Introduction
Patient-reported outcome measures (PROMs) are increasingly used in the assessment and management of musculoskeletal disorders [
1]. They have also become important primary outcome measures in research providing objective scores of patients’ level of self-perceived symptoms and/or disability [
1]. Many region-specific PROMs are available, including more than 30 for the shoulder region. These PROMs should be developed according to recommended guidelines and be tested for their measurement properties before they can be endorsed and used clinically and in research [
2,
3]. However, with varying degrees of compliance with stated development guidelines and the sheer number of PROMs available, shoulder clinicians can feel confused as to which PROM to use in individual circumstances.
The Disability of Arm, Shoulder, and Hand (DASH) [
1], the shorter version of the DASH (Quick-DASH) [
4] and the Shoulder Pain and Disability Index (SPADI) [
5] are among the most frequently used and recommended shoulder PROMs in both clinical and research fields with the measurement properties of each supported by good quality evidence [
3]. Previous studies have suggested that using two PROMs provides a more balanced measure of shoulder function [
6,
7]. These three PROMs are available in multiple languages [
3,
8] including recently published Nepali versions [
9‐
11]. They are the only available shoulder or upper limb specific tools in Nepali, the national language of Nepal.
Another PROM available in Nepali is the Patient-Specific Functional Scale (PSFS) developed to quantify activity limitations and physical function in any health condition and body part [
12,
13]. It is short and the patient chooses three to five of their own relevant activities to use as the assessment items. The English version of the PSFS has been validated in various health conditions including shoulder disorders and has been compared favourably to other musculoskeletal instruments resulting in it being a commonly used instrument in physiotherapy practice [
6,
13,
14]. A recent systematic review has endorsed the PSFS as a reliable, valid and responsive PROM for the assessment of physical function in shoulder disorder/pain [
15]. The PSFS has been validated for use in Nepali patients with general musculoskeletal pain with predominantly spinal and knee pain [
16] but its reliability, validity, and responsiveness properties have not been assessed in a shoulder pain population in Nepal. Additionally, no comparison has been made between the three Nepali shoulder PROMs and the PSFS. A comparison of these four PROMs would provide guidance for Nepali clinicians and researchers as to which PROM is the most suitable for use in patients with shoulder pain.
Therefore, the purposes of this study were to determine the measurement properties of the PSFS in Nepalese patients with shoulder pain and to compare the comprehensibility and measurement properties of the Nepali DASH, Quick-DASH, SPADI and PSFS instruments in order to provide a recommendation for use in clinical practice and research.
Material and methods
This multicentred longitudinal cohort study was approved by the Institutional Review Committee of Kathmandu University School of Medical Sciences, Nepal (Ref. No. 63/16) and was conducted over a six-month period from June to Dec 2016.
Patients and procedures
Patients receiving treatment from out-patient physiotherapy departments of three hospitals were screened by a physiotherapist for eligibility and volunteered for this study. These hospitals included a not-for-profit community-based hospital (Dhulikhel Hospital, Dhulikhel), a general urban hospital (Medicare Hospital, Kathmandu) and a large orthopaedic hospital (Nepal Orthopaedic Hospital, Kathmandu). To be included they had to be aged > 18 years, have adequate command of Nepali and have presented to the physiotherapy departments with the primary complaint of shoulder pain. Shoulder pain was defined as pain over the anterolateral, proximal aspect of the shoulder and/or upper arm, which was aggravated by shoulder movements. Patients were also required to test positive to one of the following: Hawkins–Kennedy test, Neer’s impingement test or resisted isometric manual muscle tests (abduction, external/internal rotation). Patients with cervical spine symptoms (pain on neck movements, pain in a dermatomal pattern and/or upper limb paraesthesia), pain of systemic or bioplastic origin were excluded from the study. Prior to the enrolment, all patients provided informed consent. Eligible patients completed the Nepali SPADI, DASH/Quick-DASH and the PSFS (as printed forms) at their first visit and again after an interval of 1–3 weeks. An interview method was used for illiterate patients with no prompting from the assessor. The Nepali version of the Global Rating of Change (GROC-NP) score was also included at the follow-up visit to categorise the patients into stable and improved groups.
