|Year : 2022 | Volume
| Issue : 1 | Page : 9-15
Arabic version of the anterior cruciate ligament return to sport index: Translation and cross-cultural adaptation
Husam Almalki1, Lee Herrington2, Richard Jones2
1 Department of Rehabilitation, King Abdulaziz Specialist Hospital, Taif, Saudi Arabia
2 School of Health and Society, University of Salford, Salford, UK
|Date of Submission||20-Oct-2021|
|Date of Acceptance||06-Dec-2021|
|Date of Web Publication||4-Apr-2022|
Department of Rehabilitation, King Abdulaziz Specialist Hospital, Taif 26513
Source of Support: None, Conflict of Interest: None
Purpose: Several factors influence the decision to return to sport (RTS) after anterior cruciate ligament reconstruction (ACLR). The literature revealed a link between psychological factors and RTS rates following ACL injury. The anterior cruciate ligament return to sport index (ACL-RSI) scale was created to assess the psychological impact of an ACL injury. A rigorous process of cross-cultural adaptation and validation is required to achieve equivalence between the original publication and the target version of the scale to administer the ACL-RSI to Arabic speakers. The purpose of this research is to translate and culturally adapt (ACL-RSI) for Arabic people who have ACLR.
Materials and Methods: Translation and backward translation of the English version of the ACL-RSI were performed in accordance with the guidelines for cross-cultural adaptation. Following translation, 105 ACLR patients were recruited to complete Arabic version of RAND-36-item health survey, Arabic version of the knee injury and osteoarthritis outcome score and visual analog scales, along with the Arabic (ACL-RSI) scale. We looked at test–retest reliability, internal consistency, construct validity, and content validity.
Results: The internal consistency was excellent (Cronbach's = 0.94). The test–retest reliability was high, with an intraclass correlation coefficient (ICC) of 0.92 and a standard error of measurement of 4.41. There was a good construct validity with no floor or ceiling effects, as well as good convergent and divergent validity.
Conclusions: This study confirmed that the Arabic (ACL-RSI) scale has good measurement properties, demonstrated that this instrument is an excellent tool to evaluate psychological factors for Arabic patients with ACLR.
Keywords: Anterior cruciate ligament reconstruction, anterior cruciate ligament return to sport index, return to sports
|How to cite this article:|
Almalki H, Herrington L, Jones R. Arabic version of the anterior cruciate ligament return to sport index: Translation and cross-cultural adaptation. Saudi J Sports Med 2022;22:9-15
|How to cite this URL:|
Almalki H, Herrington L, Jones R. Arabic version of the anterior cruciate ligament return to sport index: Translation and cross-cultural adaptation. Saudi J Sports Med [serial online] 2022 [cited 2022 Nov 30];22:9-15. Available from: https://www.sjosm.org/text.asp?2022/22/1/9/342526
| Introduction|| |
Following several factors, including physical, psychological, and demographic factors, play a role in the decision to return to sport (RTS) after anterior cruciate ligament reconstruction (ACLR). Previously, physical performance tests were used to assess side-to-side differences, with the clinical focus being whether the patient can achieve a score of 85% or higher on the limb symmetry index. Although a meta-analysis found that approximately 90% of patients who underwent ACLR were successful in their physical performance assessments, despite the fact that only 64% of patients were able to RTS. This disparity between the low rate of RTS and good physical performance outcomes following ACLR may be due to psychological factors.
Ardern et al. discovered a link between psychological factors and RTS rates following anterior cruciate ligament (ACL) injury. Fear of re-injury has been shown to be a challenging and present psychological factor following an ACL injury. According to Kvist et al., nearly 24% of the ACLR patients did not RTS because they were afraid of re-injury. the ACL Return to Sports after Injury (ACL-RSI) scale was developed and validated, which contains 12 factors or domains that evaluate emotions, confidence in performance, and risk appraisal in relation to RTS after ACL injury and/or surgery. This scale was originally written in English and has been translated and validated in populations with ACLR patients from Sweden, France, China, Turkey, Netherland, Brazil, Korea, Lithuania, Japan, and Spain,,,,,,,,,, respectively.
In addition, the (ACL-RSI) has been shown to have an ability to identify which patients RTS, and those who do not RTS, following ACLR., found the (ACL-RSI) scale to be the best predictive parameter for RTS at six months post ACLR. As a result, it is expected that an Arabic version of the ACL-RSI scale would be highly beneficial for assessing the influence of psychological factors on RTS in Arabic patients with ACLR.
