IJSPT
ORIGINAL RESEARCH
THE MINIMUM CLINICALLY IMPORTANT DIFFERENCE ON THE VISA-A AND LEFS FOR PATIENTS WITH INSERTIONAL ACHILLES TENDINOPATHY Joshua McCormack, PT, PhD, OCS1,2 Frank Underwood, PT, PhD, ECS1,3 Emily Slaven, PT, PhD, OCS, FAAOMPT, Cert. MDT4 Thomas Cappaert, ATC, PhD, CSCS1
ABSTRACT Study Design: Cohort study of subjects with insertional Achilles tendinopathy (IAT). Objectives: The purpose of this study was to establish the minimum clinically important difference (MCID) on the Victorian Institute of Sport Assessment - Achilles Questionnaire (VISA-A) and the Lower Extremity Functional Scale (LEFS) for patients with IAT. Background: The VISA-A and LEFS are two measures commonly utilized for patients with IAT. Previous authors have estimated the MCID for the VISA-A, but a MCID has not been formally established. The MCID for the LEFS has been established for patients with lower extremity conditions in general, but it is not clear if this MCID is applicable to patients with IAT. Methods: Fifteen subjects participating in a randomized controlled trial studying the effectiveness of intervention for IAT over a 12-week period were included in this study. Subjects completed the VISA-A and LEFS forms at baseline and 12 weeks after the initiation of treatment. All subjects also completed a 15-point global rating of change (GROC) questionnaire at 12 weeks after the initiation of treatment. Subjects were classified as improved or stable based on their GROC scores. Results: The area under the curve (AUC) for the VISA-A was 0.97 and a MCID of 6.5 points was identified. The AUC for the LEFS was 0.97 and a MCID of 12 points was identified. Conclusion: The VISA-A and LEFS are both useful outcome measures to assess response in patients with IAT. Level of Evidence: 3 Keywords: Achilles tendinopathy, LEFS, MCID, VISA-A
1
Rocky Mountain University of Health Professions, Provo, UT Indiana University Health Ball Memorial Hospital, Muncie, IN 3 University of Evansville, Evansville, IN 4 University of Indianapolis, Indianapolis, IN 2
This research was partially funded by Performance Dynamics, Muncie, IN. This funding was utilized to provide gift card incentives to research participants only. Performance Dynamics played no role in the study design, conduct, and reporting or in manuscript publication decisions. This study was approved by the Institutional Review Boards at Rocky Mountain University of Health Professions and Indiana University Health Ball Memorial Hospital. The original study was registered on ClinicalTrials.gov. Registration number: NCT01988155
CORRESPONDING AUTHOR Joshua McCormack 3600 W Bethel Ave Muncie, IN, 47304 E-mail:
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INTRODUCTION Achilles tendinopathy is the most common cause of posterior heel pain with a reported prevalence of 11-18%.1-3 Whereas runners represent the group most likely to develop Achilles tendinopathy, it can also occur in any other type of athlete as well as in sedentary individuals.4,5 Achilles tendinopathy is typically classified as insertional or mid-portion based on the location of pain; insertional Achilles tendinopathy (IAT) causes pain at or near the point where the Achilles tendon attaches to the posterior calcaneus while mid-portion Achilles tendinopathy causes pain 2-7 cm proximal to the calcaneal attachment.6 The Victorian Institute of Sport Assessment – Achilles questionnaire (VISA-A) is a self-administered form that is commonly used to evaluate the severity of Achilles tendinopathy and to monitor outcomes after treatment.7,8 It has previously been shown to be valid, reliable (r = 0.90 to 0.93), and clinically relevant.7, 8 VISA-A scores range from 0 - 100 with higher scores indicative of better function. A score of 90 has been reported to represent full recovery following Achilles tendinopathy.7,9 The Lower Extremity Functional Scale (LEFS) is another valid