The Association of Health Locus of Control with Clinical and Psychosocial Aspects of Living with Multiple Sclerosis.

Health Locus of control (LOC) refers to one's beliefs regarding control over one's health. This study aimed to determine the relationship between LOC on clinical and psychosocial aspects associated with multiple sclerosis (MS). 5059 participants with MS completed a questionnaire pack including the Multidimensional Health Locus of Control Scale. Associations between LOC and sociodemographic (age, gender, educational level) and clinical variables (duration, disability, depression, anxiety, self-efficacy, QoL) were explored. LOC was found to be significantly associated with all of the clinical variables and age, but not gender or educational level. When controlling for level of disability, Chance (CLOC) was associated with higher self-efficacy, lower anxiety and higher QoL than Powerful Others (PLOC), while Internal (ILOC) had no association. The proportion with ILOC preference was lower in increased disability. In MS, believing that health is controlled mainly by chance confers the most benefit with regard to quality of life. There is prima-facie evidence that LOC preference changes with MS progression, in a pattern that is protective against psychological distress.

Validation and assessment of minimally clinically important difference of the unadjusted Health Assessment Questionnaire in a Danish cohort: uncovering ordinal bias.

Objectives: The Stanford Health Assessment Questionnaire Disability Index (HAQ-DI) is a widely used patient-reported outcome for functional disability in rheumatoid arthritis (RA). Minimal clinically important differences (MCIDs) in the HAQ-DI were previously calculated based on device-corrected ordinal HAQ-DI scores, leading to limited generalizability and validity for today's patients. Our objectives were to examine the internal construct validity of the unadjusted HAQ-DI and to determine an MCID in a cohort of Danish RA patients based on the transformed linear logit scale of the HAQ-DI.Method: The study included 362 RA patients registered in the DANBIO registry. The Rasch model was fitted to HAQ-DI data at baseline and after 3 months' follow-up. MCID was calculated as the median changes in the original HAQ-DI score and logit HAQ-DI score in those patients who had experienced minimal improvement (15-30 mm on a 0-100 mm Patient Global scale).Results: HAQ-DI data showed acceptable fit to the Rasch model at both time-points, and consistent item ranking across time indicated instrument invariance. Sixty-one patients (16.8%, ~1/6) had an improvement above the MCID on the logit scale but improvement below the MCID on the original scale, while the opposite was not the case for any patients.Conclusions: The Danish unadjusted version of the HAQ-DI showed acceptable internal construct validity. Application of the logit MCID classified an additional one in six patients as having achieved an MCID compared to the MCID calculated on the ordinal scale, which may have potential implications for the powering of future studies.

The WHOQOL-BREF: a modern psychometric evaluation of its internal construct validity in people with multiple sclerosis.

PURPOSE: Symptoms of Multiple Sclerosis (MS) differentially impact upon quality of life (QoL) and a comprehensive measure is required for use in observational and interventional studies. This study examines the abbreviated World Health Organisation Quality of Life tool (WHOQOL-BREF) which was designed to be used as a broad measure of QoL across different cultures and diseases. METHODS: Data were collected from 3186 subjects as part of the TONiC study in MS and was examined with a systematic, iterative approach using Rasch analysis to investigate the internal construct validity of the WHOQOL-BREF. RESULTS: Mean age was 49.8 years (SD 11.8), disease duration was 11.2 years (SD 9.6) and 73.2% were female. Subjects represented all stages of MS with EDSS scores of 0-4, 4.5-6.5, 7-7.5 and ≥ 8 seen in 49.8%, 38.5%, 6.8% and 4.9% of patients, respectively. Using a super-item approach, it was possible to demonstrate fit to the assumptions of the Rasch model for 3 of the 4 domains of the WHOQOL-BREF (physical, psychological and environment) as well as a broad 24-item total score. In addition, item subsets derived from the stem of each question were shown to function as novel scales measuring impact and life satisfaction. We have provided transformation tables from ordinal raw scores to interval scales where data are complete. CONCLUSIONS: The validation of multiple conceptual frameworks validates the WHOQOL-BREF as a powerful and flexible end-point for use in clinical trials and in testing conceptual models of factors influencing QoL in MS.

