Reliability and construct validity of the ACTIVLIM-Hemo and Haemophilia Activities List (HAL) questionnaires in individuals with haemophilia.

OBJECTIVE: The objective of this study is to assess the reliability and construct validity of ACTIVLIM-Hemo, a newly developed Rasch-built questionnaire designed to evaluate activity limitations in people with haemophilia (PwH), in comparison with the Haemophilia Activities List (HAL), which was developed using Classical Test Theory. METHODS: A total of 130 participants with haemophilia A or B were included. They underwent various assessments, including joint health scoring (HJHS), functional tests (TUG and 2MWT) and completed questionnaires such as the BPI, IPAQ, HAL and ACTIVLIM-Hemo. Reliability indices and the minimum detectable change (MDC95) were determined for ACTIVLIM-Hemo and for HAL. Construct validity was evaluated through correlations and multiple linear regression, considering demographic and clinical factors. RESULTS: Both ACTIVLIM-Hemo (Person Separation Index = 0.92) and HAL (Cronbach's α = 0.98) demonstrated high reliability. The MDC95 for ACTIVLIM-Hemo represented 11.6% of its measurement range, while for HAL, it amounted to 18/100 score points. Activity limitations measured by both instruments were significantly correlated with demographic and clinical factors. Joint health (HJHS), pain severity (BPI) and walking performance (2MWT) emerged as the main predictors of activity limitations, explaining 75% of the variance in ACTIVLIM-Hemo and 60% in HAL. CONCLUSION: ACTIVLIM-Hemo stands as a reliable and valid instrument for assessing activity limitations in PwH. Both instruments exhibited significant correlations with demographic and clinical factors, but ACTIVLIM-Hemo displayed a more homogeneous construct. Given its linear scale and lower MDC95 and better targeting, ACTIVLIM-Hemo shows promise as a patient-centric instrument for assessing responsiveness to treatment during individual follow-up.

ACTIVLIM-Hemo: A new self-reported, unidimensional and linear measure of activity limitations in persons with haemophilia.

INTRODUCTION: To assess activity limitations in people with haemophilia (PwH), the self-reported Haemophilia Activity List (HAL) is widely employed, despite several methodological limitations impacting the interpretation of categorical scores. Modern psychometric approaches avoid these limitations by using a probabilistic model, such as the Rasch model. The ACTIVLIM is a Rasch-built measurement of activity limitations previously validated in several clinical conditions like neuromuscular disorders. AIMS: This study sought to develop the ACTIVLIM-Hemo, meaning an ACTIVLIM scale version specifically adapted to assess daily activity limitations in adult PwH. METHODS: Daily activities were assessed as "impossible," "difficult" or "easy" by 114 PwH (median age of 44 years) with 63 of them reassessed after 12 days. The Rasch Rating Scale model was used to identify activities delineating a unidimensional and linear scale unbiased by demographic and clinical status. Concurrent validity was determined through correlation with the HAL sub-scores and sum score. RESULTS: The ACTIVLIM-Hemo included 22 pertinent activities, with difficulties independent of demographic and clinical conditions, allowing a reliable measure of activity limitations (PSI = .92) expressed on a linear and unidimensional scale in PwH (7%-100 % range, ceiling effect of 1/114) with excellent test-retest reliability (ICC = .978). Spearman rank correlations between ACTIVLIM-Hemo and HAL sub-scores ranged between .623 and .869. CONCLUSIONS: The ACTIVLIM-Hemo is an easy-to-administer, valid and reliable alternative to HAL in assessing activity limitations in PwH. Its invariant scale can be used across conditions and time to compare the functional status of PwH over a wide measurement range.

Recognizing Manual Activities Using Wearable Inertial Measurement Units: Clinical Application for Outcome Measurement.

