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ABSTRACT: BACKGROUND: The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) is a widely used patient reported outcome in osteoarthritis. An important, but frequently overlooked, aspect of validating health outcome measures is to establish if items exhibit differential item functioning (DIF). That is, if respondents have the same underlying level of an attribute, does the item give the same score in different subgroups or is it biased towards one subgroup or another. The aim of the study was to explore DIF in the Likert format WOMAC for the first time in a UK osteoarthritis population with respect to demographic, social, clinical and psychological factors. METHODS: The sample comprised a community sample of 763 people with osteoarthritis who participated in the Somerset and Avon Survey of Health. The WOMAC was explored for DIF by gender, age, social deprivation, social class, employment status, distress, body mass index and clinical factors. Ordinal regression models were used to identify DIF items. RESULTS: After adjusting for age, two items were identified for the physical functioning subscale as having DIF with age identified as the DIF factor for 2 items, gender for 1 item and body mass index for 1 item. For the WOMAC pain subscale, for people with hip osteoarthritis one item was identified with age-related DIF. The impact of the DIF items rarely had a significant effect on the conclusions of group comparisons. CONCLUSIONS: Overall, the WOMAC performed well with only a small number of DIF items identified. However, as DIF items were identified in for the WOMAC physical functioning subscale it would be advisable to analyse data taking into account the possible impact of the DIF items when weight, gender or especially age effects, are the focus of interest in UK-based osteoarthritis studies. Similarly for the WOMAC pain subscale in people with hip osteoarthritis it would be worthwhile to analyse data taking into account the possible impact of the DIF item when age comparisons are of primary interest.
BMC Musculoskeletal Disorders 12/2012; 13(1):265. · 1.58 Impact Factor
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ABSTRACT: Purpose: This study examined whether the mental representations of people with osteoarthritis (OA) were consistent with the International Classification of Functioning Disability and Health (ICF) model. Methods: A geographical cohort of 202 people with OA about to have joint replacement surgery completed postal questionnaires. Mental representations were measured by asking participants what they were hoping for from their joint replacement. Two expert judges classified these illness representations to the main ICF constructs of Impairment (I), Activity Limitation (A) and Participation Restriction (P). Results: There was strong agreement between the expert judges. There were a similar number of illness representations for each of the ICF constructs. The primary biomedical route of the ICF model was suggested by the ordering of the participants' illness representations i.e. I to A to P. Conclusions: The mental representations of people with OA were consistent with the ICF theoretical framework with all three ICF constructs of importance. It appeared that people with OA implicitly apply a biomedical causal model of disability, suggesting that treatments and interventions aimed at reducing impairment may only affect P indirectly, through A. Additionally, the methods provide a novel way of exploring the potential causal relationships between constructs of the ICF model. [Box: see text].
Disability and Rehabilitation 11/2012; · 1.50 Impact Factor
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ABSTRACT: Although disability can readily be conceived within a biomedical model as a product of disease, it can also be characterized as limitations in behaviour. Seen as a biomedical entity, psychologists' inputs focus on the emotional consequences of disability and on facilitating coping with the condition. By contrast, when disability is seen as behavioural, psychology's capacity to describe, measure, explain, and intervene to change behaviour become more pertinent. Disability is therefore a challenging topic for psychology and many branches have important things to contribute to our understanding of this subject. Whereas educational, occupational, clinical, and social psychology deal mainly with the context and consequences of disability, the focus in health psychology is on disability per se. The aim of this chapter is to describe models of disability currently used in health psychology, to consider how the models are used, and to reflect on the issues raised. Two main types of model are discussed--models that reflect the definition and measurement of disability, and models that address explanation and intervention. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
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ABSTRACT: Disability from chronic illness is a major problem for society, yet the study of its determinants lacks an overall theoretical paradigm. Johnston (1996) has proposed conceptualizing disability as behavior and integrating biomedical and behavioral predictors. Dixon, Johnston, Rowley, and Pollard (2008) tested a model including constructs from the International Classification of Functioning, Disability and Health (ICF) and the theory of planned behavior (TPB) using structural equation modeling; it fitted better and explained more variance than the ICF or TPB alone. We replicated their study with a new sample from the same population (orthopedic patients awaiting joint replacement) and also tested the model after the patients had surgery.