A thorough process of cross-cultural adaptation and validation is required for any scale to be used with Arabic speakers so that equivalence between the original scale and the target version of the scale can be achieved. An important consideration in this process is the process of evaluating such instrument across cultures because even if items are well translated, it must be culturally appropriate.
This study was ethically approved by the University of Salford's Research, Innovation, and Academic Engagement Ethical Approval Panel (HSCR 1617-43). Each participant in this study received a written information sheet with detailed study information and informs them of their right to withdraw. All information gathered from subjects was stored on a secure, password-protected computer. Each subject was assigned a reference number to ensure that no personal information could be gleaned from the data (Data Protection Act, 1998).
| Materials and Methods|| |
Translation and cross-cultural adaptation
The translation and cross-cultural adaptation process followed the previously established guidelines. Three Arabic native speakers have translated the English (ACL-RSI) scale into Arabic (an orthopedic surgeon, a physical therapist, and a professional translator). Three native English speakers back translated the Arabic translations to English (two English teachers and a professional English translator); they had no prior knowledge of the original version. The translated scale was checked and discussed by a multidisciplinary committee of two orthopedic surgeons, a psychologist, a physiotherapist, and a professional translator, all of whom are bilingual.
The committee reviewed the Arabic (ACL-RSI) and reached an agreement on any incongruity, resulting in the translation of the scale, with translation in a language that understood by a 12-year-old child. When the translation was presented to the committee, they investigated items, instructions, response options, and scoring.
Pilot study of the prefinal version
The Arabic (ACL-RSI) prefinal version was tested on 35 Arabic-speaking patients who had undergone ACL reconstruction. This was done to ensure that they fully comprehended all aspects of the scale and completed it satisfactorily. Any issues that arose during the administration of the (ACL-RSI) scale were noted, and at the end of the interview, each patient was asked to comment on the scale and point out any words that they had difficulty understanding. This ensured that the scale was easy to understand. All the subjects declared to understand all of the questions and answer choices. Therefore, this version was not modified further and was considered the final version.
Based on the pilot results, a committee meeting was scheduled to approve the Arabic (ACL-RSI) scale (See the supplementary data). Cross-cultural adaptation necessitated not only translation but also the modification of cultural terms, idioms, and colloquialisms. As a result, some minor changes were made for some items to keep the original concept's meaning, and some easily understandable, simple formal Arabic language with colloquial idioms was used to make the items more understandable.
We obtained a sample of 105 Saudi ACLR patients between the ages of 18 and 44 with an unilateral ACL injury and completed their rehabilitation programs after ACLR. All the patients are speaking Arabic as a first language with a good education, which ensures that they understand and can accurately response to the questions. Patients with heart, respiratory, or neurological issues that restrict general health; any problems influence the lower extremity; and people with mental disorders were all excluded.
Participants were recruited through rehabilitation departments in Saudi Arabia. Patients were given invitation letters along with the participant information sheet and data access form. The forms were returned by individuals during their regular hospital appointments. The participants were evaluated to determine their eligibility, then they were briefed on the study and any questions they had were fully answered.
After agreeing to participate in the study, the participants were given a package of patient-reported outcome measures (PROMs) known as an instrument package that included the patient's characteristics, the RAND-36-item health survey (RAND-36), the knee injury and osteoarthritis outcome score (KOOS), and the visual analog scales (VAS), along with the (ACL-RSI) scale, the participants were asked to complete the instrument package independently during their regular visits to the hospital.
The ACL-RSI is a condition-specific scale with a 12-item scale for measuring three psychological constructs on a scale of 0 to 100: confidence in performance, emotions, and risk appraisal. A higher score indicates a more favorable attitude toward RTS.
The Arabic (KOOS) consists of 42 items divided into five subscales: pain, symptoms, activities of daily living (ADL), sport and recreation (Sport/Rec), and knee-related quality of life (QoL). Each item was scored using a five-point Likert scale ranging from 0 (extreme problems) to 4 (no problems), each subscale was calculated separately on a scale of 0–100 (0 = bad knee functions, 100 = normal knee functions).
