İbrahim Taka1, Berat M. Alkan2, Fatma F. Yıldız2

1Department of Physical Medicine and Rehabilitation, Ankara Training and Research Hospital, Ankara, Türkiye
2Department of Physical Medicine and Rehabilitation, Ankara City Hospital, Ankara, Türkiye

Keywords: Duruöz Hand Index, factor analysis, lateral epicondylitis, reliability, validity.

Abstract

Objectives: This study aims to investigate the validity, reliability and clinimetric features of the Duruöz Hand Index (DHI) in patients with lateral epicondylitis.

Patients and methods: Between October 2019 and January 2020, a total of 78 patients (28 males, 50 females; mean age: 46.4±9.4 years; range, 20 to 65 years) who presented with pain in the forearm and were diagnosed with lateral epicondylitis were included in the study. The patients were evaluated using the Visual Analog Scale (VAS), Health Assessment Questionnaire (HAQ), the Patient-Rated Tennis Elbow Evaluation Questionnaire (PRTEEQ), the Disabilities of the Arm, Shoulder and Hand (DASH) Questionnaire at Weeks 0, 1 and 4. The DHI reliability (Cronbach alpha, intraclass correlation [ICC]), validity and factor analyses were performed with the data of 70 and 49 patients who attended to follow-up visit at Weeks 1 and 4. The effect size (ES), standard response mean (SRM), and minimum detectable change (MDC) values of the DHI were calculated.

Results: Of the patients, 84.6% were right-handed. The ICC coefficients of DHI were found to be perfect with the test-retest method (ICC; total=0.943). It showed a well-excellent consistency with the internal consistency method (Cronbach alpha; total=0.90). In the structural validity of the DHI, it was very strongly correlated with the DASH (r=0.801; p<0.01), strongly correlated with the PRTEEQ and HAQ total scores (r=0.793; p<0.01; r=0.785; p<0.01), and acceptably correlated with PRTEEQ pain score (r=0.570; p<0.01). The DHI was acceptably correlated with the VAS and grip strength as measured by the hand dynamometer (p<0.05). In our study, three main factors were obtained and MDC and responsiveness sensitivity were found to be moderate (MDC=4.4; SEM=1.61; ES=0.246 p<0.001; SRM=0.538 p<0.001).

Conclusion: Duruöz Hand Index is a reliable, valid, and practical functional assessment scale in patients with lateral epicondylitis.

Introduction

Lateral epicondylitis is a degenerative disease characterized by pain around the lateral epicondyle, often due to overuse of the forearm. In the general population, its incidence has been reported as 0.5% with a prevalence of 3%, often affecting individuals aged between 30 and 60 years.[1,2]

For the elbow joint, which has a complex structure, correct positioning in space for fine movements of the hand, strong grip and substantial support for forearm functions are important.[3] Due to pain and deformation in lateral epicondylitis, elbow-forearm functions, hand grip strength, and activities requiring fine skills are affected. Considering the impact to the quality of life, it is critical to measure the level of exposure with objective daily living activities and disability tests. The Health Assessment Questionnaire (HAQ), the Patient-Rated Tennis Elbow Evaluation Questionnaire (PRTEEQ), the Disabilities of the Arm, Shoulder and Hand (DASH) Questionnaire are commonly used assessment scales in cases of lateral epicondylitis.

The validity and reliability of the Duruöz Hand Index (DHI) has been proven in many diseases related to upper extremity; however, it has not been studied in patients with lateral epicondylitis. This test does not require any additional training or equipment and can be performed easily and rapidly. In the present study, we aimed to investigate the validity, reliability, and clinimetric features of the DHI in patients with lateral epicondylitis.

Patients and Methods

This cross-sectional, prospective study was conducted at Physical Medicine and Rehabilitation outpatient clinic of Ankara City Hospital between October 2019 and January 2020. A total of 78 patients (28 males, 50 females; mean age: 46.4±9.4 years; range, 20 to 65 years) who presented with pain in the forearm and were diagnosed with lateral epicondylitis were included in the study. Inclusion criteria were as follows: pain in the forearm for at least three weeks, age range between 18 and 65 years, increased pain in the lateral epicondyle region with pressure and resistant extension of the wrist and at the same time, and positive Mill’s test. Exclusion criteria were as follows: having bilateral lateral epicondylitis, signs of osteoarthritis in the elbow on X-ray, receiving treatment for lateral epicondylitis within the past six months, presence of cervical radiculopathy, history of surgery or trauma in the forearm, accompanying inflammatory arthritis, malignancy, myopathy, and common painful diseases such as fibromyalgia.