Two weeks before surgery, 342 orthopedic patients who had joint pain (most with arthritis) completed a questionnaire, with 228 completing it again 1 year after surgery. The authors tested Dixon et al.'s best-fit models cross-sectionally (before and after surgery) and assessed the goodness of fit of these imposed models to our data using structural equation modeling.
Findings strongly supported those of Dixon et al. Before surgery, results were very similar to Dixon et al. with all models accounting for significant variance and fitting well, but the integrated model fitted better and accounted for more variance. One year after surgery, Dixon et al.'s models showed even stronger fit to the data.
Although behavioral and biomedical (ICF) models were supported, the integrated model provided a better explanation of disability in this population than either of these models alone and suggests biopsychosocial interventions to reduce disability.
Rehabilitation Psychology 05/2012; 57(2):167-77. · 1.91 Impact Factor
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ABSTRACT: The International Classification of Functioning, Disability and Health (ICF) proposes three main constructs, impairment (I), activity limitation (A) and participation restriction (P). The ICF model allows for all paths between the constructs to be explored, with significant paths likely to vary for different conditions. The relationships between I, A and P have been explored in some conditions but not previously in people with osteoarthritis prior to joint replacement. The aim of this paper is to examine these relationships using separate measures of each construct and structural equation modelling.
A geographical cohort of 413 patients with osteoarthritis about to undergo hip and knee joint replacement completed the Aberdeen measures of Impairment, Activity Limitation and Participation Restriction (Ab-IAP). Confirmatory factor analysis was used to test the three factor (I, A, P) measurement model. Structural equation modelling was used to explore the I, A and P pathways in the ICF model.
There was support from confirmatory factor analysis for the three factor I, A, P measurement model. The structural equation model had good fit [S-B Chi-square = 439.45, df = 149, CFI robust = 0.91, RMSEA robust = 0.07] and indicated significant pathways between I and A (standardised coefficient = 0.76 p < 0.0001) and between A and P (standardised coefficient = 0.75 p < 0.0001). However, the path between I and P was not significant (standardised coefficient = 0.01).
The significant pathways suggest that treatments and interventions aimed at reducing impairment, such as joint replacement, may only affect P indirectly, through A, however, longitudinal data would be needed to establish this.
BMC Musculoskeletal Disorders 05/2011; 12:97. · 1.58 Impact Factor
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ABSTRACT: Background. Previous research has demonstrated that control cognitions predict functional limitations following stroke. This paper reports a preliminary evaluation of the effects of a workbook intervention, designed to enhance perceptions of control, in reducing disability in patients discharged from hospital following stroke. Methods. Thirty-nine patients living at home who had had a stroke within the 2 previous years completed baseline assessments of functional limitations, mood and perceived control. They were then randomly allocated to either a Workbook Intervention or a Wait control group and functional limitation and mood outcomes were assessed 1 month later. Results. Results showed no benefit of the intervention, but both groups showed reduced functional limitations. Reductions in functional limitations were correlated with increases in perceptions of control. Conclusions. Clearly, the workbook intervention needs to be strengthened before a full evaluation would be worthwhile for this clinical group. It is possible that both groups demonstrated spontaneous recovery or may have benefited from the additional attention given by the researcher. These benefits were associated with enhanced perceptions of control, contributing to previous findings suggesting that control cognitions may be both a consequence and a determinant of functional limitations.
British Journal of Health Psychology 12/2010; 5(4):413 - 420. · 2.70 Impact Factor
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ABSTRACT: The factors that affect referral for total joint arthroplasty (TJA) have been widely studied. Implicit in this work is the assumption that patient health status should determine priority for surgery. However, specification of patient health status lacks a strong theoretical framework. This study employs the WHO model of health outcomes, the International Classification of Functioning, Disability and Health (ICF), to examine patient health factors in the referral process for TJA.
Within 8 weeks prior to TJA, 260 patients electing for primary TJA completed a questionnaire which measured the ICF (impairment, activity limitations and participation restrictions) and four types of delay in their journey from initial consultation with their primary care physician to surgery.