The ability to monitor activities of daily living in the natural environments of patients could become a valuable tool for various clinical applications. In this paper, we show that a simple algorithm is capable of classifying manual activities of daily living (ADL) into categories using data from wrist- and finger-worn sensors. Six participants without pathology of the upper limb performed 14 ADL. Gyroscope signals were used to analyze the angular velocity pattern for each activity. The elaboration of the algorithm was based on the examination of the activity at the different levels (hand, fingers and wrist) and the relationship between them for the duration of the activity. A leave-one-out cross-validation was used to validate our algorithm. The algorithm allowed the classification of manual activities into five different categories through three consecutive steps, based on hands ratio (i.e., activity of one or both hands) and fingers-to-wrist ratio (i.e., finger movement independently of the wrist). On average, the algorithm made the correct classification in 87.4% of cases. The proposed algorithm has a high overall accuracy, yet its computational complexity is very low as it involves only averages and ratios.

Lower Limb Kinematics Using Inertial Sensors during Locomotion: Accuracy and Reproducibility of Joint Angle Calculations with Different Sensor-to-Segment Calibrations.

Inertial measurement unit (IMU) records of human movement can be converted into joint angles using a sensor-to-segment calibration, also called functional calibration. This study aims to compare the accuracy and reproducibility of four functional calibration procedures for the 3D tracking of the lower limb joint angles of young healthy individuals in gait. Three methods based on segment rotations and one on segment accelerations were used to compare IMU records with an optical system for their accuracy and reproducibility. The squat functional calibration movement, offering a low range of motion of the shank, provided the least accurate measurements. A comparable accuracy was obtained in other methods with a root mean square error below 3.6° and an absolute difference in amplitude below 3.4°. The reproducibility was excellent in the sagittal plane (intra-class correlation coefficient (ICC) > 0.91, standard error of measurement (SEM) < 1.1°), good to excellent in the transverse plane (ICC > 0.87, SEM < 1.1°), and good in the frontal plane (ICC > 0.63, SEM < 1.2°). The better accuracy for proximal joints in calibration movements using segment rotations was traded to distal joints in calibration movements using segment accelerations. These results encourage further applications of IMU systems in unconstrained rehabilitative contexts.

Determinants of Social Participation at 1, 3, and 6 Months Poststroke in Benin.

OBJECTIVE: To build a model of prediction of social participation of community-dwelling stroke survivors in Benin at 1 month, 3 months, and 6 months. DESIGN: An observational study with evaluations at 1 month, 3 months, and 6 months poststroke. Correlational analyses and multivariate linear regressions were performed. SETTING: Outpatient rehabilitation centers in Benin. PARTICIPANTS: A volunteer sample of 91 stroke patients was enrolled at baseline; 64 (70%) patients completed all the study (N=64): 70% male and 52% right hemiparesis. INTERVENTION: Not applicable. MAIN OUTCOME MEASURES: Participants were evaluated with the Participation Measurement Scale, ACTIVLIM-Stroke (activities of daily living [ADL]), Stroke Impairment Assessment Set, 6-minute walk test, Hospital Anxiety and Depression Scale, and the modified Rankin Scale. RESULTS: The significant predictors of social participation after controlling the confounders were the following: at 1 month ADL (0.4 [0.3, 0.6]) and depression (‒0.6 [‒0.8, ‒0.2]) with total model R2=0.44; at 3 months ADL (0.58 [0.4, 0.7]) and depression (‒0.58 [‒0.5, ‒0.7]) with total model R2=0.65; and at 6 months ADL (0.31 [0.2, 0.5]), impairments (‒0.82 [‒0.5, ‒0.7]), and depression (‒0.94 [‒0.8, ‒0.2]) with total model R2=0.78. CONCLUSIONS: Using socioculturally tailored tools, the present study identified ADL performance (ACTIVLIM-Stroke), depression (Hospital Anxiety Depression Scale), and overall impairments (Stroke Impairment Assessment Set) as the significant determinants of social participation (Participation Measurement Scale) poststroke in Benin. These findings will be a valuable resource for rehabilitation stakeholders in evaluating interventions, programs, and policies designed to encourage social participation for stroke patients.

Measuring Participation After Stroke in Africa: Development of the Participation Measurement Scale.

