Linguistic validation, validity and reliability of the British English versions of the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire and QuickDASH in people with rheumatoid arthritis

Background Although the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire is widely used in the UK, no British English version is available. The aim of this study was to linguistically validate the DASH into British English and then test the reliability and validity of the British English DASH, (including the Work and Sport/Music DASH) and QuickDASH, in people with rheumatoid arthritis (RA). Methods The DASH was forward translated, reviewed by an expert panel and cognitive debriefing interviews undertaken with 31 people with RA. Content validity was evaluated using the ICF Core Set for RA. Participants with RA (n = 340) then completed the DASH, Health Assessment Questionnaire (HAQ), Short Form Health Survey v2 (SF36v2) and Measure of Activity Performance of the Hand (MAPHAND). We examined internal consistency and concurrent validity for the DASH, Work and Sport/Music DASH modules and QuickDASH. Participants repeated the DASH to assess test-retest reliability. Results Minor wording changes were made as required. The DASH addresses a quarter of Body Function and half of Activities and Participation codes in the ICF RA Core Set. Internal consistency for DASH scales were consistent with individual use (Cronbach’s alpha = 0.94–0.98). Concurrent validity was strong with the HAQ (rs = 0.69–0.91), SF36v2 Physical Function (rs = − 0.71 - − 0.85), Bodily Pain (rs = − 0.71 - − 0.74) scales and MAPHAND (rs = 0.71–0.93). Test-retest reliability was good (rs = 0.74–0.95). Conclusions British English versions of the DASH, QuickDASH and Work and Sport/Music modules are now available to evaluate upper limb disabilities in the UK. The DASH, QuickDASH, Work and Sport/Music modules are reliable and valid to use in clinical practice and research with British people with RA. Electronic supplementary material The online version of this article (10.1186/s12891-018-2032-8) contains supplementary material, which is available to authorized users.


Background
Rheumatoid arthritis (RA) impacts on hand and upper limb function. Within two years of diagnosis, 93% of people with RA report hand pain, 82% hand stiffness, 73% hand muscle weakness, 70% have at least one hand impairment and 50% experience shoulder joint tenderness and have reduced shoulder function [1][2][3]. Rehabilitation therefore includes maintaining and improving hand and upper limb function [4]. Using reliable, valid outcome measures is important to ensure problems are accurately identified and treatment benefits demonstrated.
The Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire is a widely used patient reported outcome measure (PROM) of upper limb function used in musculoskeletal conditions [5]. Its purpose is to detect upper limb disorders of differing severity, assess changes over time and evaluate outcomes of interventions [6]. It is one of the best upper limb measures clinimetrically [7,8]. The QUICKDASH, a shorter, more quickly administered version derived from the DASH, was developed using Rasch analysis [9][10][11]. Both also include optional modules for those whose jobs require a lot of upper limb performance (WORKDASH) and for sports people and musicians (sports and music: SPAMDASH).
The DASH was originally published in Canadian/ North American English. Outcome measures should be linguistically validated (i.e. translated and culturally adapted) into the language of the target country and psychometrically tested with target population(s) before being used in that country [12,13]. There are English versions of the DASH for Australia, Hong Kong and South Africa [14] but a British English version has not yet been linguistically validated and psychometrically tested in the United Kingdom (UK). Currently, the Canadian/North American English version is being used in rheumatology clinical practice and research. Whilst much of the North American English DASH is understandable to British English speakers, clinicians and patients regularly comment that some activities included are: unclear, e.g. "yard work"; not in common usage e.g. "transportation"; infrequently performed in the UK, e.g. "wash walls." Additionally, some phrases and sentences could be shortened to reflect Plain English usage. Consequently, a British English version is required that is then psychometrically tested in populations it is commonly used with.
The DASH consists of 30 items evaluating upper limbrelated activities, participation and symptoms [11]. There has been some debate as to whether the DASH is unidimensional. Factor analysis of the original Canadian/North American [11] and also Dutch [15], Japanese [16] and Chinese [17] versions of the DASH identified a single factor and thus all items can be summed to form a total score. However, studies using factor and /or Rasch analysis with the Canadian/North American DASH in the UK identified two factors [18] while the French [19], Italian [20] and Canadian /North American [21] versions revealed three factors. Psychometric testing of measures should include a combination of classical testing and item response theory (e.g. Rasch analysis) to establish psychometric properties, including unidimensionality [22].
The overall aims of this study were to: linguistically validate the DASH into British English; investigate content validity of the DASH in RA; and evaluate the psychometrics of the British English DASH and QuickDASH amongst people with RA in the UK. The psychometrics assessed were: concurrent and discriminant validity, internal consistency, test retest reliability, sensitivity to change, compliance (amount of missing data) and floor and ceiling effects of the British English DASH and Quick-DASH amongst British people with RA.
Alongside this, we also investigated construct validity of the British English DASH and QuickDASH using Rasch analysis. This is reported separately [Prodinger B, Hammond A, Tennant A, Prior Y, Tyson S. Deconstructing the Disabilities of the Arm, Shoulder and Hand (DASH) and QuickDASH in Rheumatoid Arthritis, submitted].