and reliable (r = 0.86 to 0.94) self-report questionnaire used to assess the function of patients with lower extremity orthopedic conditions, including Achilles tendinopathy.10 Scores on the LEFS can range from 0-80 with higher scores representing better function.10 In order for an outcome tool to be the useful for clinicians and researchers, the minimum clinically important difference (MCID) should be established. The MCID is defined as the smallest change on a scale that would be considered important to a patient.11-13 The MCID allows clinicians to evaluate pre- and post-treatment outcome scores to determine if the amount of change that occurred would be perceived as meaningful.13 The MCID is useful to researchers when determining sample size requirements for studies and when examining results for clinical importance.13 In regards to the VISA-A, no MCID has been formally established, but it has been estimated to fall between 12 and 20 points.7,14-16 The MCID for the LEFS has been previously reported as 9 points.10 However, this MCID was established for patients with a variety of lower extremity conditions and the study did not include any subjects with
Achilles tendinopathy.10 Therefore, a specific MCID for Achilles tendinopathy may be useful. There have been several methods described for identifying an MCID though the most commonly used methods compare the change score on a scale to an external standard of clinically meaningful change.6 The most commonly used external standard is the Global Rating of Change scale (GROC) and recent research has supported the validity of this method.6,8 The GROC requires patients to rate the change in their symptoms on a 15-point scale (-7 to +7) and ratings of +4 (moderately better) or higher have been proposed to represent clinically meaningful improvement.1,6,8 The purpose of this study was to establish the MCID on two patient reported outcome assessments commonly used for patients with Achilles tendinopathy. Specifically, the authors’ sought out to determine the MCIDs on the VISA-A and the LEFS for patients with IAT. METHODS This study was performed as part of randomized controlled trial examining the effects of Astym® and eccentric exercise in the management of IAT. The study was approved by the Institutional Review Boards at Rocky Mountain University of Health Professions and Indiana University Health Ball Memorial Hospital. All subjects signed an informed consent form prior to participation, and the rights of the subjects were protected. All aspects of this study took place at an Indiana University Health Ball Memorial Hospital outpatient rehabilitation clinic between December 2013 and December 2014. Subjects Fifteen subjects over the age of 18 years with IAT participated in this study (Table 1). Inclusion criteria include the following: diagnosis of IAT as a primary complaint, symptom duration of at least six weeks, and a VISA-A score of 78 or lower. Exclusion criteria consisted of: prior treatment with eccentric exercise or Astym® for Achilles tendinopathy, currently taking anticoagulant medication, previous Achilles surgery on the involved side, bilateral symptoms, workers’ compensation or liability cases, peripheral neuropathy, pregnancy, signs of lumbar radiculopathy,
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Table 1. Baseline Demographics and Clinical Characteristics of Subjects
Gender (M/F) Age (SD) BMI Duraon of symptoms in weeks (SD) Smoker Diabetes VISA-A baseline(SD) 12 week VISA-A (SD) LEFS baseline (SD) 12 week LEFS (SD)
Stable (n=3)
Improved (n=12)
p-value
1/2 52.7 (9.7) 41.6 (13.7) 16.3 (10.0) 0 1 36.3 (22.4) 39.3 (20.6) 48.0 (15.7) 51.7 (11.5)
3/9 53.5 (9.1) 36.4 (7.4) 23.2 (13.6) 1 2 38.5 (18.1) 72.3 (19.9) 41.3 (12.0) 63.5 (10.6)
0.77 0.89 0.37 0.44 0.61 0.52 0.86 0.02 0.45 0.11
Abbreviations: SD = standard deviation