Impairment did not affect any stage of the referral process. In contrast, patients who had experienced a delay of 26 weeks or less between referral to a surgeon and being placed on the waiting list for surgery reported greater activity limitations and participation restrictions than patients who had waited more than 26 weeks. Further, patients who reported having wanted surgery for more than 52 weeks reported greater participation restrictions than patients who had wanted surgery for less than 52 weeks.
The ICF identifies three health outcomes, two of which (activity limitations and participation restrictions) are related to delay in the referral process for TJA. The ICF is a useful theoretical framework for the study of factors that influence prioritisation for surgery. The level of functional and social disability appears to inform prioritisation for TJA by consultant orthopaedic surgeons.
Quality and Safety in Health Care 12/2010; 19(6):e23. · 1.68 Impact Factor
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ABSTRACT: To test the hypothesis that interventions targeting the relief of pain and disability in musculoskeletal diseases may have differential effects on activity limitation and participation restriction as defined in the International Classification of Functioning, Disability and Health (ICF).
Full data were obtained for 3 randomized controlled trials that used the Western Ontario and McMaster Universities Osteoarthritis Measure (WOMAC), the Medical Outcomes Study Short-form 36 (SF-36), or the Oswestry Disability Questionnaire as their primary outcome measures. The trial outcomes were reanalyzed using items previously designated as assessing pure activity limitation (A) or participation restriction (P), or a mixture of the 2 (A/P) only, and the results compared with the outcomes found using the full scales, which assess a mixture of outcome domains.
The results did not refute the hypothesis. An exercise-based intervention and injection therapies both appeared to have more effect on participation restriction (P) than on activity limitation (A), while a drug-based intervention had more effect on A than on P.
Different interventions used to treat musculoskeletal disorders may have differential effects on impairment, activity limitation, and restricted participation. The use of outcome measures that do not differentiate these 3 domains may obscure the true value of an intervention.
The Journal of Rheumatology 09/2010; 37(9):1923-31. · 3.69 Impact Factor
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ABSTRACT: The purpose of the study was to evaluate the validity of the self-administered Aberdeen Measures of Impairment, Activity Limitation and Participation Restriction (Ab-IAP): by investigating how participants interpret and respond to questions using the cognitive interviewing technique.
Twenty patients with osteoarthritis of the knee or hip participated in a cognitive interview whilst completing the Ab-IAP. Interviews were conducted using the concurrent 'think aloud' design. All interviews were audio recorded and transcribed verbatim and analysed (i) using a standardised classification scheme to identify four types of response problems and (ii) thematically using the constant comparative technique.
Participants used various response strategies when answering questions about impairment, activity limitations and participation restriction. Problems were judged to be present in 3.1% of participants' responses for the item Ab-IAP. Thematic analysis provided insight into the type and nature of problems people experienced when completing the Ab-IAP measures. The problems identified were mainly comprehension and response problems.
Participants had minimal difficulties completing the Ab-IAP; however those difficulties identified have prompted suggestions for improving the measures. The cognitive interviews produced results that were compatible with statistical analysis of the measures.. Cognitive interviewing was beneficial for testing the validity and acceptability of new Ab-IAP measures. The results demonstrates that the Ab-IAP, in addition to being theoretically-based and having good psychometric properties, elicits appropriate responses.
BMC Musculoskeletal Disorders 01/2010; 11:182. · 1.58 Impact Factor
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ABSTRACT: The International Classification of Functioning, Disability and Health (ICF) proposes three main health outcomes, Impairment (I), Activity Limitation (A) and Participation Restriction (P), but good measures of these constructs are needed The aim of this study was to use both Classical Test Theory (CTT) and Item Response Theory (IRT) methods to carry out an item analysis to improve measurement of these three components in patients having joint replacement surgery mainly for osteoarthritis (OA).
A geographical cohort of patients about to undergo lower limb joint replacement was invited to participate. Five hundred and twenty four patients completed ICF items that had been previously identified as measuring only a single ICF construct in patients with osteoarthritis. There were 13 I, 26 A and 20 P items. The SF-36 was used to explore the construct validity of the resultant I, A and P measures. The CTT and IRT analyses were run separately to identify items for inclusion or exclusion in the measurement of each construct. The results from both analyses were compared and contrasted.
Overall, the item analysis resulted in the removal of 4 I items, 9 A items and 11 P items. CTT and IRT identified the same 14 items for removal, with CTT additionally excluding 3 items, and IRT a further 7 items. In a preliminary exploration of reliability and validity, the new measures appeared acceptable.