Methods
Ethical approval was obtained from the National Research Ethics Service Committee North West -Greater Manchester North (12/NW/0841) and the University of Salford's School of Health Sciences Ethics Panel. All participants provided written, informed consent.

Participants
Participants were recruited: by research nurses screening for eligibility in 17 Rheumatology out-patient clinics (either in clinic or identified from departmental databases); and from amongst participants in a previous outcome measure study we conducted, who had consented to be contacted for future studies. All were recruited from the same Rheumatology out-patient clinics originally and with whom eligibility was re-checked prior to consent. Participants were eligible if they: had a confirmed diagnosis of RA; were able to read, write and understand English; and had not (or were not about to) altered their disease-modifying medication regimen in the last three months (which could affect test-retest reliability).

Linguistic and cross-cultural validation
The adaptation procedures devised by the Institute of Work and Health for DASH translation were followed [23]. This consists of six steps: (1) forward translation: two translators (AH: a rheumatology rehabilitation researcher familiar with the DASH) and a non-health professional unfamiliar with the DASH (JG: an experienced teacher) independently reviewed the DASH to identify any words that needed to be changed into British English (e.g. transportation is termed transport) and use of Plain English (i.e. simplifying words and phrases). (2) translation synthesis: an independent recorder assisted the two translators agreeing any recommended changes (3) backward translation: was not required as the translation was into another form of English. (4) expert committee review: The committee included: the two translators (AH, JG); synthesis recorder (YP); an experienced Rheumatology occupational therapist familiar with using the DASH (AJ); an English language expert (GMcL); a Canadian English-speaking researcher (KH); and an experienced outcome measures researcher (ST After each of steps 4, 5 and 6 reports were sent to the Institute of Work and Health for translation approval before proceeding to the next step [23].

Psychometric testing procedures
Participants were mailed a questionnaire booklet which collected data to describe the recruited population: demographic and disease data: age, gender, marital, educational and employment status, disease duration and RA diseasemodifying medication as well as the measures described below. Two to three weeks later, participants were mailed the British English DASH to complete at home a second time (to evaluate test-retest reliability). Two reminders were sent for each mailing, as necessary.

Measurement instruments
The British English DASH The DASH consists of 30 items, measured using fivepoint Likert scales (1-5): 21 regarding daily activity; five regarding symptoms; three about participation (the impact of the condition on daily life); and one about confidence in abilities [28]. The QUICKDASH was derived from the DASH and consists of 11 items (six of daily activity ability; two about symptoms (pain and tingling); and three about participation) [11]. The two optional modules (SPAMand WORK-DASH) were also included.
The medical outcomes survey 36 item short-from health survey version 2 (SF36v2) From which sub-scales of Physical Function, Bodily Pain and Vitality (fatigue) scales were selected [29,30]. Qual-ityMetric Health Outcomes™ Scoring Software 4.5 was used to manage missing SF36v2 data and calculate norm-based scores converted to 0-100 scale for each sub-scale [31]. Lower scores denote worse health states.

The health assessment questionnaire (HAQ)
Indicates ability to perform 20 daily activities rated on a 0-3 scale (0 = not at all difficult; 3 = unable to do) [32], scored using the HAQ20 method, in which the total score is obtained by summing all 20 items (0-20 = mild; 21-40 = moderate; 41-60 = severe disability) [33,34]. This method was used as the HAQ20 does not weight items worse if an assistive device is used, as occurs when normally scoring the HAQ. Higher scores denote greater activity limitations.

The hand HAQ
Seven items of upper limb function derived from the HAQ (i.e. Dressing; Cutting meat/food; Lifting a full cup or glass; Opening a new milk carton; Opening car doors; Opening jars which have been previously opened; Turning taps on and off [35]. The score is the sum of the seven items, with higher scores denoting greater activity limitations. The British English measure of activity performance of the hand (MAP-HAND) Eighteen items of activity ability requiring hand use, each measured on a 0-3 scale (0 = not at all difficult; 3 = unable to do) [36,37]. The total score is obtained by summing the 18 items, with higher scores denoting greater activity limitations.