The flow of the study as seen in the flowchart (Figure 1); In the first evaluation, clinical and demographic data such as age, sex, education status, marital status, disease duration, tobacco/alcohol use, risk factors, dominant hand and pain levels of patients were recorded. Functionality, grip strength, and quality of life were also assessed. Necessary information was given to all patients, and rest, protection and exercise methods were also explained. All patients were advised to use non-steroidal anti-inflammatory drugs (NSAIDs) and elbow splints. The patients were re-evaluated after one and four weeks, and measured again DHI, DASH, and PRTEEQ for validity, reliability, and responsiveness.

Assessment scales

The Visual Analog Scale (VAS): The rest, activity, and night pain of the patients were evaluated with VAS. Zero corresponding to no pain, 10 corresponding to the most severe pain the patient has ever experienced in their life.

Grip force: Painless grip strength, which is commonly used in patients with tennis elbow and is more sensitive to change than maximum grip strength, was recorded.[4] The patients were instructed to squeeze the Baseline® digital hydraulic hand dynamometer (Fabrication Enterprises Inc., New York, USA) as much as possible until experiencing pain and to stop when the pain starts. The assessment was performed, while the patient was in a sitting position with shoulder abduction, elbow flexion and the wrist in neutral. Three consecutive measurements were made from both the painful and the intact arm by allowing enough time to rest in between tests and the results were recorded and average values were considered.[4,5]

Health Assessment Questionnaire: The daily living activities of the patients and their level of disability were evaluated with the HAQ. The test consists of 20 questions in total. Activities of daily living are evaluated separately: dressing, standing up, eating, walking, hygiene, reaching, grasping, and daily chores. Questions are answered according to the Likert scale (0= No difficulty, 1= Some difficulty, 2= Much difficulty, 3= Unable to do). Minimum 0 maximum 60 points are divided by 20 and scored in the range of 0 to 3 points. Low scores on this test indicate better functional status.[6]

Disabilities of the Arm, Shoulder and Hand: This is a commonly used disability test with validity and reliability in arm, shoulder, and hand problems that cause pain and disability. The test consists of 30 questions and has two parts. The first 21 questions assess the effect of arm, shoulder and hand problems on daily living activities using the Likert scale. The remaining nine questions assess the effect of the current ailment on social life, sleep, work, and the level of pain-tingling-weakness-difficulty in movement. The score obtained is calculated by dividing the score by the number of questions answered with minimum of 0 to maximum of 100 points, and the lower score indicates the better functional status.[7]

Patient-Rated Tennis Elbow Evaluation Questionnaire: This scale consists of two parts with 15 questions each. The first part assesses pain in the forearm, and the second part assesses functionality. The second part is divided into specific functions (six questions) and general functions (four questions) and consists of a total of 10 questions. The questions are answered with a numerical evaluation scale ranging from 1 to 10. Score is calculated with the formula of pain score +1/2 (specific functions + general functions) to get a minimum of 10 and a maximum of 100 points. The average of the general functions score with the specific functions score creates the function score. Low scores on the test indicate better functional status.[8]

Duruöz Hand Index: The test consists of 18 questions. It is a simple questionnaire that separates daily living functions (kitchen work, getting dressed, cleaning, work, and other daily living activities), does not require an additional training or equipment, and takes approximately 5 min to complete. Lower scores indicate better functional status in a test that can be obtained from a minimum of 0 to a maximum of 90 points arranged using the Likert scale.