inability to complete the required outcomes forms or comply with the recommended treatment regimen. The presence of IAT was clinically determined by the primary investigator using the following criteria: pain at or within two centimeters of the posterior calcaneal insertion of the Achilles tendon along with localized tenderness and a subjective report of decreased activity levels secondary to Achilles pain.17, 18 Subjects were allowed to have additional pathology such as Haglund’s deformity, bone spurs, calcium deposits, and bursa pathology.19 Procedures Subjects were randomly assigned to one of two treatment groups. One group performed a previously described eccentric exercise program designed for patients with IAT.20 The second group received Astym® treatment for up to 12 visits in addition to performing the same eccentric exercise program. Outcomes, including the VISA-A and LEFS, were assessed at baseline, four weeks, eight weeks, and 12 weeks. For the purposes of this study, baseline and 12 week scores were utilized. A 15-point GROC21 questionnaire was also completed by subjects at the 12 week follow up period. Subjects with scores of +4 or higher were considered to have experienced a clinically important improvement.13, 21, 22 Subjects with scores of +3 or lower were considered to have not experienced a clinically important improvement. Statistical Analysis Statistical analyses were performed using SPSS Version 22.0 (SPSS Inc, Chicago, IL). A receiver operating
characteristic (ROC) curve was created using VISA-A change scores from baseline to 12 weeks and dichotomous status on the GROC (+4 and higher, +3 and lower). The point on the curve nearest the upper left hand corner was selected as the cut off score for the MCID to maximize sensitivity and specificity.13 The same procedure was repeated using LEFS change scores from baseline to 12 weeks. RESULTS A total of 15 subjects completed the study. The mean GROC score was 4.7 (SD = 2.0). Three subjects were classified as remaining stable (+3 and lower on the GROC), while 12 subjects were classified as improving (+4 and higher on the GROC). Baseline characteristics as well as follow up scores on the VISA-A and LEFS are presented for the stable and improved groups in Table 1. The area under the curve (AUC) for the VISA-A was 0.94 (CI95% = 0.85-1.0) (Figure 1). The cutoff selected for the MCID was 6.5 points (sensitivity = 0.92, specificity = 1.0) (Figure 2). The AUC for the LEFS was 0.97 (CI95% = 0.89-1.0) (Figure 3). The cutoff selected for the MCID was 12 points (sensitivity = 0.92, specificity = 1.0) (Figure 4). DISCUSSION This is the first study that has prospectively sought out to identify the MCID of two commonly utilized self-report outcome measures for patients with IAT. In the current study a MCID of 6.5 points was identified for the VISA-A and of 12 points for the LEFS. Additionally, the relatively high AUC for both the
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Figure 1. ROC for the VISA-A
Figure 3. ROC for the LEFS
Change in
Change in
VISA-A Score
Sensitivity
1 - Specificity
LEFS score
Sensitivity
1 - Specificity
.0000
1.000
1.000
-1.0000
1.000
1.000
1.5000
1.000
.667
4.0000
1.000
.333
2.5000
.917
.667
9.5000
.917
.333
4.0000
.917
.333
12.0000
.917
.000
6.5000
.917
.000
15.5000
.833
.000
9.0000
.833
.000
18.5000
.667
.000
14.0000
.750
.000
20.5000
.583
.000
21.0000
.667
.000
23.0000
.500
.000
24.5000
.583
.000
24.5000
.417
.000
34.0000
.500
.000
26.0000
.333
.000
44.5000
.417
.000
27.5000
.167
.000
48.0000
.333
.000
33.0000
.083
.000
51.0000
.250
.000
39.0000
.000
.000
55.5000
.167
.000
63.5000
.083
.000
69.0000
.000
.000
Figure 2. Sensitivity and 1-Specificity Values Identified for the VISA-A at Multiple Cut Off Points
VISA-A (0.94) and the LEFS (0.97) confirm that these are useful outcome measures for this population. Even at the lower bounds of the confidence intervals (0.85 and 0.89), these outcome measures would be considered useful.
