some of the individual studies identified in these reviews represent a high level of evidence, other studies underpinning the guide represent low level evidence. Furthermore, some aspects of the classification approach are hypothetical. The next logical step in the development of the diagnosis-based classification approach could be to undertake formal CDR derivation studies examining the multivariate relationships between potential predictor variables and treatment outcomes. Subsequently, the potential CDRs should be validated through the rigors of randomized trials. If broad validation of the CDRs were supported by experimental results, analyses of impact could then be undertaken. While it may be appropriate for CDR derivation study results to influence clinical decision making (e.g., when very little evidence is available in a particular area or on a localized level where the impact on patient care can be monitored), widespread implementation of a CDR requires validation. Consequently, given the hypothetical nature of the diagnosis-based clinical decision rule (now termed clinical decision guide), its widespread implementation by clinicians is premature.
Although in its current state the diagnosis-based clinical decision guide represents a preliminary and untested approach, new and innovative developments in neck and back pain classification such as this should be welcomed and their development encouraged. However, it is also important to understand the appropriate context for interpreting this classification approach and recognize its limitations. Despite its potential to inform future efforts of subgrouping patients with neck or back pain who may preferentially respond to one or more forms of therapy, the diagnosis-based classification approach is not ready for clinical implementation. Nevertheless, we are hopeful that future advancements in and additional knowledge of patient classification hold promise for improving the quality of healthcare provided to patients with spinal pain and the diagnosis-based clinical decision approach is no exception.