The DHI was first developed in 1996 for the evaluation of hand functions in patients with rheumatoid arthritis and subsequently its validity (face, criteria, content, construct) and reliability (inter-rater, intra-rater, test-retest, internal consistency) were investigated in many diseases. Normative data of DHI (5.8±9.58-50.88±27.25), standard error of measurement of the scale (SEM; 0.52-5.92), minimum detectable change value (MDC; 1.4-16.37), responsiveness values (SRM=standard response mean; 0.26-1.97, ES=effect size; 0.24-1.39) were identified in previous studies.[9]

DHI assessment

Reliability: The scale should be error-free and stable and it should be trusted that the same results would be obtained in a re-measurement. The test-retest method is an up-to-date and value-preserving method. In this method, after the questionnaire is applied once, the test is repeated at a date that is far enough not to disturb the measurement standards and is not too close to be remembered. The correlation coefficient between the two measurements is calculated. This calculation yields the reliability coefficient. A reliable and frequently used method for scales from internal consistency methods is Cronbach alpha internal consistency coefficient calculation method. The reliability of the DHI was evaluated using test- retest and internal consistency methods.[10,11] For the test-retest method, the patients completed the DHI twice with an interval of seven days.

Validity: Validity is the degree to which a scale can measure what is intended. The scale is examined in terms of face, content, criterion and construct for validity. For content validity, the gold-standard measurement method in that area, if any previously performed is compared with the tested measurement method. The validity coefficient is obtained with the correlation coefficient. Prediction and concurrent validity can be considered for criterion validity. Construct validity is based on the detection of certain items related to each other or the relationships between items.[10,11] In this study, the content, criteria and construct validity of the DHI were examined.

Exploratory factor analysis: The reliability of the measurement elements to represent factors or theoretical constructs is tested. It represents the grouping of observation variables in the principal component data set into linear composite variables by principal component analysis method and new unrelated variables are revealed. In order for the scale to be tested firstly the Kaiser-Meyer-Olkin (KMO) and Bartlett's test must be appropriate.[10,11]

Confirmatory factor analysis: Using this analysis, the compatibility of the model desired to be measured in theory with the data obtained as a result of the measurement is investigated. To perform the analysis, first a model of theoretically observed variables and patterned variables is drawn and, then, the interactions between the models are generated using the path diagram, finally appropriate analysis is performed.[10,11]

The MDC is the minimum amount of change that cannot be attributed to measurement error in a measurement to express a significant change in a test. It can be calculated using the formula (1,96X√2XSE), which is a method measured with the standard error (SE) of the measurement at 95% confidence interval (CI).[12]

Responsiveness is the sensitivity of the test to change over time in the patient, which may be an indicator of therapeutic effects. Responsiveness can be measured internally and externally. Internal measurement method can be measured by effect size calculation.[13]

Statistical analysis

Power analysis and sample size calculation were performed using the G*Power 3.1.9.4 software (Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany). Accordingly, 45 patients were sufficient to be recruited for this study (effect size: 0.5; power[1-β]>0.95).

Statistical analysis was performed using the IBM SPSS version 22.0 (IBM Corp., Armonk, NY, USA) and Amos version 24.0 software (IBM Corp., Armonk, NY, USA). Descriptive data were expressed in mean ± standard deviation (SD), median (min-max) or number and frequency, where applicable. The distribution of the variables was measured using the Kolmogorov-Smirnov and Shapiro-Wilk tests. Repeated measurements were analyzed using the paired t-test for the parametric data and the Wilcoxon test for the non-parametric data. To show and verify the consistency between the factors, exploratory and confirmatory factor analyses were performed in accordance with the structural equation model. The KMO sampling fit measurement and Bartlett’s test were used in exploratory factor analysis. A KMO test close to 1 shows high compatibility, and close to 0, it shows low compatibility. Correlation matrix analysis was performed using the Factor Analysis Principal Components method. In-factor weights of implicit variables were calculated using the Varimax rotation method. Factors with a total eigenvalue ≥1 were accepted and considered significant, if the cumulative variance was more than 50%. Factors with a total eigenvalue of ≥0.3 of implicit variables were considered significant in the intra-factor distribution. For confirmatory factor analysis, structural equality modeling was performed according to the scale. In the subsequent analysis, The goodness-of-fit Index, confirmatory fit index, and normed fit index values were considered higher than 0.90 for acceptable fit. The root mean square approximation error (RMSAE) values were considered very good, if ≤0.05, good if >0.05-0.08, and poor fit if ≥0.10. For validity analysis, Cronbach alpha values and intraclass correlation (ICC) coefficients were calculated for the entire index and individual subgroups. Cronbach alpha value was considered weak between 0.00-0.69, acceptable between 0.70-0.79, good between 0.80-0.89 and excellent between 0.90-1. The Spearman and Pearson correlation tests were used to evaluate both the internal consistency of the DHI and the relationship between the PRTEEQ and DASH Questionnaire. Effect size and standardized response mean values were calculated to determine the test's responsivity value. A p value of <0.05 was considered statistically significant.