The Arabic version of the (RAND-36) divided into eight subscales: physical functioning, role limitations due to physical problems, role limitations due to emotional problems, vitality, emotional well-being, social functioning, pain, and general health. These subscales are scored on a scale of 0–100, with low scores indicating bad health.
The (VAS) numeric pain scale ranges from 0 (no problem) to 10 (extreme problem), and this was used to assess the average intensity of overall knee pain felt during the previous week of recruitment. VAS is a reliable and valid tool for assessing patients with knee problem. VAS scored on a scale of 0 to 100. A higher score indicates a more pain.
Psychometric scale properties and data analysis
The percentage of refusals, completed scale, and missing items, as well as the time required to complete the scale, were used to assess the acceptability. Furthermore, the acceptability of the scale was considered by noting the percentage of items, confusing items, and the subjects' willingness to complete the scale a second time.
Cronbach's alpha was used to calculate the internal consistency for the first administration, and a value of 0.70 or higher was considered acceptable., The (ACL-RSI) scale, the KOOS, the RAND-36, and the VAS were completed by the ACLR patients, and the test-retest reliability was assessed during the 14-day follow-up appointment to complete it. The patients were asked to complete the ACL-RSI scale after 2 weeks to evaluate the test-retest reliability. To decrease the possibility of memorization, all instruments were combined into an instrument package. The duration of evaluating the test-retest reliability needs to be not too long to void remarkable changes in subjects' status that may affect their answers but not too short to reduce questions memorization. A 2-week period is commonly deemed adequate for PROMs evaluation. The ACL-RSI scale was completed by all the participants (n = 105) within the allocated time. To assess test-retest stability, the intra-class coefficient correlation (ICC) was used, and an ICC of 0.7 or higher was considered acceptable.,,
Standard error of measurement (SEM) is the systematic and random error in a patient's score that is not due to real changes in the scores. SEM for absolute agreement was obtained using the formula SEM = SD (1-ICC).
The Spearman correlation coefficient (r) was used to examine the construct validity, which measured the scale's capability of measuring what it was intended to measure. As evidence of construct validity, a priori hypothesized that patterns of relationships with other scales are needed. As a result, construct validity was assessed by investigating the relationships between the ACL-RSI scale to the KOOS subscales, RAND-36 subscales, and VAS. The construct validity of the (ACL-RSI) considered acceptable if 75% of the hypotheses were approved. It was hypothesized that:
- There would be a strong correlation between ACL-RSI and KOOS QoL
- There would be stronger correlations between the ACL-RSI scale and RAND-36 Mental Health subscales than between the ACL-RSI scale and RAND-36 Physical Health subscales
- There would be moderate to a strong negative correlation between (ACL-RSI) and VAS.
According to Terwee et al., good content validity is accompanied by the absence of floor/ceiling effects, which means that no missing items are at the margins of the scale. The floor/ceiling effect is a limitation shown when measuring PROMs. It is critical to be aware of floor/ceiling effects, and any results with such limitations should be used with caution. The floor/ceiling effects existed when 15% of participants scored the maximum or minimum possible score on the instrument.
IBM SPSS software was used for the statistical analyses (version 24, SPSS Inc., Chicago, IL). To present the data descriptively, descriptive statistics (mean, range of scores, and standard deviations) and scatter graphs were used. Cronbach's alpha was used to determine the internal consistency, ICC was used to determine the reliability, and the SEM was used to determine the level of agreement. According to Coppieters et al., ICC was classified as excellent more than (0.90), good (0.70–0s. 90), fair (0.40–0.70), and poor less than (0.40). Therefore, poor ICC with score less than 0.40 being rejected. While the ICC appears straightforward with regard to obtaining data, it cannot depict reliability properly if it is used on its own because no error margin is set out between two measurements. Calculation of the SEM can help greatly in discerning the actual change in outcomes, instead of a measurement error. Having a high ICC and a low SEM is considered reliable.