OBJECTIVE: To develop a valid stroke-specific tool, named the Participation Measurement Scale (PM-Scale), for the measurement of participation after stroke. DESIGN: Observational study and questionnaire development. SETTING: Outpatient rehabilitation centers. PARTICIPANTS: Patients with stroke (N=276; mean age, 58.5±11.1y; 57% men). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Participants completed a 100-item experimental questionnaire of the PM-Scale. Items were scored as "not at all," "weakly," or "strongly." The Hospital Anxiety and Depression Scale was used to evaluate depression, and the modified Rankin Scale was used to categorize the severity of disability on the basis of observation. RESULTS: After successive Rasch analyses using unrestricted partial credit parameterization, a valid, unidimensional, and linear 22-item scale for the measurement of participation was constructed. All 22 items fulfilled the measurement requirements of overall and individual item and person fits, category discrimination, invariance, and local response independence. The PM-Scale showed good internal consistency (person separation index, .93). The test-retest reliability of item difficulty hierarchy (r=.96; P<.001) and patient location (r=.99; P<.001) were excellent. This patient-based scale covers all 9 International Classification of Functioning, Disability and Health domains of participation. CONCLUSIONS: The PM-Scale has good psychometric qualities and provides accurate measures of participation in patients with stroke in Africa.

Normative values in healthy adults for the 6-minute and 2-minute walk tests in Belgium and Vietnam: implications for clinical practice.

OBJECTIVE: To establish reference values for the 6-minute walk test (6MWT) and 2-minute walk test (2MWT) distances, to investigate the correlation between these 2 tests, and to establish prediction equations for these distances in healthy populations of Belgium and Vietnam. DESIGN: Cross-sectional study. SUBJECTS AND METHODS: The 6MWT and 2MWT were administered to a convenience sample of 239 Belgian and 303 Vietnamese participants between the ages of 18 and 80 years. RESULTS: The mean (standard deviation; SD) 2MWT distances were 215 (32.8) m for Belgian participants and 156 (25.5) m for Vietnamese participants. The mean (SD) 6MWT distances were 625 (90.7) m for Belgian participants and 449 (70.4) m for Vietnamese participants. The Pearson correlation coefficient between the 2 tests was 0.901 (p < 0.001) for Belgian participants and 0.871 (p < 0.001) for Vietnamese participants. Age and sex were the 2 most important predictors of walking distance, followed by body mass index for Belgium and height for Vietnam. The adjusted R² ranged from 0.31 to 0.49 across 4 predictive equations. CONCLUSION: These results can be used to determine the presence of walking performance deficits and to guide future studies. The 2MWT is suggested as a useful and convenient alternative to the 6MWT for assessing walking performance in clinical practice.

Validation of the ABILHAND questionnaire to measure manual ability in children and adults with neuromuscular disorders.

BACKGROUND: Neuromuscular disorders (NMDs) can lead to specific manual disabilities due to hand muscle weakness and atrophy, myotonia or loss of sensory function. The aim of this study was to adapt and validate the ABILHAND questionnaire in children and adults with NMDs using the Rasch model. METHODS: This questionnaire contained specific manual activities for children and for adults, as well as common manual activities. 124 adult patients and the parents of 124 paediatric patients were asked to provide their perceived difficulty in performing each manual activity on a three level scale: impossible (0), difficult (1) or easy (2). Items were selected from well established psychometric criteria (ordered categories, equal item discrimination, adequate fit to the Rasch model, lack of redundancy) using the Rasch Unidimensional Measurement Models (RUMM2020) computer programme. RESULTS: The 22 selected items contain four children specific items, four adult specific items and 14 items commonly applicable to both children and adults. They define a unidimensional and linear measure of manual ability and demonstrate continuous progression in their difficulty. The item hierarchy of difficulty was invariant across six patient related factors. The scale exhibited good precision (r=0.95) and the 22 items were well targeted to the patients' locations. The ABILHAND measures were strongly related to the ACTIVLIM measures (r=0.76) and poorly related to grip strength (r=0.36 for the right hand and r=0.40 for the left hand). CONCLUSION: This scale can be used for adults and children, allowing manual ability to be assessed from childhood to adulthood.