The Valued Life Activities Scale (VLAs): linguistic validation, cultural adaptation and psychometric testing in people with rheumatic and musculoskeletal diseases in the UK.

BACKGROUND: The Valued Life Activities Scale (VLAs) measures difficulty in daily activities and social participation. With various versions involving a different number of items, we have linguistically and culturally adopted the full VLAs (33-items) and psychometrically tested it in adults with rheumatic and musculoskeletal diseases in the United Kingdom. METHODS: Participants with Rheumatoid Arthritis, Ankylosing Spondylitis, Chronic Pain/ Fibromyalgia, Chronic Hand/ Upper Limb Conditions, Osteoarthritis, Systemic Lupus, Systemic Sclerosis and Primary Sjogren's Syndrome were recruited from out-patient clinics in National Health Service Hospitals, General Practice and patient organisations in the UK. Phase1 involved linguistic and cultural adaptation: forward translation to British English; synthesis; expert panel review and cognitive debriefing interviews. In Phase2 participants completed postal questionnaires to assess internal construct validity using (i) Confirmatory Factor Analysis (CFA) (ii) Mokken scaling and (iii) Rasch model. RESULTS: Responders (n = 1544) had mean age of 59 years (SD13.3) and 77.2% women. A CFA failed to support a total score from the 33-items (Chi Square 3552:df 464: p < 0.0001). Mokken scaling indicated a strong non-parametric association between items. Fit to the Rasch model indicated that the VLAs was characterised by multidimensionality and item misfit, which may have been influenced by clusters of residual item correlations. An item banking approach resolved a 25-item calibrated set whose application could accommodate the 'does not apply to me' response option. CONCLUSIONS: The UK version of the VLAs failed to satisfy classical and modern psychometric standards for complete item sets. However, as the scale is not usually applied in complete format, an item bank approach calibrated 25 items with fit to the Rasch model. Suitable Computer Adaptive Testing (CAT) software could implement the item set, giving patients the choice of whether an item applies to them, or not.

Revisiting the disabilities of the arm, shoulder and hand (DASH) and QuickDASH in rheumatoid arthritis.

BACKGROUND: Limitations in upper limb functioning are common in Musculoskeletal disorders and the Disabilities of the Arm, Shoulder and Hand scale (DASH) has gained widespread use in this context. However, various concerns have been raised about its construct validity and so this study seeks to examine this and other psychometric aspects of both the DASH and QuickDASH from a modern test theory perspective. METHODS: Participants in the study were eligible if they had a confirmed diagnosis of Rheumatoid Arthritis (RA). They were mailed a questionnaire booklet which included the DASH. Construct validity was examined by fit to the Rasch measurement model. The degree of precision of both the DASH and QuickDASH were considered through their Standard Error of Measurement (SEM). RESULTS: Three hundred and thirty-seven subjects with confirmed RA took part, with a mean age of 62.0 years (SD12.1); 73.6% (n = 252) were female. The median standardized score on the DASH was 33 (IQR 17.5-55.0). Significant misfit of the DASH and QuickDASH was observed but, after accommodating local dependency among items in a two-testlet solution, satisfactory fit was obtained, supporting the unidimensionality of the total sets and the sufficiency of the raw (ordinal or standardized) scores. CONCLUSION: Having accommodated local response dependency in the DASH and QuickDASH item sets, their total scores are shown to be valid, given they satisfy the Rasch model assumptions. The Rasch transformation should be used whenever all items are used to calculate a change score, or to apply parametric statistics within an RA population. SIGNIFICANCE AND INNOVATIONS: Most previous modern psychometric analyses of both the DASH and QuickDASH have failed to fully address the effect of a breach of the local independence assumption upon construct validity. Accommodating this problem by creating 'super items' or testlets, removes this effect and shows that both versions of the scale are valid and unidimensional, as applied with a bi-factor equivalent solution to an RA population. The Standard Error of Measurement of a scale can be biased by failing to take into account the local dependency in the data which inflates reliability and thus making the SEM appear better (i.e. smaller) than the true value without bias.