Results

Demographic characteristics of patients are shown in Table 1. The mean values of the hand dynamometer results in the unaffected arm were significantly higher (p<0.01). Table 2 shows the patients' resting pain, movement pain with heavy lifting, and night pain measured with a VAS, and hand the dynamometer measurements. The HAQ was used in the initial evaluation of the patients, and the quality of life results are shown in Table 2. The DASH and PRTEEQ were measured twice at Weeks 0 and 4 (Table 2). The difference between the first and second values was found to be significant compared to the paired t-test (p<0.01). The DHI was repeated three times at Weeks 0, 1(for reliability), and 4 (for responsiveness) of the study (Table 3).




Reliability: In this study, the test-retest method and the Cronbach's alpha method were used for the reproductivity and internal consistency of the Duruöz Hand Index. Intraclass correlation coefficients (ICC) values between 0.00-0.39 indicates weak, between 0.4-0.74 indicates adequate and between 0.75-1 indicates excellent agreement. Cronbach's alpha values between 0.00-0.69 indicates weak, between 0.70-0.79 indicates acceptable, between 0.80-0.89 indicates strong and between 0.90-1 indicates excellent fit. Intraclass correlation coefficients and Cronbach's alpha values obtained as a result are shown in Table 4.

Validity: In this study, the content, criteria, and construct validity were examined. Correlation values between -0.2; +0.2 indicates weak, between -0.59; -0.21 and +0.21; +0.59 are indicates acceptable, between -0.79; -0.6 and between +0.6; +0.79 indicates strong, and between -0.99; -0.8 and between +0.8; +0.99 indicates very strong. A value of -1 or +1 indicates perfect concordance. Tables 5 and 6 show the Spearman correlations for the content, criteria, and construct validity tests of the DHI.


Factor analysis: In this study, two types of factor analysis were performed. The results of exploratory factor analysis (factors and components on the scale are revealed) and confirmatory factor analysis (tests the compatibility of the model with the theory) are given in Table 7. Figure 2 shows the structura equality model. The results of confirmatory factor analysis are shown in Table 8.



Other analyses: The MDC value is the minimum amount of change that must be in a measurement that cannot be attributed to a measurement error to express a significant change in the test. In this study, the MDC value was calculated as 4.46 using the formula 1, 96X√2XSE, including SE in the 95% CI (SE=1.61). In our study, ES was known as the classical Glass' method; obtained by dividing the difference between the first and second measurement by the standard deviation of the first measurement and SRM method found by dividing the difference between the first and second measurement by the standard deviation of this difference values were calculated. The effect size and SRM values were considered clinically meaningless, if <0.2, low sensitivity if 0.21-0.50, medium sensitivity between 0.51-0.79, and high sensitivity if >0.80. The ES and SRM values are shown in Table 9.

Discussion

In order to be effective to patients in clinical practice, it is necessary to develop robust scales or to demonstrate the validity of existing powerful scales in definite patient groups. In this study, DHI was shown to be a reliable and valid scale in patients with lateral epicondylitis.

In order for the scale used in the collection of scientific data to be a standard measurement, it must have some psychometric strength. The psychometric integrity of the test depends on whether the test is valid and reliable and whether the norms are formed in a similar group. These concepts indicate whether the test measures what it is intended to measure and whether the result of the test changes across different measurements.[11] When the data of 78 patients with lateral epicondylitis were examined by the test-retest method, it was found that the DHI was perfectly correlated for the total score and subtitle separately (ICC coefficients; total=0.943).