Manual ability in hand surgery patients: Validation of the ABILHAND scale in four diagnostic groups.

BACKGROUND: Patients treated in hand surgery (HS) belong to different demographic groups and have varying impairments related to different pathologies. HS outcomes are measured to assess treatment results, complication risks and intervention reliability. A one-dimensional and linear measure would allow for unbiased comparisons of manual ability between patients and different treatment effects. OBJECTIVE: To adapt the ABILHAND questionnaire through Rasch analysis for specific use in HS patients and to examine its validity. METHODS: A preliminary 90-item questionnaire was presented to 216 patients representing the diagnoses most frequently encountered in HS, including distal radius fracture (n = 74), basal thumb arthritis (n = 66), carpal tunnel syndrome (n = 53), and heavy wrist surgery (n = 23). Patients were assessed during the early recovery and in the late follow-up period (0-3 months, 3-6 months and >6 months), leading to a total of 305 assessments. They rated their perceived difficulty with queried activities as impossible, difficult, or easy. Responses were analyzed using the RUMM2030 software. Items were refined based on item-patient targeting, fit statistics, differential item functioning, local independence and item redundancy. Patients also completed the QuickDASH, 12-item Short Form Survey (SF-12) and a numerical pain scale. RESULTS: The rating scale Rasch model was used to select 23 mostly bimanual items on a 3-level scale, which constitute a unidimensional, linear measure of manual ability with good reliability across all included diagnostic groups (Person-Separation Index = 0.90). The resulting scale was found to be invariant across demographic and clinical subgroups and over time. ABILHAND-HS patient measures correlated significantly (p<0.001) with the QuickDASH (r = -0.77), SF-12 Physical Component Summary (r = 0.56), SF-12 Mental Component Summary (r = 0.31), and pain scale (r = -0.49). CONCLUSION: ABILHAND-HS is a robust person-centered measure of manual ability in HS patients.

A robust machine learning enabled decomposition of shear ground reaction forces during the double contact phase of walking.

BACKGROUND: Dynamic analyses of walking rely on the 3D ground reaction forces (GRF) under each foot, while only the resultant force of both limbs may be recorded on a single-belt instrumented treadmill or when both feet touch the same force platform. RESEARCH QUESTION: This study aims to develop a robust decomposition of the shear GRF to complete the most accurate decomposition of the vertical GRF [8]. METHODS: A retrospective study of 374 healthy adults records (age: 22.8 ±â€¯2.6 years, speed: 1.34 ±â€¯0.28 m/s) and of 434 patient records (age: 21.3 ±â€¯17.8 years, speed: 0.64 ±â€¯0.19 m/s) were used in a machine learning process to develop a robust predictive model to decompose the fore-aft GRF. The lateral GRF was decomposed by resolving the equilibrium of transverse moments around the center of pressure. RESULTS: A predictive linear model of the fore-aft GRF under the back foot every 5% of the double contact phase was obtained from 2 predictors: the total fore-aft GRF and the vertical GRF under the back foot. Each predictor uses a time series of 31 samples before and during the double contact. The model performs accurately in healthy (median[IQR] error of 3.0[2.2-4.1]%) and in clinical gaits (7.7[4.7-13.4]%). The error in lateral GRF decomposition is of 5.7[3.9-10.2]% in healthy gaits and of 12.0[7.2-19.2]% in patients under the back foot and about half of that under the front foot. SIGNIFICANCE: The decomposition of shear GRFs achieved in this study supports the mechanics of walking. It provides outstanding accuracy in healthy gait and also applies to neurologic and orthopedic disorders. Together with the vertical GRF decomposition [8], this approach for the shear components paves the way for robust single limb GRF determination on a single-belt instrumented treadmill or when both feet touch the same force platform in normal and clinical gait analysis.

Hand impairments and their relationship with manual ability in children with cerebral palsy.