Development and validation of Spasticity Index-Amyotrophic Lateral Sclerosis.

OBJECTIVES: Spasticity is a common and disabling feature of amyotrophic lateral sclerosis (ALS). There are currently no validated ALS-specific measures of spasticity. The aim of this study was to develop and use a self-report outcome measure for spasticity in ALS. METHODS: Following semi-structured interviews with 11 ALS patients, a draft scale was administered across ALS clinics in the UK. Internal validity of the scale was examined using the Rasch model. The numerical rating scale (NRS) for spasticity and Leeds Spasticity scale (LSS) were co-administered. The final scale was used in a path model of spasticity and quality of life. RESULTS: A total of 465 patients (mean age 64.7 years (SD 10), 59% male) with ALS participated. Spasticity was reported by 80% of subjects. A pool of 71 items representing main themes of physical symptoms, negative impact and modifying factors was subject to an iterative process of item reduction by Rasch analysis resulting in a 20-item scale-the Spasticity Index for ALS (SI-ALS)-which was unidimensional and free from differential item functioning. Moderate correlations were found with LSS and NRS-spasticity. Incorporating the latent estimate of spasticity into a path model, greater spasticity reduced quality of life and motor function; higher motor function was associated with better quality of life. CONCLUSIONS: The SI-ALS is a disease-specific self-report scale, which provides a robust interval-level measure of spasticity in ALS. Spasticity has a substantial impact on quality of life in ALS.

A study of the internal construct and predictive validity of the SMART assessment for emergence from vegetative state.

OBJECTIVE: The Sensory Modality Assessment and Rehabilitation Technique (SMART) was developed to assess the levels of awareness, functional, sensory and communicative abilities of adults in vegetative (VS) or minimally-conscious states following severe brain injury. The current study seeks to ascertain if a total score can be derived from the individual assessments contained within SMART and to test the internal construct and predictive validity of that total score. SUBJECTS: Persons in VS were recruited over a 3-year period and current status was determined after a 17-year follow-up. DESIGN: Data were evaluated by fit to the Rasch model. Predictive validity for emergence from VS was ascertained through an Area-Under-the-Curve [AUC] analysis. RESULTS: Sixty people in VS were assessed on several occasions. Average age on admission was 38.8 years; 30 had anoxic brain damage; 21 traumatic injury. The Rasch analysis indicated the raw score was a sufficient statistic for awareness. Over half [55%] failed to emerge from VS. For those with anoxic brain injury, a SMART cut point of 85 gave an AUC of 0.966 (95% CI = 0.910-1.00) for emergence, as did a cut point of 68 for those with traumatic brain injury. DISCUSSION: The current analysis suggests that SMART may have important predictive attributes for emergence (or lack thereof). No change in status of those discharged in VS has been reported to this present day.

The Manual Work Instability Scale: development and validation.

BACKGROUND: Increasing awareness of the burden of absenteeism and reduced performance at work highlights the importance of early identification of individuals experiencing work instability (WI), a mismatch between functional and cognitive abilities and job demands. AIMS: To develop and validate a screening questionnaire to measure WI in manual workers. METHODS: Questionnaire items were generated via qualitative interviews with manual workers and a draft survey instrument was completed by workers in a variety of fields. Rasch analysis was used interactively to assess the psychometric aspects of the emerging scale, including unidimensionality and absence of item bias (differential item functioning). RESULTS: A total of 17 qualitative interviews generated 110 potential items for the questionnaire. The item set resolved to a 25-item scale, which satisfied model expectations (item residual mean = -0.13, SD = 1.04; person residual mean = -0.29, SD = 0.75), had good reliability (alpha = 0.86) and strict unidimensionality (t-test 7.5% confidence interval 3.8-11.2). CONCLUSIONS: The Manual Work Instability Scale is a short psychometrically robust questionnaire based on the concept of WI, which incorporates both musculoskeletal symptoms and relevant psychosocial factors. It may prove effective in screening and identifying WI in workers in predominantly physical occupations.

Staff burnout in paediatric oncology: new tools to facilitate the development and evaluation of effective interventions.