Figure 4. ensitivity and 1-Specificity Values Identified for the LEFS at Multiple Cut Off Points
The VISA-A is a commonly utilized outcome measure for patients with both insertional and mid-portion Achilles tendinopathy. Although no studies have specifically been conducted to identify the MCID for the VISA-A, previous authors estimated it to fall between 12 and 20 points.7,14-16 However, the authors of a recent systematic review suggested that an accurate estimate could not be established based on existing research.7
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The MCID of 6.5 points identified in this study is notably lower than the previously estimated MCIDs. The fact that none of those studies specifically examined subjects with IAT could account for the discrepancy. The LEFS is another commonly utilized tool for assessing outcomes in patients with lower extremity conditions, including Achilles tendinopathy. The MCID of 12 points identified in this study is similar to the MCID of 9 points previously reported for the LEFS.10 The previous study10 identified the MCID for lower extremity conditions in general, and it does not appear that it included any subjects with Achilles tendinopathy. Therefore, it is reasonable to propose that 12 points may be a more accurate MCID for this specific population. There are limitations to this study that should be considered. First, the sample size was relatively small and a large percentage of subjects were classified as improved. The large AUCs identified in this study could have been influenced by the small sample size and the small number of subjects who were considered to not improve. Therefore the results should be interpreted with caution. However, it should also be noted that the 95% confidence intervals for the AUCs were narrow and even at the lower boundaries would still be considered important. A second limitation is that the authors of the current study examined only one method of establishing the MCID, using the GROC as the external standard of meaningful change. Whereas this is a commonly accepted and utilized practice for establishing an MCID,13, 21-23 concerns have previously been raised that the GROC may not be the best external standard of change.24 However, a more recent study has confirmed the construct validity of using the GROC as a standard of change indicating that it is an appropriate approach.13 In addition to the anchor-based approach for establishing an MCID that was utilized in this study, there are also methods that utilize a distribution-based approach.25 Each approach has specific strengths and weaknesses and no one method has been identified as the best.25 Future studies should seek to validate the results of this study using larger sample sizes and other accepted methods for establishing a MCID. CONCLUSION The results of this study indicate that both the VISA-A and LEFS are useful outcome measures for
patients with IAT that are able to accurately discriminate between individuals who improve over time and individuals who remain stable. The MCIDs of 6.5 points for the VISA-A and an MCID 12 points for the LEFS were identified. These cut-off points can be utilized as indicators of response to treatment for individuals with IAT. However, this should be investigated further with a larger cohort of patients to determine if similar results can be obtained. REFERENCES 1. Solan M, Davies M. Management of insertional tendinopathy of the Achilles tendon. Foot Ankle Clin. 2007;12:597-615, vi. 2. James SL, Bates BT, Osternig LR. Injuries to runners. Am J Sports Med. 1978;6:40-50. 3. Magnussen RA, Dunn WR, Thomson AB. Nonoperative treatment of midportion Achilles tendinopathy: a systematic review. Clin J Sport Med. 2009;19:54-64. 4. Maffulli N. The clinical diagnosis of subcutaneous tear of the Achilles tendon. A prospective study in 174 patients. Am J Sports Med. 1998;26:266-270. 5. Maffulli N, Binfield PM, King JB. Tendon problems in athletic individuals. J Bone Joint Surg Am. 1998;80:142-144. 6. van Dijk CN, van Sterkenburg MN, Wiegerinck JI, et al. Terminology for Achilles tendon related disorders. Knee Surg Sports Traumatol Arthrosc. 2011;19:835-841. 7. Iversen JV, Bartels EM, Langberg H. The victorian institute of sports assessment - achilles questionnaire (visa-a) - a reliable tool for measuring achilles tendinopathy. Int J Sports Phys Ther. 2012;7:76-84. 8. Robinson JM, Cook JL, Purdam C, et al. The VISA-A questionnaire: a valid and reliable index of the clinical severity of Achilles tendinopathy. Br J Sports Med. 2001;35:335-341. 9. Yelland MJ, Sweeting KR, Lyftogt JA, et al. Prolotherapy injections and eccentric loading exercises for painful Achilles tendinosis: a randomised trial. Br J Sports Med. 2011;45:421-428. 10. Binkley JM, Stratford PW, Lott SA, et al. The Lower Extremity Functional Scale (LEFS): scale development, measurement properties, and clinical application. North American Orthopaedic Rehabilitation Research Network. Phys Ther. 1999;79:371-383. 11. Stratford PW, Binkley JM, Riddle DL, et al. Sensitivity to change of the Roland-Morris Back Pain Questionnaire: part 1. Phys Ther. 1998;78:11861196.
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