Relationships were tested to evaluate the validity by using Spearman's rank correlation (p), to evaluate the relationships between (ACL-RSI) scale and the KOOS, RAND-36, and VAS. Spearman correlations were defined as weak correlation less than 0.30; moderate correlation (0.30–0.60); strong correlation r more than 0.60. P value was set at 0.05.
| Results|| |
The study included 105 ACLR male patients with a mean (SD) age of 30.34 years (5.9); a weight of 78.08 kg (16.42); a height of 174 cm (7.2); and a body mass index of 25.8 (1.9). All subjects participated in sports on a regular basis. Sixty-six subjects (63%) have had a right knee injury, while 39 subjects (37%) have had left knee injury. Meniscus with ACL injuries was present in 66 subjects (63%). Seventy-five subjects (71%) have had ACL reconstruction with hamstring tendon grafts, while only 30 subjects (29%) have had patellar tendon grafts. The mechanism of ACL injury was noncontact in 57 subjects (54%) and due to a physical contact in 48 subjects (46%). Ninety-six subjects have had ACL injury while playing football. The average wait time for ACL patients before surgery was 6.9 months. The average period for postoperative rehabilitation was 5.4 months, ranging from 5 to 6 months.
Acceptability of the Arabic anterior cruciate ligament-return to sport index
The scale was completed by all of the subjects, no missing items were found, indicating that the acceptability was good for the (ACL-RSI) scale. The scale took about 5 min to complete, all the items were very clear and not confusing. The scale was completed and returned again by all the participants after 2 weeks.
[Table 1] shows the ACL-RSI scale's, Cronbach's alpha, ICC, SEM, and Smallest Detectable Difference (SDD), which were 0.94, 0.92. 4.42 points and 12.22 points, respectively, demonstrating excellent internal consistency and test-retest reliability.
|Table 1: Descriptive data of anterior cruciate ligament-return to sport index scores, floor/ceiling effects, Cronbach's alpha, intraclass correlation coefficient, standard error of measurement, and smallest detectable change|
Click here to view
[Table 2] shows Spearman's correlation between the Arabic (ACL-RSI) scale with other scales. A priori hypothesized that patterns of relationships with other scales were approved. There was a moderate relationship between ACL-RSI scale and KOOS subscales and VAS (P = 0.39), (P = 0.41), respectively. A strong relationship was found between ACL-RSI scale and RAND-36 mental health subscales (P = −0.41).
|Table 2: Relationship between the Arabic (anterior cruciate ligament-return to sport index) scale and other instruments|
Click here to view
Because just six participants (5.71%) recorded the maximum possible score on the (ACL-RSI), floor/ceiling effects are thought to be absent in the Arabic (ACL-RSI), as this percentage is <15% of all participants.
| Discussion|| |
For measuring outcomes after ACL injuries, an Arabic version of the (ACL-RSI) scale is required. To date, there is no Arabic version of ACL-RSI scale. Thus, this study aimed to translate and culturally adapt the ACL-RSI scale into Arabic. The translated version's psychometric properties have been evaluated and found to be satisfactory. This study included extensive testing for reliability and validity, which revealed that the scale should be beneficial for research and clinical practice and provide accurate scores.
The Arabic version of the ACL-RSI scale was extremely acceptable because all items were clear and not confusing and no missing items were found; and the subjects took a relatively short time to complete it. All of this demonstrates that the translation is acceptable and can be used with patients after ACL injuries.
The Arabic (ACL-RSI) has shown strong consistency. The Cronbach's alpha (0.94) was shown to be on par with the Cronbach's alpha of the Swedish (0.95); the French (0.96); the Chinese (0.96); the Dutch (0.94); the Korean (0.93); the Lithuanian (0.94); the Japanese (0.91); and the Spanish (ACL-RSI) version (0.90),,,,,,,, respectively. Furthermore, the test-retest reliability of the Arabic (ACL-RSI) in this study was high (ICC = 0.92), and this is similar to the French (ICC = 0.90); the Turkish (ICC = 0.92); the Dutch (ICC = 0.93); the Korean (ICC = 0.95); the Lithuanian (ICC = 0.92); the Japanese (ICC = 0.95); and the Spanish (ACL-RSI) version (ICC = 0.90).,,,,,,
In the current study, construct validity has been assessed by examining the correlation between the Arabic (ACL-RSI) with, RAND-36, KOOS subscales, and VAS. The relationship between the Arabic (ACL-RSI) and RAND-36 subscales of Mental Health was high, as following: role limitation due to emotional problems (r = 0.66), vitality (r = 0.75), emotional well-being (r = 0.62). This was expected, as the ACL-RSI scale considers psychological readiness among patients. Determining the specific relationship of the ACL-RSI scale with the KOOS subscales has been examined to check its validity. Previous studies have also reported high correlations between ACL-RSI scale and the KOOS QoL subscale that are similar to the present study (r = 0.55), for example the French version (r = 0.64); the Chinese version (r = 0.66), the Korean version (r = 0.68), the Turkish version (r = 0.58), and the Spanish version (r = 0.60),,,,, respectively. On the other hand, other KOOS subscales (pain, symptoms, ADL, and sport and recreation) showed lower correlations with the Arabic (ACL-RSI) than in previous studies. The KOOS is intended for use with patients suffering from knee injuries that could result in posttraumatic osteoarthritis. These differences could be because of the time elapsed (TE) following ACLR. TE after ACLR was 5.4 months in the current study, whereas it was 42 months in the Swedish version; 13.6 months in the Turkish version; and 9.5 months in the Dutch version. Due to the TE being longer in the previous studies, the patients' knee function and RTSs readiness could have been better, which may have resulted in a stronger relationship between the KOOS subscales and the ACL-RSI scale. In normal clinical application, the Arabic (ACL-RSI) could assist clinicians by providing them with standardized and reliable instrument for identifying ACLR individuals who may it difficult to RTS due to psychological factors. The evaluation of psychological factors is a key to supporting patients and spotting who require psychological interventions in conjunction with physical therapy.