Working in paediatric oncology can be stressful, and staff may need support if they are to avoid burnout, but there is currently no evidence base to guide the development of interventions. As a significant barrier to addressing this gap is a lack of context specific research instruments, a project was undertaken to develop measures of the stressors and rewards experienced by staff. Measure development involved: (1) qualitative interviews with a purposive sample of paediatric oncology staff to develop an 'item pool' (n = 32); (2) selection of items for draft measures; (3) cognitive interviews (n = 7) to gather feedback on draft measures; (4) a survey of staff (n = 203) using the draft and comparator measures; (5) factor and Rasch analysis to determine the scaling properties of the measures; (6) an assessment of construct validity. As a result, the Work Stressors Scale - Paediatric Oncology (WSS-PO) and the Work Rewards Scale - Paediatric Oncology (WRS-PO) were created. Both measures have considerable content validity, and fulfil classical test theory requirements and Rasch model requirements for an interval level scale. These new measures can be used in research and clinical practice to investigate factors associated with burnout, and to facilitate and direct the development of staff interventions.

Perceived changes and minimum clinically important difference of the Neurological Fatigue Index for multiple sclerosis (NFI-MS).

The determination of the minimum clinically important difference (MCID) is an important aspect of scale development. The Neurological Fatigue Index for multiple sclerosis (NFI-MS) was administered before and after expected change or stability in fatigue in 208 multiple sclerosis (MS) patients. The overall change scores of the NFI-MS accorded with perceived direction of change; importantly, no change was seen when none was perceived. Using the interval level NFI-MS scores, the largest MCID equated to 2.49 points on the Summary scale, 2.36 points on the Physical scale, 0.84 points on the Cognitive scale, 0.97 on the Diurnal Sleep scale and 1.95 on the Nocturnal Sleep scale. Our conclusion is that the NFI-MS responds as expected to changes in fatigue and has desirably small MCID scores.

Is the Epworth sleepiness scale suitable for use in stroke?

BACKGROUND: The Epworth Sleepiness Scale (ESS-8) is frequently used in stroke but has never been validated for this condition. There is concern regarding the suitability of the driving item (item 8). A summed raw score of 10 or more (from a maximum of 24) signifies pathological sleepiness. OBJECTIVE: To determine the construct validity of the ESS-8 by Rasch analysis and in particular to determine whether omission of item 8 confounds the scale. METHOD: A pack containing the ESS-8 and questions regarding sleep and demographics was sent to 999 patients who had experienced a stroke within the past 4 years. Data were assessed for fit to the Rasch model. RESULTS: Analysis of 269 records revealed a unidimensional scale that was free from differential item functioning by age and sex with good overall fit to the Rasch model. Item 4 had disordered thresholds. Analysis of the ESS without item 8 (ESS-7) also revealed a valid scale. Equating person locations between the ESS-8 and ESS-7 showed no differences below a summed raw score of 18. CONCLUSION: The ESS-8 has good construct validity for use in stroke and is reliable at the cutpoint of 10. Summed raw scores below 18 will be unaffected if nondrivers either score as zero or simply omit item 8. The scale is therefore robust for detecting cases of pathological sleepiness in stroke but may not be suitable for measuring high levels of sleepiness in a sample containing both drivers and nondrivers. Instead, the ESS-7 could be used for this purpose.

Prevalence of depression in amyotrophic lateral sclerosis/motor neuron disease: multi-attribute ascertainment and trajectories over 30 months.