OBJECTIVE: To study hand impairments and their relationship with manual ability in children with cerebral palsy. DESIGN: Cross-sectional survey. PATIENTS: A total of 101 children with cerebral palsy (mean age 10 years, age range 6-15 years) were assessed. METHODS: Three motor and 3 sensory impairments were measured on both hands. Motor impairments included grip strength (Jamar dynamometer), gross manual dexterity(Box and Block Test) and fine finger dexterity (Purdue Peg-board Test). Sensory impairments included tactile pressure detection (Semmes-Weinstein aesthesiometer), stereognosis(Manual Form Perception Test) and proprioception (passive mobilization of the metacarpophalangeal joints). Manual ability was measured with the ABILHAND-Kids questionnaire. The relationship between hand impairments and manual ability was studied through correlation coefficients and a multiple linear forward stepwise regression analysis. RESULTS: Motor impairments were markedly more prevalent than sensory ones. Gross manual dexterity on the dominant hand and grip strength on the non-dominant hand were the best independent predictors of the children's manual ability,predicting 58% of its variance. CONCLUSION: Hand impairments and manual ability are not related in a predictable straightforward relationship. It is important that, besides hand impairments, manual ability is also measured and treated, as it is not simply the integration of hand functions in daily activities.

How robust is ACTIVLIM for the follow-up of activity limitations in patients with neuromuscular diseases?

This study aims to investigate the clinimetric properties of ACTIVLIM, a measure of activity limitations, when it is used in daily practice in a large nationwide representative cohort of patients with neuromuscular diseases. A cohort of 2986 patients was assessed at least once over 2 years in 6 national neuromuscular diseases reference centers. Successive Rasch analyses were conducted in order to investigate the scale validity, reliability, consistency across demographic and clinical sub-groups and its sensitivity to change. ACTIVLIM confirmed excellent fit to a unidimensional scale, with stable but 3-times more accurate item calibrations compared to the original publication. It showed a good reliability (R = 0.95), an appropriate targeting for 87% of the sample and an excellent invariance across age, gender, language and time. Despite some variations in the item difficulty hierarchy across diagnoses, ACTIVLIM exhibited a good capability to quantify small but significant changes in activity for various diagnostic groups. Overall, ACTIVLIM demonstrated very good clinimetric properties, allowing accurate quantitative measurement of activity limitations in both children and adults with a variety of neuromuscular diseases.

Cross-cultural validity of functional independence measure items in stroke: a study using Rasch analysis.

OBJECTIVE: To analyse cross-cultural validity of the Functional Independence Measure (FIM) in patients with stroke using the Rasch model. SETTINGS: Thirty-one rehabilitation facilities within 6 different countries in Europe. PARTICIPANTS: A total of 2546 in-patients at admission, median age 63 years. METHODS: Data from the FIM were evaluated with the Rasch model, using the Rasch analysis package RUMM2020. A detailed analysis of scoring functions of the 7 categories of the FIM items was undertaken prior to testing fit to the model. Categories were re-scored where necessary. Analysis of Differential Item Functioning was undertaken in pooled data for each of the FIM motor and social-cognitive scales, respectively. RESULTS: Disordered thresholds were found on most items when using 7 categories. Fit to the Rasch model varied between countries. Differential Item Functioning was found by country for most items. Adequate fit to the Rasch model was achieved when items were treated as unique for each country and after a few country-specific items were removed. CONCLUSION: Clinical collected data from FIM for patients with stroke cannot be pooled in its raw form, or compared across countries. Comparisons can be made after adjusting for country-specific Differential Item Functioning, though the adjustments for Differential Item Functioning and rating scales may not generalize to other samples.

A force measuring treadmill in clinical gait analysis.