New measures were developed that reflect the ICF components of Impairment, Activity Limitation and Participation Restriction for patients with advanced arthritis. The resulting Aberdeen IAP measures (Ab-IAP) comprising I (Ab-I, 9 items), A (Ab-A, 17 items), and P (Ab-P, 9 items) met the criteria of conventional psychometric (CTT) analyses and the additional criteria (information and discrimination) of IRT. The use of both methods was more informative than the use of only one of these methods. Thus combining CTT and IRT appears to be a valuable tool in the development of measures.
Health and Quality of Life Outcomes 06/2009; 7:41. · 2.11 Impact Factor
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ABSTRACT: Between-participant research has shown that high negative affectivity predicts greater activity limitations and vice versa. This study examined both between- and within-participant associations of negative and positive affectivity with activity levels using ecological momentary assessment.
Participants were 25 people who had undergone joint replacement surgery 12 months previously. Participants made multiple reports of their activity and positive and negative affectivity over a single day using a computerized diary. Activity was also objectively recorded using an activity monitor. The following day, participants made a self-report of their activity over the measurement day and general positive and negative affectivity levels were recorded.
Higher self-reported walking time over the whole measurement day was associated with higher general positive affectivity but not negative affectivity. However, using ecological momentary assessment, higher diary reports of negative affectivity predicted increased activity levels while positive affectivity neither predicted nor was predicted by activity.
These findings demonstrate the importance of within-participant methodology in detecting subtle and immediate effects of individuals' mood on behavior that may differ from findings investigating between-participant effects over longer time periods.
Rehabilitation Psychology 03/2009; 54(1):83-90. · 1.91 Impact Factor
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ABSTRACT: Modern joint replacements have been available for 45 years, but we still do not have clear indications for these interventions, and we do not know how to optimize the outcome for patients who agree to have them done. The MOBILE programme has been investigating these issues in relation to primary total hip and knee joint replacements, using mixed methods research. There have been five main strands: (1) Epidemiological investigations to find out who is receiving total hip and knee replacements in the National Health Service (NHS). This has shown that there are extensive variations in different regions of the UK, with inequalities and probable inequities in the provision of these operations; (2) Epidemiological work to ascertain the population-based needs for the operations, showing under-provision of knee joint replacements, and a relative reluctance of both patients and GPs to consider knee surgery; (3) Quantitative and qualitative research into the views of patients, health care professionals and the public on the indications for, and prioritization of, total hip and knee joint replacements. This has shown lack of agreement within or between professional groups, as well as a mismatch between the views of patients and the public, and those of professionals; (4) Theoretical and experimental work on patient-related outcome measures, and the development of new instruments to assess both pain and function in people with osteoarthritis, based on the International Classification of Function, as well as a new integrated model of function; (5) Cohort studies of patients undergoing hip or knee joint replacements to find out what the determinants of good and bad outcomes are. These studies have emphasized the huge variation in disease severity at the time of surgery. The challenge now is to use and implement our findings for maximum patient benefit.
Journal of Health Services Research & Policy 10/2008; 13 Suppl 3:47-56. · 1.73 Impact Factor
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ABSTRACT: This study examined whether spousal confidence in care-recipient recovery can predict recovery from activity limitations following stroke and how spousal confidence relates to stroke survivor self-efficacy for recovery.
A prospective design was used. Measures were gathered from stroke survivor/spouse dyads at two time points, both postdischarge from the hospital following stroke (N=109).
The dependent variable was recovery from ambulatory activity limitations over 6 weeks, as measured by the Functional Limitations Profile. A single spousal confidence item was tailored to an ambulatory behavior that the stroke survivors could not perform at Time 1.
Spousal confidence was correlated with ambulation recovery (r=-0.23, p<.05) and stroke survivor self-efficacy for recovery (r=.25, p<.05). Higher spousal confidence was associated with a better recovery and greater stroke survivor self-efficacy for recovery, but not with initial health status or practical support received.
The relationship between caregiver confidence, care-recipient self-efficacy for recovery, and recovery outcomes needs further elucidation.