Objective: Evidence is equivocal about the prevalence of depression in amyotrophic lateral sclerosis (ALS). This study uses a multi-attribute ascertainment of the prevalence of depression and examines this prevalence over time. Methods: Patients with ALS were recruited into the Trajectories of Outcome in Neurological Conditions (TONiC-ALS) study. Caseness was identified by the Modified-Hospital Anxiety and Depression Scale (M-HADS). In addition, participants provided data on co-morbidities and medication use. A combination of the three was used to derive the estimate for the prevalence of depression, treated or untreated. Longitudinal data were analyzed by trajectory analysis of interval level M-HADS-Depression data. Results: Among 1120 participants, the mean age was 65.0 years (SD 10.7), 60.4% male, and the median duration since diagnosis was 9 months (IQR 4-24). Caseness of probable depression at baseline, defined by M-HADS-Depression, was 6.45% (95%CI: 5.1-8.0). Taken together with antidepressant medication and co-morbidity data, the prevalence of depression was 23.1% (95%CI: 20.7-25.6). Of those with depression, 17.8% were untreated. Trajectory analysis identified three groups, one of which contained the most cases; the level of depression for each group remained almost constant over time. Conclusion: Depression affects almost a quarter of those with ALS, largely confined to a single trajectory group. Prevalence estimates based on screening for current depressive symptoms substantially under-estimate the population experiencing depression. Future prevalence studies should differentiate data based on current symptoms from those including treated patients. Both have their place in assessing depression and the response by the health care system, including medication, depending upon the hypothesis under test.

The unidimensional self-efficacy scale for MS (USE-MS): developing a patient based and patient reported outcome.

BACKGROUND: Self-efficacy concerns the individual's belief that he or she is capable of performing a certain task and producing a desired effect, i.e. it reflects the person's perceptions of their capability for specific tasks, as distinct from their actual ability. Self-efficacy has been shown to influence motivation, psychological well-being, adherence with treatment regimes and quality of life in multiple sclerosis and other conditions. OBJECTIVE: To develop a unidimensional scale of MS self-efficacy with robust psychometric properties, suitable for patient self report. METHODS: A questionnaire pack covering three MS self-efficacy scales, the Dispositional Resilience Scale and demographic data was posted to MS patients from two MS databases. Data underwent Rasch analysis. RESULTS: Response rate was 309/600 (51.5%). None of the existing MS self-efficacy scales were unidimensional. A new 12-item scale, created by combining items from our two scales, was shown to fit the Rasch model, was unidimensional, and invariant for gender, education and disease duration. CONCLUSION: The Unidimensional Self-Efficacy scale for MS (USE-MS) provides a simple summated scale for an ordinal estimate of a persons' self efficacy. A transformation to interval scaling is available for use in the calculation of change scores and effect sizes.

Development of a patient reported outcome measure for fatigue in motor neurone disease: the Neurological Fatigue Index (NFI-MND).

BACKGROUND: The objective of this research was to develop a disease-specific measure for fatigue in patients with motor neurone disease (MND) by generating data that would fit the Rasch measurement model. Fatigue was defined as reversible motor weakness and whole-body tiredness that was predominantly brought on by muscular exertion and was partially relieved by rest. METHODS: Qualitative interviews were undertaken to confirm the suitability of a previously identified set of 52 neurological fatigue items as relevant to patients with MND. Patients were recruited from five U.K. MND clinics. Questionnaires were administered during clinic or by post. A sub-sample of patients completed the questionnaire again after 2-4 weeks to assess test-retest validity. Exploratory factor analyses and Rasch analysis were conducted on the item set. RESULTS: Qualitative interviews with ten MND patients confirmed the suitability of 52 previously identified neurological fatigue items as relevant to patients with MND. 298 patients consented to completing the initial questionnaire including this item set, with an additional 78 patients completing the questionnaire a second time after 4-6 weeks. Exploratory Factor Analysis identified five potential subscales that could be conceptualised as representing: 'Energy', 'Reversible muscular weakness' (shortened to 'Weakness'), 'Concentration', 'Effects of heat' and 'Rest'. Of the original five factors, two factors 'Energy' and 'Weakness' met the expectations of the Rasch model. A higher order fatigue summary scale, consisting of items from the 'Energy' and 'Weakness' subscales, was found to fit the Rasch model and have acceptable unidimensionality. The two scales and the higher order summary scale were shown to fulfil model expectations, including assumptions of unidimensionality, local independency and an absence of differential item functioning. CONCLUSIONS: The Neurological Fatigue Index for MND (NFI-MND) is a simple, easy-to-administer fatigue scale. It consists of an 8-item fatigue summary scale in addition to separate scales for measuring fatigue experienced as reversible muscular weakness and fatigue expressed as feelings of low energy and whole body tiredness. The underlying two factor structure supports the patient concept of fatigue derived from qualitative interviews in this population. All three scales were shown to be reliable and capable of interval level measurement.