Symptom 10-point numeric rating scales (NRS)
Evaluating: hand pain on activity; and self-reported disease activity level, general pain at rest, general pain on movement, stiffness, movement limitations, from the Evaluation of Daily Activity Questionnaire [38].

RA quality of life scale (RAQOL)
Thirty items about quality of life (QoL) answered yes (=1) or no (=0), with yes items summed to give a total score. Higher scores indicate worse QoL [39].

Perceived change in health status
At Test 2 only, this was measured using a 5-point NRS by asking "Overall, how much is your arthritis troubling you now compared to when you last completed this questionnaire?" (1 = much less; 2 = somewhat less; 3 = about the same; 4 = somewhat more; 5 = much more).
We hypothesised that there would be strong correlations between the four DASH scales and these measures.

Sample size
As Rasch analysis was also being used to assess construct validity of the British English DASH, a sample size of at least 250 was recruited [Prodinger B, Hammond A, Tennant A, Prior Y, Tyson S. Deconstructing the Disabilities of the Arm, Shoulder and Hand (DASH) and QuickDASH in Rheumatoid Arthritis, submitted]. This number was determined from the need to ensure a uniform distribution of patients across the construct of upper limb function, so that the precision of the estimate of both persons and items, across the construct, remains similar [40]. At least 79 sets of repeated responses were required to demonstrate that a test-retest correlation of 0.7 differs from a background correlation (constant) of 0.45, with 90% power at the 1% significance level. A test-retest correlation of 0.7 is deemed a minimum acceptable level [41].

Statistical analyses
Rasch analyses of both the DASH and QUICKDASH indicated that, using a testlet approach taking account of local dependency, both can be considered as unidimensional and total raw scores, standardised to 0-100, can therefore be used [ For both the DASH and QUICKDASH, standardised (0-100) scores are calculated by: (where n is the number of completed responses). A higher score represents worse ability/symptoms. The DASH score cannot be calculated if there are more than three missing items, nor the QUICKDASH if more than one missing item.
The WORK-and SPAM-DASH were scored by: adding the assigned values for each response, dividing by 4 (number of items); subtracting 1; and multiplying by 25 to convert to a 0-100 scale. Optional module scores cannot be calculated if there are missing items.
The Statistical Package for the Social Sciences v20 was used for analyses [42], apart from linear weighted kappas, calculated using MedCalc [43]. As all measures consist of ordinal data, non-parametric statistical tests were used to assess the psychometrics.

Discriminant validity
Was assessed using Kruskal-Wallis tests to evaluate differences in scores between participants with different degrees of disease activity, using the disease activity NRS (low disease activity = 0-3; moderate = 4-6; high = 7-10).

Internal consistency
Was assessed using Cronbach's alpha. Results of ≥0.8 were deemed good to excellent [44]. A value of ≥0.85 is consistent with individual use and > 0.7 with group-level use.

Sensitivity to change
Was assessed by calculating Standard Error of Measurement (SEM) and the Minimal Detectable Change 95 (MDC 95 ) scores, i.e. a statistical estimate of the smallest detectable change corresponding to change in ability [47,48].
The formulae used were: SEM = s √ (1r), where s = the mean and standard deviation (SD) of Test 1 and Test 2 (retest), r = the reliability coefficient for the test, i.e. Pearson's correlation co-efficient between Test and Test 2 values. Thereafter the MDC 95 was calculated using the formula: MDC 95 = SEM × √ 2 × 1.96 [48].

Compliance (missing data)
The number of missing data items were reviewed to identify the percentage of the four DASH scales which could not be scored, and the commonest missing items.

Floor and ceiling effects
Were considered present if > 15% of participants achieved either the lowest or highest scores in the four DASH scales [49,50].