This study has some limitations in terms of cross-cultural adaptation, internal consistency, the test-retest, and validity. As previously stated, the participants were all male, so the findings cannot be generalized for female ACLR patients, though no previous studies found differences between male and female in psychological factors following ACLR. Moreover, only ACLR patients were in the inclusion criteria. As a result, more research is needed to examine the generalizability of the Arabic (ACL-RSI) to patients suffering from ACL deficiency (ACLD).
| Conclusions|| |
This study demonstrated that the Arabic (ACL-RSI) scale is a valid and reliable scale for Arabic population with ACLR, though more studies with a further diverse sample are needed to allow generalization to a larger population including female and ACLD patients.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| Supplementary Data|| |
| References|| |
Lentz TA, Zeppieri G Jr., Tillman SM, Indelicato PA, Moser MW, George SZ, et al
. Return to preinjury sports participation following anterior cruciate ligament reconstruction: Contributions of demographic, knee impairment, and self-report measures. J Orthop Sports Phys Ther 2012;42:893-901.
Barber-Westin SD, Noyes FR. Factors used to determine return to unrestricted sports activities after anterior cruciate ligament reconstruction. Arthroscopy 2011;27:1697-705.
Ardern CL, Taylor NF, Feller JA, Whitehead TS, Webster KE. Psychological responses matter in returning to preinjury level of sport after anterior cruciate ligament reconstruction surgery. Am J Sports Med 2013;41:1549-58.
Everhart JS, Best TM, Flanigan DC. Psychological predictors of anterior cruciate ligament reconstruction outcomes: A systematic review. Knee Surg Sports Traumatol Arthrosc 2015;23:752-62.
Kvist J, Ek A, Sporrstedt K, Good L. Fear of re-injury: A hindrance for returning to sports after anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc 2005;13:393-7.
Webster KE, Feller JA, Lambros C. Development and preliminary validation of a scale to measure the psychological impact of returning to sport following anterior cruciate ligament reconstruction surgery. Phys Ther Sport 2008;9:9-15.
Kvist J, Österberg A, Gauffin H, Tagesson S, Webster K, Ardern C. Translation and measurement properties of the Swedish version of ACL-Return to Sports after Injury questionnaire. Scand J Med Sci Sports 2013;23:568-75.
Bohu Y, Klouche S, Lefevre N, Webster K, Herman S. Translation, cross-cultural adaptation and validation of the French version of the Anterior Cruciate Ligament-Return to Sport after Injury (ACL-RSI) scale. Knee Surg Sports Traumatol Arthrosc 2015;23:1192-6.
Chen T, Zhang P, Li Y, Webster K, Zhang J, Yao W, et al
. Translation, cultural adaptation and validation of simplified Chinese version of the anterior cruciate ligament return to sport after injury (ACL-RSI) scale. PLoS One 2017;12:e0183095.
Harput G, Tok D, Ulusoy B, Eraslan L, Yildiz TI, Turgut E, et al
. Translation and cross-cultural adaptation of the anterior cruciate ligament-return to sport after injury (ACL-RSI) scale into Turkish. Knee Surg Sports Traumatol Arthrosc 2017;25:159-64.