Construct Validity of the Holistic Complementary and Alternative Medicines Questionnaire (HCAMQ)-An Investigation Using Modern Psychometric Approaches.

The scientific basis of efficacy studies of complementary medicine requires the availability of validated measures. The Holistic Complementary and Alternative Medicine Questionnaire (HCAMQ) is one such measure. This article aimed to examine its construct validity, using a modern psychometric approach. The HCAMQ was completed by 221 patients (mean age 66.8, SD 8.29, 58% females) with chronic stable pain predominantly from a single joint (hip or knee) of mechanical origin, waiting for a hip (40%) or knee (60%) joint replacement, on enrolment in a study investigating the effects of acupuncture and placebo controls. The HCAMQ contains a Holistic Health (HH) Subscale (five items) and a CAM subscale (six items). Validity of the subscales was tested using Cronbach alpha's, factor analysis, Mokken scaling and Rasch analysis, which did not support the original two-factor structure of the scale. A five-item HH subscale and a four-item CAM subscale (worded in a negative direction) fitted the Rasch model and were unidimensional (χ2 = 8.44, P = 0.39, PSI = 0.69 versus χ2 = 17.33, P = 0.03, PSI = 0.77). Two CAM items (worded in the positive direction) had significant misfit. In conclusion, we have shown that the original two-factor structure of the HCAMQ could not be supported but that two valid shortened subscales can be used, one for HH Beliefs (four-item HH), and the other for CAM Beliefs (four-item CAM). It is recommended that consideration is given to rewording the two discarded positively worded CAM questions to enhance construct validity.

Measuring coping in people with amyotrophic lateral sclerosis using the Coping Index-ALS: A patient derived, Rasch compliant scale.

OBJECTIVE: The progressively disabling and terminal nature of ALS/MND imposes major coping demands on patients. We wished to improve the psychometric properties of our previously published MND-Coping Scale, so that parametric analyses were valid, and to make it simpler for patients to complete and clinicians to score. METHODS: After a new qualitative analysis of 26 patients with ALS/MND, the draft Coping Index-ALS (CI-ALS) was administered to 465 additional patients, alongside COPE-60, General Perceived Self Efficacy scale, and WHOQOL-BREF. Validity of the CI-ALS was assessed using the Rasch model. External validity was checked against comparator measures. RESULTS: Thirteen centres contributed 465 patients, mean age 64.9 years (SD 10.8), mean disease duration 28.4 months (SD 37.5). The CI-ALS-Self and CI-ALS-Others both satisfied Rasch model expectations and showed invariance across age, gender, marital status and type of onset. Expected correlations were observed with comparator scales. A nomogram is available to convert the raw scores to interval level measures suitable for parametric analysis. CONCLUSIONS: Coping abilities in ALS/MND can now be measured using a simple 21 item self-report measure, offering two subscales with a focus of 'coping by self ' and 'coping with others'. This allows clinicians to identify individuals with poor coping and facilitates research on interventions that may improve coping skills.

Rasch analysis of the Modified Fatigue Impact Scale (MFIS) in multiple sclerosis.

BACKGROUND: The 21-item Modified Fatigue Impact Scale (MFIS) has been recommended as an outcome measure for use in multiple sclerosis and is commonly used to generate an overall score of fatigue. OBJECTIVE: To test if the MFIS total score is valid by application of the Rasch measurement model. METHOD: The MFIS was sent by post to patients with clinically definite multiple sclerosis in two centres in the UK. Data were fitted to the Rasch model. RESULTS: Analysis was based on 415 records (55% response). The 21-item scale did not fit the Rasch model mainly because of multidimensionality. The scale was found to contain a "physical" dimension and a "cognitive" dimension, consistent with the original subscale structure. Valid physical and cognitive subscales were derived after deletion of some items. CONCLUSION: The MFIS cannot be used to generate a single overall score of fatigue. The conceptual interaction between the two dimensions remains unclear, which poses problems when interpreting change scores in these individual scales. Studies in which a global MFIS score was used as either an outcome measure or selection tool may need to be re-evaluated.