This preliminary study presents the development and testing of an instrumented treadmill device measuring the ground reaction forces (GRFs) and the feasibility of using this force measuring treadmill (FMT) in clinical gait analysis. A commercially available treadmill was modified and fitted out with three-dimensional strain-gauge force transducers. Tests of linearity, centre of pressure position (CoP), cross talk, natural frequency, background noises, and belt speed were undertaken in order to assess the performance of the FMT. In addition, the GRFs and segmental kinematics were recorded while healthy subjects and patients walked on the FMT, in order to compute the net ankle joint moments and the body centre of mass (CMb) kinematics and mechanics. The preliminary results of technical tests were satisfactory with an error less than 10% and dynamic tests in healthy subjects corresponded to the literature. The results of patients were clearly disturbed, demonstrating the ability of the FMT to discriminate pathological gaits from normal ones. We concluded that the GRFs measurements obtained from the FMT seem valid and the clinical assessment of net joint moments and CMb kinematics and mechanics seem feasible. The FMT could be useful device for clinical research and routine gait analysis since it allows gaining some extra room and quickly collecting the GRFs during a large number of successive gait cycles and over a wide range of steady-state gait speeds. However, more work is needed in this area in order to confirm the present results, collect reference data and validate the methodology across pathologies.

Outcome evaluation of the hand and wrist according to the International Classification of Functioning, Disability, and Health.

This article is a brief review of the outcome evaluation of the hand and wrist according to the International Classification of Functioning, Disability, and Health. Several tools currently exist to quantify outcome in hand surgery at the impairment level (eg, mobility, hand strength, cutaneous sensation, dexterity). According to the World Health Organization's paradigm, however, activity limitations and participation restrictions are also clinically relevant. The authors have recently built a measure of an upper limb-impaired individual's ability to manage manual activities in daily life. Participation and quality of life are difficult outcomes to measure because they are multidimensional and depend on such factors as functional abilities, general physical health, financial security, and stability of the social and familial environment.

Physical factors influencing pleasant touch during passive fingertip stimulation.

OBJECTIVE: Tactile explorations with the fingertips provide information regarding the physical properties of surfaces and their relative pleasantness. Previously, we performed an investigation in the active touch domain and linked several surface properties (i.e. frictional force fluctuations and net friction) with their pleasantness levels. The aim of the present study was to investigate physical factors being important for pleasantness perception during passive fingertip stimulation. Specifically we were interested to see whether factors, such as surfaces' topographies or their frictional characteristics could influence pleasantness. Furthermore, we ascertained how the stimulus pleasantness level was impacted by (i) the normal force of stimulus application (FN) and (ii) the stimulus temperature (TS). METHODS AND RESULTS: The right index fingertips of 22 blindfolded participants were stimulated using 27 different stimuli, which varied in average roughness (Ra) and TS. A 4-axis robot moved the stimuli horizontally under participants' fingertips with three levels of FN. The robot was equipped with force sensors, which recorded the FN and friction force (FT) during stimulation. Participants rated each stimulus according to a three-level pleasantness scale, as very pleasant (scored 0), pleasant (scored 1), or unpleasant (scored 2). These ordinal pleasantness ratings were logarithmically transformed into linear and unidimensional pleasantness measures with the Rasch model. Statistical analyses were conducted to investigate a possible link between the stimulus properties (i.e. Ra, FN, FT, and TS) and their respective pleasantness levels. Only the mean Ra and FT values were negatively correlated with pleasantness. No significant correlation was detected between FN or TS and pleasantness. CONCLUSION: Pleasantness perception, resulting from passive fingertip stimulation, seems to be influenced by the surfaces' average roughness levels and average FT occurring during fingertip stimulation.

Rasch-Built Measure of Pleasant Touch through Active Fingertip Exploration.

BACKGROUND: Evidence suggests that somatic sensation has a modality for pleasant touch. OBJECTIVE: To investigate pleasant touch at the fingertip level (i.e., glabrous skin site) through the elaboration of a linear unidimensional scale that measures (i) various materials according to the level of pleasantness they elicit through active fingertip explorations and (ii) subjects according to their pleasantness leniency levels. SUBJECTS: We enrolled 198 healthy subjects without any neurological disease. METHODS: Blindfolded subjects actively explored 48 materials with their index fingertips and reported the perceived pleasantness of each on a 4-level scale. The fingertip moisture levels on each subject were measured before the experimental session. Data were analyzed using the Rasch model. RESULTS: We elaborated unidimensional linear scale that included 37 materials according to their pleasantness of touch. The pleasantness level of 21 materials was perceived differently, depending on the fingertip moisture levels of the subjects. CONCLUSION: Based on our findings, we formulated a Pleasant Touch Scale. Fingertip moisture levels appeared to be a major factor for (un)pleasant feelings during active exploration.