Slagers AJ, Reininga IH, van den Akker-Scheek I. The Dutch language anterior cruciate ligament return to sport after injury scale (ACL-RSI) – Validity and reliability. J Sports Sci 2017;35:393-401.
Silva LO, Mendes LM, Lima PO, Almeida GP. Translation, cross-adaptation and measurement properties of the Brazilian version of the ACL-RSI Scale and ACL-QoL Questionnaire in patients with anterior cruciate ligament reconstruction. Braz J Phys Ther 2018;22:127-34.
Ha JK, Kim JG, Yoon KH, Wang JH, Seon JK, Bae JH, et al
. Korean version of the anterior cruciate ligament-return to sport after injury scale: Translation and cross-cultural adaptation. Clin Orthop Surg 2019;11:164-9.
Salatkaitė S, Šiupšinskas L, Gudas R. Translation and cultural adaptation of Lithuanian version of the anterior cruciate ligament return to sport after injury (ACL-RSI) scale. PLoS One 2019;14:e021959.
Hirohata K, Aizawa J, Furuya H, Mitomo S, Ohmi T, Ohji S, et al
. The Japanese version of the anterior cruciate ligament-return to sport after injury (ACL-RSI) scale has acceptable validity and reliability. Knee Surg Sports Traumatol Arthrosc 2020;28:2519-25.
Sala-Barat E, Álvarez-Díaz P, Alentorn-Geli E, Webster KE, Cugat R, Tomás-Sabado J. Translation, cross-cultural adaptation, validation, and measurement properties of the Spanish version of the anterior cruciate ligament-return to sport after injury (ACL-RSI-Sp) scale. Knee Surg Sports Traumatol Arthrosc 2020;28:833-9.
Müller U, Krüger-Franke M, Schmidt M, Rosemeyer B. Predictive parameters for return to pre-injury level of sport 6 months following anterior cruciate ligament reconstruction surgery. Knee Surg Sports Traumatol Arthrosc 2015;23:3623-31.
Beaton DE, Bombardier C, Guillemin F, Ferraz MB. Guidelines for the process of cross-cultural adaptation of self-report measures. Spine (Phila Pa 1976) 2000;25:3186-91.
Almangoush A, Herrington L, Attia I, Jones R, Aldawoudy A, Abdul Aziz A, et al
. Cross-cultural adaptation, reliability, internal consistency and validation of the Arabic version of the knee injury and osteoarthritis outcome score (KOOS) for Egyptian people with knee injuries. Osteoarthritis Cartilage 2013;21:1855-64.
Roos EM, Roos HP, Ekdahl C, Lohmander LS. Knee injury and Osteoarthritis Outcome Score (KOOS)-validation of a Swedish version. Scand J Med Sci Sports 1998;8:439-48.
Coons SJ, Alabdulmohsin SA, Draugalis JR, Hays RD. Reliability of an Arabic version of the RAND-36 Health Survey and its equivalence to the US-English version. Med Care 1998;36:428-32.
Flandry F, Hunt JP, Terry GC, Hughston JC. Analysis of subjective knee complaints using visual analog scales. Am J Sports Med 1991;19:112-8.
Prinsen CA, Mokkink LB, Bouter LM, Alonso J, Patrick DL, De Vet HC, et al
. COSMIN guideline for systematic reviews of patient-reported outcome measures. Quality of Life Research 2018; 27:1147-57.
Souza AC, Alexandre NM, Guirardello EB. Psychometric properties in instruments evaluation of reliability and validity. Epidemiol Serv Saude 2017;26:649-59.
Terwee CB, Bot SD, de Boer MR, van der Windt DA, Knol DL, Dekker J, et al
. Quality criteria were proposed for measurement properties of health status questionnaires. J Clin Epidemiol 2007;60:34-42.
Baumgartner T. Norm-referenced measurement: Reliability. In: Measurement Concepts in Physical Education and Exercise Science. Vol. 45-72. Champaign, IL: Human Kinetics; 1989.
Streiner DL, Norman GR, Cairney J. Health Measurement Scales: A Practical Guide to Their Development and Use. 5th
ed. New York: Oxford University Press; 2015.
Coppieters M, Stappaerts K, Janssens K, Jull G. Reliability of detecting 'onset of pain' and 'submaximal pain' during neural provocation testing of the upper quadrant. Physiother Res Int 2002;7:146-56.
[Table 1], [Table 2]