Health Psychology 04/2008; 27(2):286-90. · 3.87 Impact Factor
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ABSTRACT: This study explored the ability of the Chronic Pain Grade Questionnaire (CPG) to operationalise the WHO's model of health outcomes, namely the International Classification of Functioning, Disability and Health (ICF). Twelve expert judges used the method of discriminant content validation to allocate the seven items of the CPG to one or more ICF outcome, namely, impairment, activity limitations and participation restrictions. One-sample t-tests classified each item as measuring impairment, activity limitations or participation restrictions, or a combination thereof. The results indicated that the CPG contains items able to measure each of the three ICF outcomes. However, the pain grade classification system used in the CPG conflates the ICF outcomes. The implication of this conflation of outcome for the assessment of interventions is discussed.
Pain 09/2007; 130(3):249-53. · 5.78 Impact Factor
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ABSTRACT: Disability following stroke is highly prevalent and is predicted by psychological variables such as control cognitions and emotions, in addition to clinical variables. This study evaluated the effectiveness of a workbook-based intervention, designed to change cognitions about control, in improving outcomes for patients and their carers.
At discharge, stroke patients were randomly allocated (with their carers) to a 5-week intervention (n = 103) or control (normal care: n = 100). The main outcome (at 6 months) was recovery from disability using a performance measure, with distress and satisfaction as additional outcomes.
The intervention group showed significantly better disability recovery, allowing for initial levels of disability, than those in the control group, F(1,201) = 5.61, p = 0.019. Groups did not differ in distress or satisfaction with care for patients or carers. The only psychological process variable improved by the intervention was Confidence in Recovery but this did not mediate the effects on recovery.
A large proportion of intervention participants did not complete the workbook tasks. This was perhaps associated with the fairly low level of personal contact with workbook providers. The modest success of this intervention suggests that it may be possible to develop effective behavioural interventions to enhance recovery from disability in stroke patients.
Disability and Rehabilitation 08/2007; 29(14):1117-27. · 1.50 Impact Factor
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ABSTRACT: Subjective measures involving clinician ratings or patient self-assessments have become recognised as an important tool for the assessment of health outcome. The value of a health outcome measure is usually assessed by a psychometric evaluation of its reliability, validity and responsiveness. However, psychometric testing involves an accumulation of evidence and has recognised limitations. It has been suggested that an evaluation of how well a measure has been developed would be a useful additional criteria in assessing the value of a measure. This paper explored the theoretical background and methodological development of subjective health status measures commonly used in osteoarthritis research. Fourteen subjective health outcome measures commonly used in osteoarthritis research were examined. Each measure was explored on the basis of their i) theoretical framework (was there a definition of what was being assessed and was it part of a theoretical model?) and ii) methodological development (what was the scaling strategy, how were the items generated and reduced, what was the response format and what was the scoring method?). Only the AIMS, SF-36 and WHOQOL defined what they were assessing (i.e. the construct of interest) and no measure assessed was part of a theoretical model. None of the clinician report measures appeared to have implemented a scaling procedure or described the rationale for the items selected or scoring system. Of the patient self-report measures, the AIMS, MPQ, OXFORD, SF-36, WHOQOL and WOMAC appeared to follow a standard psychometric scaling method. The DRP and EuroQol used alternative scaling methods. The review highlighted the general lack of theoretical framework for both clinician report and patient self-report measures. This review also drew attention to the wide variation in the methodological development of commonly used measures in OA. While, in general the patient self-report measures had good methodological development, the clinician report measures appeared less well developed. It would be of value if new measures defined the construct of interest and, that the construct, be part of theoretical model. By ensuring measures are both theoretically and empirically valid then improvements in subjective health outcome measures should be possible.
Health and Quality of Life Outcomes 02/2007; 5:14. · 2.11 Impact Factor
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ABSTRACT: Disability (activity limitation) is an important and common health outcome for patients with osteoarthritis, making accurate measures essential. This paper explores self-report measures of activity limitation associated with osteoarthritis and reports on recent conceptual advances that impact on the measurement of activity limitation.
