Clinical Research Network (CRN) update #13: choosing appropriate outcomes--considerations from PTClinResNet.

Ultimately, any health care intervention is intended to restore impaired body structures and functions, to overcome activity limitations and participation restrictions, and to prevent new symptoms and disabilities. The outcome of treatment is measured differently by the clinician and the patient. A clinician looks at outcomes relevant to the interventions through valid and reliable measurements. Patients are concerned with how well they feel and can participate in meaningful life activities. Increased recognition of the patient perspective and, more specifically, functioning and health has led to an increased effort in clinical research to develop concepts and instruments to measure "meaningful" outcomes. The recent Roadmap initiative of the National Institutes of Health (NIH)--Patient Reported Outcomes Measurement Information System (PROMIS, http://www. nihpromis.org/) (1)--is currently under development to specifically address this need.

In its original proposal, the PTClinResNet used the Nagi disablement model (2) as a framework for outcome analysis. However, the network has since adopted the International Classification of Functioning, Disability and Health (ICF) (3) in large part because of its acceptance by a broader community of health care professionals and its greater research potential. Using rules that specify links between items from specific instruments and corresponding ICF categories, (4) the representation of ICF domains of "body functions and structures" "activities," and "participation" as well as contextual factors can be investigated. The ICF is currently being applied in clinical research and practice in areas including rehabilitation medicine. (5)

The Table outlines the primary and secondary outcomes used for each of the 4 randomized clinical trims (RCTs) housed within PTClinResNet. With each RCT, there is at least one outcome specific to each of the major domains of the ICF framework ("body functions/structures" "activities" "participation"). Primary outcomes are those that are highly reliable, valid, and study specific (disability, population, specific aim). Furthermore, primary outcomes are the ones that were used for pre-proposal sample size estimates and accordingly are thought to be the outcomes that will be most directly influenced by the specific intervention.

Traditionally, each study included a set of secondary outcomes using study-specific measures at each major ICF level. Three studies used a common overall measure of health status (ie, SF-36), whereas the pediatrics RCT (PEDALS) used a similar but disability-specific health-related quality-of-life measure (ie, PedsQL).

References

(1) Patient Reported Outcomes Measurement Information System, PROMIS. http://www. nihpromis.org/.

(2) Nagi SZ. Disability concepts revisited: implications for prevention. In: Pope AM, Tarlov AR, eds. Disability in America: Toward a National Agenda for Prevention. Washington, DC: National Academy Press; 1991:309-327.

(3) World Health Organization. International Classification of Functioning, Disability and Health. Geneva: World Health Organization; 2001.

(4) Cieza A, Brockow T, Ewert T, et al. Linking health-status measurements to the International Classification of Functioning, Disability and Health. J Rehabil Med. 2002;34: 1-6.

(5) Stucki G, Ewert T, Cieza A. Value and application of the ICF in rehabilitation medicine. Disability and Rehabilitation. 2002;24: 932-938.

Table.
Primary and Secondary Outcomes and ICF Level for Each Study Housed in
PTCIinResNet (a)

RCT      Primary          ICF           Secondary        ICF
         Outcomes         Levels        Outcome          Levels

STEPS    Walking          Activities    Isometric        Body
         velocity-10 m                  joint torque;    Functions/
         (selected and                  Berg Balance     Structures
         fast);                         Scale; Fugl-
         endurance                      Meyer (lower
         (6-minute walk                 limb only)
         test)
                                        SF-36; SIS       Participation

MUSSEL   Oswestry         Body          SF-36            Participation
         Disability       Functions/
         Index            Structures;   5-minute walk    Activities
                          Activities    test

STOMPS   Wheelchair       Body          Joint torque     Body
         Users Shoulder   Functions/                     Functions/
         Pain Index       Structures                     Structures
                                        Wheelchair       Activities
                                        propulsion
                                        speed

                                        Physical         Activities
                                        activity level

                                        Community        Participation
                                        activity;
                                        SF-36

                                        Subjective       Participation
                                        quality of
                                        life

PEDALS   Joint torque     Body          PODCI; PedsQL    Body
                          Functions/                     Functions/
                          Structures                     Structures;
                                                         Participation;
                                                         Activities

(a) STEPS=Strength Training Effectiveness Post-Stroke, MUSSEL =
Muscle-Specific Strength Training Effectiveness Post-Lumbar
Microdisectomy, STOMPS = Strengthening and Optimal Movements for
Painful Shoulders in Chronic Spinal Cord Injury, PEDALS=Pediatric
Endurance and Limb Strengthening, SF-36=36-Item Short-Form Health
Survey, SIS=Sickness Impact Scale, PODCI=Pediatric Outcomes Data
Collection Instrument, PedsQL = Pediatric Quality of Life Inventory.