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Table 3 Methods for classifying/grouping outcomes (n = 17)

From: The COMET Handbook: version 1.0

Reference Method for classifying/grouping outcomes
Duncan (2000) [225] Each outcome measure was classified into one of the following categories: death or, at the level of pathophysiological parameters (blood pressure, laboratory values, and recanalisation), impairment, activity, or participation. Measures were classified according to the system used by Roberts and Counsell [226], which includes the Rankin/modified Rankin scale as a measure of activity rather than participation
Sinha (2012) [60] Each outcome was grouped into one of the following six outcome domains, some of which were further divided into subdomains: disease activity, physical consequence of disease, functional status, social outcomes and quality of life, side effects of therapy and health resource utilisation. Where it was unclear which domain was appropriate, this was resolved by discussion between the authors. Reference given in support of this approach: Sinha et al. 2008 [227]
Broder (2000) [129] List developed by staff at institution (but no further detail)
Distler (2008)[228] The results of this literature search were discussed at the first meeting of the Steering Committee. Based on this discussion, a list of 17 domains and 86 tools was set up for the first stage of the Delphi exercise to define outcome measures for a clinical trial in PAH-SSc. Domains were defined as a grouping of highly related features that describe an organ, disease, function, or physiology (e.g. cardiac function, pulmonary function, and quality of life)
Devane (2007) [173] Outcome measures addressing similar dimensions or events were discussed by the team and collapsed where possible. For example, various modes of delivery/birth were presented as ‘mode of birth (e.g. spontaneous vaginal, forceps, vaginal breech, caesarean section, vacuum extraction)’. This pilot tool was tested for clarity, with a sample of 12 participants, including 3 maternity care consumers, and subsequently refined
Smaïl-Faugeron (2013) [111] Because we expected a large diversity in reported outcomes, we grouped similar outcomes into overarching outcome categories by a small-group consensus process. The group of experts consisted of 6 dental surgeons specialising in paediatric dentistry, including 3 clinical research investigators. First, the group identified outcomes that were identical despite different terms used across trials. Second, different but close outcomes (i.e. outcomes that could be compared across studies or combined in a meta-analysis) were grouped together into outcome domains. Finally, the group, with consensus, determined several outcome categories and produced a reduced-outcome inventory
Merkies (2006) [229] In advance of the workshop, a list of outcome measures applied in treatment trials was prepared including their scientific soundness, WHO and quality of life classification (WHO classification reference is ICF)
Rahn (2011) [230] From this outcome inventory, the outcomes were organised and grouped into eight proposed overarching outcome domains: 1. Bleeding; 2. Quality of life; 3. Pain; 4. Sexual health; 5. Patient satisfaction; 6. Bulk-related complaints; 7. Need for subsequent surgical treatment and 8. Adverse events. Categories were determined based on their applicability to all potential interventions for abnormal uterine bleeding and the physician expert group’s consensus of their relevance for informing patient choices. Outcomes related to cost, resource use, or those determined by the review group to have limited relevance for assessing clinical effectiveness were excluded from categorisation and further analyses
Chow (2002) [231] Some detail but process not described – the endpoints employed in previous bone metastases trials of fractionation schedules were identified and listed in the first consensus survey under the following headings: 1. Pain assessments; 2. Analgesic assessments and primary endpoint; 3. Endpoint definitions; 4. Timing, frequency and duration of follow-up assessment; 5. When to determine a response; 6. Progression and duration of response; 7. Radiotherapy techniques; 8. Co-interventions following radiotherapy; 9. Re-irradiation. 10. Non-evaluable patients (lost follow-up) and statistics; 11. Other endpoints; 12. Other new issues and suggestions and 13. Patient selection issues
Van Der Heijde (1997) [232] Grouped into patient-assessed, physician-assessed or physician-ordered measures
Chiu (2014) [233] A wide variety of different outcomes measures were reported [in the studies included in the systematic review]. We classified these into 4 categories: postoperative alignment, sensory status, control measures and long-term change
Fong (2014) [139] Twenty-one maternal and 24 neonatal outcomes were identified by our systematic reviews, one randomised controlled trial and two surveys. The maternal components included complications associated with pre-eclampsia and were broadly classified under neurological, respiratory, haematological, cardiovascular, gastrointestinal, renal and other categories. The neonatal components were prematurity-associated complications involving respiratory, neurological, gastrointestinal, cardiovascular systems and management-based outcomes such as admission to the neonatal unit, inotropic support and use of assisted ventilation
Fraser (2013) [234] Based on an overall evaluation of intra-arterial head and neck chemotherapy, there are several outcome variables that should be monitored and reported when designing future trials. These outcome variables can be categorised into ‘Procedure-related’, ‘Disease control’ and ‘Survival’
Goldhahn (2014) [235] The group reached an agreement to use the ICF thereby identifying key domains within this framework using the nominal group technique. Recently, the WHO has established core sets for hand conditions [236]. A Comprehensive Core Set of 117 ICF categories were selected appropriate for conducting a comprehensive, multidisciplinary assessment. A brief core set of 23 ICF categories were selected, and considered more appropriate for individual health care professionals. The body functions contained in this core sets include emotional function, touch function sensory functions related to temperature and other stimuli, sensation of pain, mobility of joint functions, stability of joint functions, muscle power functions, control voluntary movement functions, and protective functions of the skin. The group agreed that the ICF categories would be consistent with clinicians’ current practice patterns of focussing on pain, joint range of motion and hand strength [237]
Saketkoo (2014) [238] The Delphi process began with an ‘item-collection’ stage called tier 0, wherein participants nominated an unrestricted number of potential domains (qualities to measure) perceived as relevant for inclusion in a hypothetical 1-year RCT. This exercise produced a list of >6700 items—reduced only for redundancy, organised into 23 domains and 616 instruments and supplemented by expert advisory teams of pathologists and radiologists
Smelt (2014) [159] We then grouped the answers [from round 1 of the Delphi questionnaires] according to the presence of strong similarity. During this process, we followed an inductive method, i.e. answers were examined and those considered to be more or less the same were grouped as one item. No fixed number of items was set beforehand in order to accommodate all new opinions. The answers were grouped by two of the authors (AS and VdG) separately, to ensure independence of assessments. Any discrepancies were resolved through a discussion with two other authors (ML and DK) who also checked whether they agreed with the items as formulated by AS and VdG
Wylde (2014) [137] The pain features that were retained after the three rounds of the Delphi study were reviewed and systematically categorised into core outcome domains by members of the research team [86]. The IMMPACT recommendations [239] were used as a broad framework for this process. Each individual feature was reviewed to determine whether it was appropriate to group it into an IMMPACT-recommended pain outcome (pain intensity, the use of rescue treatments, pain quality, temporal components of pain) or a new pain outcome domain. The developed outcomes domains were then reviewed to ensure that the features that they encompassed adequately reflected the domain and that the features were conceptually similar. These core outcome domains were subsequently discussed and refined by the Project Steering Committee and the PEP-R group
  1. ICF International classification of Functioning, Disability and Health, PAH-SSc pulmonary arterial hypertension associated with systemic sclerosis, PEP-R Patient Experience Partnership in Research (a patient and public involvement group specializing in musculoskeletal research), WHO World Health Organisation