The development of the L-QoL: a quality-of-life instrument specific to systemic lupus erythematosus.

OBJECTIVES: Complex diseases, such as systemic lupus erythematosus (SLE), present dilemmas over choice of outcome measures. Using a battery of instruments to capture the impact of different impairments or activity limitations experienced does not provide assessment of the wider impact on quality of life (QoL). This paper describes the development and testing of a new instrument to measure QoL in systemic lupus erythematosus (L-QoL). METHODS: The development combines theoretical strengths of the needs-based QoL model with statistical and diagnostic powers of the Rasch model. Content was derived from in-depth interviews with relevant patients. Cognitive debriefing interviews assessed face and content validity. Rasch analysis was applied to data from an initial postal survey to remove misfitting items. A second postal survey assessed scaling properties, reliability, internal consistency and validity. RESULTS: A 55-item questionnaire was derived from interview transcripts. Cognitive debriefing confirmed acceptability. Rasch analysis of postal survey data (n = 95) removed misfitting items. A second postal survey (n = 93), produced a 25-item version with good item fit and stability, excellent test-retest reliability (0.92), internal consistency (0.92) and strict unidimensionality. CONCLUSIONS: It is concluded that the L-QoL should prove a valuable instrument for assessing patient-based outcome in clinical trials and practice.

Adaptation and cross-cultural validation of the rheumatoid arthritis work instability scale (RA-WIS).

BACKGROUND: Despite recent advances, work disability in rheumatoid arthritis (RA) remains common. Work disability is frequently preceded by a period of work instability characterised by a mismatch between an individual's functional abilities and job demands. This could raise the risk of work disability if not resolved. A work instability scale for RA (RA-WIS) has previously been developed to screen for this risk. The objective of this study was the adaptation of this scale into French, Dutch and German. METHOD: Different language versions of the RA-WIS were produced through a process of forward and back translations. The new scales were tested for face validity. English data from the original developmental study was pooled with data generated through postal surveys in each country. The internal construct and cross-cultural validity of the new scales were assessed using Rasch analysis, including differential item functioning (DIF) by culture. RESULTS: The pooled data showed good fit to the Rasch model and demonstrated strict unidimensionality. DIF was found to be present for six items, but these appeared both to cancel out at the test level and have only a marginal effect on the test score itself. CONCLUSIONS: The RA-WIS was shown to be robust to adaptation into different languages. Data fitted Rasch model expectations and strict tests of unidimensionality. This project and the continuing work on further cross-cultural adaptations have the potential to help ensure clinicians across Europe are able to support RA patients to achieve their potential in work through early identification of those most at risk.

Modification and validation of the Lysholm Knee Scale to assess articular cartilage damage.

OBJECTIVE: The Lysholm Knee Scale is an 8-item questionnaire originally designed as an outcome measure for ligament reconstruction but is commonly used as a measure for knee chondral damage. This study tests the scale's internal construct validity using the Rasch model, a measurement model which sets strict standards for the quality of measurement derived from the scale. The study also investigates the level of agreement between scores from patients and physiotherapists; and reviews the present weighting system. DESIGN: One hundred and fifty-seven patients with knee chondral damage awaiting surgery completed the Lysholm as part of a multicentre clinical trial based in 16 UK and two Norwegian hospitals. The patients were assessed by a physiotherapist who independently completed the Lysholm on the same day. RESULTS: Fit to the Rasch model was achieved [mean item fit -0.26, standard deviation (SD) 1.01] after removal of one item (Swelling). With no differential item functioning (DIF) by rater, the intraclass correlation coefficient was 0.9 [95% confidence interval (CI): 0.86-0.93] and a Bland-Altman plot showed no consistent difference in rating. CONCLUSIONS: The Lysholm Knee Scale satisfies Rasch model expectations after removal of the swelling item. Generally there is a high degree of agreement between the patient and professional ratings. By removing the swelling item and using unweighted scores, a modified version of the Lysholm Knee Scale is recommended as an outcome measure for knee chondral damage.