Can manual ability be measured with a generic ABILHAND scale? A cross-sectional study conducted on six diagnostic groups.

OBJECTIVES: Several ABILHAND Rasch-built manual ability scales were previously developed for chronic stroke (CS), cerebral palsy (CP), rheumatoid arthritis (RA), systemic sclerosis (SSc) and neuromuscular disorders (NMD). The present study aimed to explore the applicability of a generic manual ability scale unbiased by diagnosis and to study the nature of manual ability across diagnoses. DESIGN: Cross-sectional study. SETTING: Outpatient clinic homes (CS, CP, RA), specialised centres (CP), reference centres (CP, NMD) and university hospitals (SSc). PARTICIPANTS: 762 patients from six diagnostic groups: 103 CS adults, 113 CP children, 112 RA adults, 156 SSc adults, 124 NMD children and 124 NMD adults. PRIMARY AND SECONDARY OUTCOME MEASURES: Manual ability as measured by the ABILHAND disease-specific questionnaires, diagnosis and nature (ie, uni-manual or bi-manual involvement and proximal or distal joints involvement) of the ABILHAND manual activities. RESULTS: The difficulties of most manual activities were diagnosis dependent. A principal component analysis highlighted that 57% of the variance in the item difficulty between diagnoses was explained by the symmetric or asymmetric nature of the disorders. A generic scale was constructed, from a metric point of view, with 11 items sharing a common difficulty among diagnoses and 41 items displaying a category-specific location (asymmetric: CS, CP; and symmetric: RA, SSc, NMD). This generic scale showed that CP and NMD children had significantly less manual ability than RA patients, who had significantly less manual ability than CS, SSc and NMD adults. However, the generic scale was less discriminative and responsive to small deficits than disease-specific instruments. CONCLUSIONS: Our finding that most of the manual item difficulties were disease-dependent emphasises the danger of using generic scales without prior investigation of item invariance across diagnostic groups. Nevertheless, a generic manual ability scale could be developed by adjusting and accounting for activities perceived differently in various disorders.

Validation of the ABILHAND questionnaire as a measure of manual ability in patients with rheumatoid arthritis.

OBJECTIVE: Hand and upper limb involvement is common in patients with rheumatoid arthritis (RA). However, its impact on manual activities of daily life has not been fully evaluated. A measure of manual ability was developed, through the Rasch measurement model, by adapting and validating the ABILHAND questionnaire, which measures the patient's perceived difficulty in performing everyday manual activities. METHODS: 112 patients with RA were evaluated. The following tests were performed: the ABILHAND questionnaire, the Health Assessment Questionnaire (HAQ), the Jamar grip and key pinch strength tests, the Box and Block dexterity test and the Purdue pegboard dexterity test. In total, 35 patients were reassessed to determine the test-retest reliability of the ABILHAND, and 6 patients were studied before and after therapy with tumour necrosis factor (TNF) blockers to address sensitivity to change. RESULTS: The Rasch refinement of the ABILHAND led to a selection of 27 items rated on a 3-point scale. The resulting ability scale was targeted to the ability of the patients. The item-difficulty hierarchy was stable across demographic and clinical subgroups and over time. Grip and key pinch strength and manual and digital dexterity on both hands were significantly, though moderately, correlated with the ABILHAND measures. Manual ability was also significantly related to the number of affected hands, disease duration, tender and swollen joint counts on upper limbs, disease activity and the HAQ. Sensitivity to change was demonstrated in patients treated with TNF blockers, commensurate with their clinical improvement. CONCLUSION: The ABILHAND questionnaire is a clinically valid person-centred measure of manual ability that could be useful in longitudinal RA studies.