The Western Ontario and McMaster Universities Osteoarthritis Index and the Short Form-36, the most commonly used measures to assess activity limitation, continue to be validated in osteoarthritis. There has been little consensus, however, about which measure to use across different types of osteoarthritis. While new measures have been developed to assess activity limitation, it remains unclear whether or not these are an improvement over existing measures. The International Classification of Functioning, Disability and Health is becoming an important consideration. Commonly used measures do not map directly onto individual constructs of this classification, however a new measure for Japanese people with knee osteoarthritis was developed based on these constructs.
There have been significant developments in the conceptual approach to measuring activity limitation. Measures are needed that operationalize activity limitation as defined by the International Classification of Functioning, Disability and Health (within or ideally across cultures), providing a common underlying construct for measures and hence facilitating comparability across studies.
Current Opinion in Rheumatology 10/2006; 18(5):531-6. · 4.31 Impact Factor
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ABSTRACT: To explore whether commonly used osteoarthritis (OA) health outcome instruments (and items) are measuring single or multiple health outcomes using the International Classification of Functioning, Disability and Health (ICF) definitions.
Ten expert judges allocated 342 items from 13 instruments to one or more ICF construct, i.e., Impairment (I), Activity Limitation (A), and Participation Restriction (P). One-sample t tests were used to classify each item as measuring uniquely I, A, or P or some combination (i.e., IA, IP, AP, or IAP).
Overall, 12 of the 13 instruments had items that measured a combination of outcome domains (i.e., IA, IP, AP, or IAP). Only the American Knee Society Score (AKS) had all items uniquely measuring either I or A. The instrument with the best representation of items for Impairment was the AKS, for Activity Limitation the WOMAC and Lequesne knee index, and for Participation Restriction the Disease Repercussion Profile.
All the existing OA outcome instruments, except one, had some items that were assessing more than one health outcome. Use of these instruments may either mask true treatment effects or make an effect difficult to attribute if the content is unclear. We determined which instruments were the best for measuring each health outcome. To improve the assessment of health outcomes in OA, new instruments that uniquely measure the 3 ICF constructs should be developed and all 3 should be included in relevant studies.
The Journal of Rheumatology 05/2006; 33(4):757-63. · 3.69 Impact Factor
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ABSTRACT: Our earlier work had established that moderate depression significantly decreased over the first 6 months after stroke, whereas anxiety levels remained moderate but stable. This study examines the factors predictive of anxiety and depression to 3 years.
Patients were assessed on six occasions: on hospital admission, 10-20 days following admission, 1 and 6 months following discharge, and 1 and 3 years poststroke, with 38 of the original sample of 101 taking part at Year 3. Demographic and clinical variables, disability, handicap, and psychological measures were used to predict 3-year anxiety and depression, controlling for earlier levels of anxiety or depression.
Multiple regression analyses of anxiety at 3 years, controlling for gender and previous anxiety, demonstrated that neither of the significant partial correlates of 6-month depression or satisfaction with treatment persisted. Gender effects persisted when controlling for previous anxiety. Multiple regression analyses of depression at 3 years, controlling for early depression, found that exercise, treatment satisfaction, anxiety, and handicap added significantly to the prediction of lower depression.
Anxiety remains stable over 3 years poststroke and is best explained by prior, early, anxiety, and female gender. Depression reduces over time and was explained by modifiable cognitions and behaviours, which replicates previous findings.
Journal of Psychosomatic Research 11/2005; 59(4):209-13. · 3.30 Impact Factor
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ABSTRACT: Karasek's demand-control model of job strain was used in an attempt to extend previous work examining the psychological impact of informal caregiving in stroke.
Data were gathered from 138 informal caregivers/patient dyads at two time points. The dependent variables were the caregiver's anxiety and depression [Hospital Anxiety and Depression Scale (HADS)]. The predictor variables were caregiver demand (stroke survivor's assessment of their physical and psychosocial functional limitations) and control (caregiver's perceived control over stroke survivor's recovery).
In a cross-sectional analysis of Times 1 and 2 data, main effects for demand and/or control were detected for anxiety and depression. Contrary to prediction, in longitudinal analysis of change, it was found that decreasing control, along with increasing demand, was associated with reduced distress.
The model was moderately successful in predicting emotional distress. The relative importance of caregiver demand and control in predicting outcomes changed over time in these data. Attempts to replicate these findings are recommended.
Journal of Psychosomatic Research 04/2005; 58(3):243-51. · 3.30 Impact Factor