Nepali outcome measures
The Nepali version of the DASH (DASH-NP) [
9] is a valid and reliable upper limb assessment tool consisting of 30 items. The Nepali Quick-DASH (QuickDASH-NP) [
10] is a subset of the DASH-NP that contains 11 items. Each item on both scales is assessed using a five-point Likert scale ranging from “No symptoms/difficulty” to “Worst symptoms/extreme difficulty”. The Nepali DASH has been reported to measure gross motor function, symptoms, fine motor tasks and recreational activities [
9] and the Nepali Quick-DASH symptoms and functions [
10]. If more than three items on the DASH-NP and one item on the QuickDASH-NP tools are missed, a valid calculation is not possible. Higher scores indicate higher intensity of the symptoms or disability and calculated using the formula:
$$\begin{gathered} {\text{DASH or Quick}} - {\text{DASH sum score }} = \, \left[ {\left( {{\text{sum of n responses }}/{\text{ n}}} \right) \, - { 1}} \right] \times {\text{25}} \hfill \\ \left( {\text{where n is equal to the number of completed responses}} \right). \hfill \\ \end{gathered}$$
The Nepali version of the SPADI (SPADI-NP) contains 13 items (five pain items and eight disability items) with patients rating their pain and disability symptoms on a numerical rating scale ranging from 0 (No pain/difficulty) to 10 (Extremely painful/difficulty) [
11]. The Nepali SPADI assesses symptoms under pain and disability constructs with acceptable measurement properties [
11]. More than two items left unanswered results in an invalid score. A higher score indicates greater disability and pain is calculated as
$${\text{SPADI score }} = \, \left( {{\text{total score }}/{13}0} \right){\text{ x 1}}00 \, = \, \%$$
The Nepali version of the PSFS (PSFS-NP) enables patients to identify and self-nominate three to five activities they are unable or have difficulty performing as a result of their health problems. The activities are rated on a scale of 0 (unable to perform) to 10 (Able to perform at prior level) [
12]. The scoring is in the reverse order of the SPADI, DASH and Quick-DASH, therefore, higher scores indicate less disability. A minimum of three functional activities is required to produce a valid calculation. PSFS score is calculated using the formula:
$${\text{PSFS score }} = {\text{ sum of activities score }}/{\text{number of activities}}$$
The GROC-NP uses a 7-point scale to measure change in patients’ overall health status. The middle indicator ‘4’ denotes “No change”, > 4 indicate progressive incremental improvements (5—small, 6—moderate, 7—large) and < 4 indicate worsening symptoms [
17]. Patients scoring GROC-4 were considered in the ‘stable group’ and GROC-5, 6 and 7 as ‘improved group’.
Study design
A two-stage study was conducted. The first stage included determination of measurement properties of the PSFS-NP in Nepali patients with shoulder pain and the second stage comparison between the measurement properties of the DASH-NP, QuickDASH-NP, SPADI-NP, and the PSFS-NP.
Stage one
Measurement properties analysis of the Nepali version of Patient-Specific Functional Scale (PSFS-NP)
The following measurement properties were tested for the PSFS-NP in accordance with the Consensus-based Standards for selection of health status Measurement INstruments (COSMIN) [
18] recommendations:
Reliability
(i)
Internal consistency—evaluated using Cronbach’s alpha (α) and was considered acceptable if α > 0.70 [
19].
(ii)
Test–retest reliability—confirmed using intraclass correlation coefficient (ICC 2, 1 agreement) with ICC > 0.70 ‘adequate’ in the stable group based on GROC categorisation [
20].
(iii)
Measurement errors—also called observational error including random and systematic errors, were estimated by the standard error of measurement (SEM) and smallest detectable change (SDC) using the following formulae:
(a)
SEM = standard deviation (pooled SD) multiplied by (1—ICC)1/2 and
(b)
SDC = z x √2 × SEM where z = 1.96 (z score is estimating a 95% confidence interval).
Validity
Construct validity of the PSFS-NP was assessed by hypothesis testing using Pearson’s correlations [
21]. Three
a-priori hypotheses were formulated:
The PSFS-NP would have a moderate to high negative correlation with the
These correlations would be negative as the PSFS-NP scores in the reverse order to the other three PROMs and moderate to high as previous research would suggest [
7,
15]). A correlation < -0.30 was considered weak, − 0.30 to − 0.70 moderate and > -0.70 high [
22]. Sufficient construct validity was determined if > 75% of the hypotheses were confirmed (i.e. all three hypotheses).
Responsiveness
An anchor-based method, Receiver Operating Characteristics (ROC) curve, using an external criterion (GROC-NP) was used to examine the responsiveness of the PSFS-NP. The ROC curve was plotted for the difference of PSFS-NP scores at baseline and follow-up administration between the stable group (GROC-NP score 4) and the improved groups (GROC-NP scores 5, 6, 7). The Area Under the Curve (AUC) > 0.70 was considered the cut-off value for sufficient responsiveness [
18].
Minimal Important Change (MIC) represents interpretability, and it was based on the optimal balance between sensitivity and specificity in the ROC curve.
Data were entered in an Excel spreadsheet [
23] and later transferred into SPSS version 24 [
24] for statistical analysis.
Stage two
Participant feedback
Feedback was acquired using a cognitive debriefing interview [
25] from the first five participants to assess the comprehensibility of the DASH-NP, QuickDASH-NP, and the SPADI-NP. Probing questions (in Nepali) were used in the interviews and included:
(i)
Did you find any difficulty while completing each instrument?
(ii)
Were the instructions and items easy to understand?
(iii)
Were all items relevant to your shoulder symptoms?
(iv)
Was the scoring method used in each instrument easy to answer? If not, why?
(v)
Did you leave any item blank? If yes, why?
Comparison between measurement properties of four instruments
The measurement properties of the DASH-NP, SPADI-NP and QuickDASH-NP have been reported previously and data extracted from the published manuscripts [
9‐
11]. The measurement properties of the PSFS-NP were obtained from the first stage of this current study.
Conclusion
There is strong measurement testing evidence to support the use of all four available Nepali instruments (PSFS-NP, SPADI-NP, DASH-NP, QuickDASH-NP) for shoulder pain patients in Nepal and there is no need to continue developing new PROMs or translating other shoulder-related PROMs into Nepali. The combined use of either the QuickDASH-NP or the SPADI-NP with the PSFS-NP would provide a comprehensive self-perceived assessment of Nepalese shoulder pain patients’ symptoms and be recommended for use in research settings and clinical management of shoulder pain in Nepal.
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