Steps 1 to 5: Linguistic validation and cross-cultural adaptation
The expert panel agreed several changes to simplify language: "perform" was changed to "do"; "estimate" to "guess"; "household chores" to "household jobs"; "wash floors" to "clean floors"; "put on a pullover sweater" to "put on a jumper"; "transportation" to "transport"; "using your usual technique for your work" to "doing your work in your usual way"; "using your usual technique for playing your instrument or sport" to "playing your instrument or sport in your usual way"; "yard work" to "outdoor property work" (as this was identified as meaning outdoor property maintenance in Canada); "wash walls" to "wash windows" (as the former is a rare activity and washing windows requires a similar action); and for "carry a heavy object (over 10lbs)" we added "or 5 kg" to provide a rough metric equivalent.
Cognitive debriefing interviews were conducted with 26 women and five men (see Table 1). Minor changes to clarify were suggested for seven items. Five participants were unsure whether the instruction "ability to do the following activities…" referred to ability with or without aids and adaptations, as they might answer differently using these. The panel agreed not to change instructions as these are consistent across all language versions of the DASH. For the activity items, only two raised interpretation concerns. Five interpreted "Make a bed" (item 9) as completely changing the bed linen. In British English, "make a bed" describes the daily tidying or straightening bedding and was interpreted as such by other participants. Discussion with Canadians indicated that this means the same in Canadian/North American English. Nine queried whether "manage transport needs" (item 20) referred specifically to driving, getting a lift or using public transport, as each required different levels of upper limb activity, or to multiple transport methods. Other participants interpreted this related to their own travel circumstances. For symptom severity, eight participants indicated it was difficult differentiating between "arm, shoulder or hand pain severity" (item 24), and pain severity "when you do any specific activity" (item 25) as their pain usually lasts some time without changing with different activities. However, the other participants could identify activities inducing/ exacerbating pain and thus rate these items separately. Five were unable to identify whether the "weakness in their arms, shoulder or hand" (item 27) was any different in the last week than usual, as their upper limb was constantly weak. Thirteen were unsure if they could solely attribute sleeping problems to arm, shoulder or hand pain (item 29) as they either had multiple painful joints or widespread pain, although they did answer the question. The panel discussed these items and decided not to make further changes. The Flesch Reading Ease score for the British English DASH was 62.8, i.e. similar to the Canadian DASH (61.5), indicating a reading age of 13 to 15-year olds is required [51].  Table S1).
Step 6: Psychometric testing Participants Overall, 595 people were screened for eligibility, 423 consented and 340 returned the Test 1 questionnaire booklet and 273 the Test 2 booklet (see Fig. 1). Participant characteristics are shown in Table 1 and health status, activity limitations and quality of life measures descriptive data are shown in Table 2. The mean time between tests was 34.6 (SD 13.07) days.

Discriminant validity
There were significant differences between the three levels of perceived disease activity for the DASH, Quick-DASH, WORKDASH and SPAMDASH, with  Table 4).

Internal consistency
Cronbach's alpha values for the four DASH scales were excellent ranging from 0.94 (WORKDASH) to 0.98 (DASH) (see Table 5).

Test-retest reliability
Data for those participants reporting they were "the same" at Test 2 as at Test 1 were analysed. For all four DASH measures, correlations between Test 1 and Test 2 scores were strong (r s = 0.74-0.95). For the DASH and QuickDASH, ICC(2,1) were excellent (see Table 5). As there are no Rasch transformation tables available for the WORK-and SPAMDASH, ICC(2,1) could not be calculated. For individual items in the DASH and QuickDASH, reliability was moderate (n = 9) or good (n = 21); for the WORKDASH moderate (n = 3) and good (n = 1); and SPAMDASH for all four items were good.

Floor and ceiling effects
There were no floor or ceiling effects for the DASH (2% scored 0; 0.3% scored 100) or the QuickDASH (5.6% scored 0, 0% scored 100). However, for the WORK-and SPAM-DASH there were floor effects: 21 and 17.5% respectively. There were no ceiling effects for the WORK-DASH (2%) but there were for the SPAMDASH (15.8%).

Discussion
Linguistically validated British English versions of the DASH and QuickDASH are now available for use in the UK. These British-English translations demonstrated good psychometric properties in a sample of people with RA and can be used in both clinical practice and research. We ensured linguistic and cross-cultural validity of the DASH by using the IWH DASH translation process, while gaining the developers' approval throughout. During cognitive debriefing, some participants were unsure if "ability to do the following activities…" referred to ability with or without aids and adaptations, as ability can differ when using these. Clarifying this, to ensure respondents answer in the same way, could be beneficial. However, the 50 language versions currently available do not specify this, so these changes were not made.
In terms of content validity, the DASH scales address some of the Body Functions and over half of the Activities and Participation items in the Brief ICF Core Set for RA and those not covered by the DASH are mostly those not relevant to the arm, shoulder and hand. Some core issues are potentially relevant and not reflected in the DASH. These include: body image (1801), as many people can be disturbed by their hand appearance in RA [52]; muscle endurance (b740) and maintaining a body position (d415), as DASH ICF linking did not specifically identify prolonged and/or static actions [27]; and using communication devices and techniques (d360), as the use of smart/mobile phones and computers/tablets is now ubiquitous, compared to when the DASH was developed in 1995. However, participants did not raise such issues in the cognitive debriefing interviews suggesting the DASH adequately reflects their main problems. As device use is a common source of upper limb pain in those with high-frequency use, it may be time to update the DASH and include this as a new item, thus reflecting modern-day life. Potentially, it could replace an existing item which is now less common, e.g. change a lightbulb overhead, as the advent of LED bulbs means this activity is now less frequently performed.