Author Response

We very much appreciate the commentary made by Jette¹ on our articles.^2,3 We see this exchange as part of an ongoing dialogue and debate regarding the use of the International Classification of Functioning, Disability and Health (ICF)⁴ by physical therapists.

The World Health Organization (WHO) had a clear aim when it developed the ICF, and that is “to provide a unified and standard language and framework for the description of health and health-related states.”⁴ Specifically, this framework and language was meant to “code” the functioning of an individual and serve as a communication tool between and among health disciplines. The WHO also was clear that the ICF aims to serve as a scientific basis for the understanding of health and disability outcomes and determinants.^4(pp3–5) These WHO guiding principles were the driving force behind our articles.

In his commentary, Jette was explicit about the benefits of using the ICF, with prudent consideration of the aims above. He has made mention that the ICF as a conceptual framework and as a classification system is essential to and can positively affect physical therapist practice. At the same time, Jette pointed out the utility and methodological challenges that we face in using the ICF codes and its qualifiers. We recognize and agree with Jette that these limitations must be carefully examined with robust thinking and, most importantly, with sound science.

Fundamentally, the ICF provides clinicians with “what” to measure (in a patient encounter) and a first practical approach about “how” to measure based on the ICF qualifiers. To answer the question of “how” to measure, new scientific-based proposals have to be worked out in the near future. Users of the ICF are challenged to answer the question of “how” to measure when implementing this classification in clinical practice and research.

However, the question of “what” to measure has to be answered first because it is fundamental to clinical practice. The ICF Core Sets, as a list of categories, provide the “what” to measure for a specific health condition or event. The combined use of an ICF Core Set and the ICF qualifier results in a “profile” of the patient. At this point, the question of how to arrive at a qualifier rating is up to the users and is not the question that was intended to be fully answered in our articles. Our primary intention was to comprehensively address the potential benefits of the Core Sets to efficiently identify what to measure. The use of the ICF Core Sets could alert the clinician to assess aspects of the patient's daily life (eg, activities and participation) that otherwise would not have been documented without the categories provided by the Core Set.⁵ By providing the functioning profile of the patient, a comprehensive picture of the “lived experience” of the patient, including the magnitude of the problem in each functioning aspect, is captured and, thus, could be appropriately addressed in the intervention.

The ICF Core Sets represent the domains that are relevant to a specific condition or event because, as Jette notes, the ICF Core Sets are based on evidence from the literature and with extensive input from the clinical and patient's perspectives. Therefore, this gives the Core Sets, at the very least, face and content validity, which can both lend to the property of sensibility.⁶

The ICF handbook is explicit that an ICF category as a code is most useful when a qualifier also is used (ie, 0–4 level of impairment).^4(p21) Unfortunately, the qualifier in the ICF has limitations, which Jette eloquently addressed, and this is where concerns about psychometric quality become pronounced. Interrater reliability is an ongoing issue with the ICF qualifiers, with agreement of only up to moderate at best.^7–10 Therefore, we agree with Jette that there is a strong need to improve the operational definition of the ICF category and to closely examine the measurement properties.

More can be done to improve the definitions of ICF categories, such as combining category descriptions from the ICF handbook⁴ and developing a more specific instruction to better operationalize each category.¹¹ This was the approach used in the most recent manual of the American Psychological Association.¹²

To measure an ICF category, 2 approaches have been proposed: (1) the ICF qualifiers, as indicated in our articles, can be used, or (2) when possible, scores or ratings from standard clinical tests or patient-reported instruments (eg, 100-mm visual analog scale for pain) can be used.¹¹ If there are no validated instruments available for that ICF category, an ICF category interval scale can be created based on parts of a clinical test or some items of a questionnaire using advanced methods such as Rasch analysis.^11,13 Specifically, items can be selected from validated measures that are linked to an ICF category, and an interval scale can be created as a way of operationalizing that ICF category.¹³ To measure across different ICF categories, condition-specific patient-reported measures that are Core Set based can be used. Categories from an ICF Core Set also can serve as a basis for creating an aggregate scale.¹⁴ Work by Cieza and colleagues¹⁵ illustrates how a clinical measure based on the categories from ICF Core Set for osteoarthritis can be developed. The ICF provides a comprehensive list of domains from which clinicians can draw during patient assessment. For researchers, the ICF as a whole can be a “database” of domains that one can use to develop or integrate into instruments or measures.¹⁶

We agree with Jette that psychometrically sound instruments are needed to measure the various categories identified in ICF Core Sets, in particular, and in ICF, generally. This research effort should be given high priority, in our opinion. We also believe that there is value in using ICF-based Core Sets to identify the “what” to measure when examining patients. By using Core Sets, clinicians will be more likely to address the domains of health that are important in patients' lives. We see no reason to forestall use of the ICF in daily practice until psychometrically sound instruments for all ICF categories are developed. Integrating currently available instruments with ICF categories and Core Sets will, in our opinion, advance practice.

• © 2010 American Physical Therapy Association