In order to check reliability, inter-rater reliability is measured by checking the correlation between the two applicators and the application of a single form. Intra-rater reliability is the degree of compatibility between multiple measurements made by a single reviewer. The ICC coefficients are used in these measurements. Intra-rater ICC of testretest validity in the DHI was studied by Duruöz et al.[15] in patients with rheumatoid arthritis (ICC=0.97-excellent) and by Poiraudeau et al.[14] in patients with hand osteoarthritis (ICC=0.96- excellent) and found to be excellent. The DHI has been previously studied in patients with rheumatoid arthritis, stroke, scleroderma, cerebral palsy, carpal tunnel syndrome, and tendon injury. In these studies, similar to our study, the ICC coefficients of the total score of the DHI and the observable variables in all subscales were also interpreted as excellent.[14-23]

When the data of the patients with lateral epicondylitis were examined, the DHI showed good-excellent consistency with the internal consistency (Cronbach alpha; total=0.90; kitchen=0.94; wearing=0.75; cleaning=0.70; work=0.88; other=0.85) method and, in general, the DHI was reliable in patients with lateral epicondylitis. Similar to our results, Sezer et al.[17] studied Cronbach alpha internal consistency coefficients for DHI found to be excellent within the structure and in all patterns (0.91-0.97). In another study, Goksenoglu et al.[22] showed an excellent consistency in the structure and patterns (0.91-0.97) without activities at work section and a good consistency for activities at work (0.828). Erçalık et al.[21] showed a good consistency in the structure and patterns outside the department of activities at work (0.834-0.879) and an excellent consistency for activities at work (0.977).[17,21,22]

In this study, the validity of the DHI in terms of coverage, criteria, and structure in patients with lateral epicondylitis were analyzed. The relationship between structure validity and elements was investigated which forms the basis of the validity of the scale. It was examined under divergent and convergent validity. Convergent validity investigates the existence of a relationship between questionnaires that evaluate the prespecified situation, while divergent validity examines the existence of a relationship between measurements that evaluate a prespecified situation. In convergent structure validity, DHI was found to be very strongly correlated with DASH, PRTEEQ function score, daily activities score, total score, and HAQ total score, and to be acceptably correlated with PRTEEQ pain score. In the validity of the divergent structure, VAS rest pain, activity pain, night pain, and the grip force of the hand dynamometer were found to be acceptable correlated with DHI. Our observations during our study also showed that the patients understood the questions well. Similar to our study, the construct validity was found to be strong in many DHI validity studies.[15,17,19-25] As a consequence, the DHI indicates that it is a valid (content, construct, criterion, and face) and reliable (norm-reference and internal consistency) functional assessment scale in patients with lateral epicondylitis.

The DHI was evaluated by factor analysis in the development study and in subsequent studies.[15,16,24] In this study, when the data of the patients with lateral epicondylitis were examined by principal component analysis method, DHI questioned three basic factors and these factors were associated with activities that require strength of the hand and forearm, flexibility with grip strength of the hand, and activities requiring fine dexterity of the hand (KMO value=0.880; Bartlett's test p<0.01). In the study conducted by Duruöz et al.[15] which is the main study, in patients with rheumatoid arthritis, principal component analysis method and correlation matrix were used and varimax method, which brings the variance to the highest value, was preferred. As a result of the analysis, three basic factors were obtained. The first factor was associated with the power and rotation movements of the hand, the second factor was associated with the dexterity of the hand, and the third factor was associated with the flexibility of the first three fingers of the hand. In the study of Poiraudeau et al.,[24] four main factors were identified. The first factor was associated with grip strength, the second factor with dexterity, the third factor with grip strength, and the fourth factor with grip skill.

The fact that the basic factors obtained were different in this study and in other studies can be explained by the fact that the same questions may have different meanings in different diseases. Already, the goal of factor analysis is to attempt to detect this condition. The inability to show a good fit in the fit indexes with the maximum likelihood estimation method in this study can be explained by the low number of participants, the fact that the test was not developed for this disease, and the results were incorrect or misinterpreted, as the corrections that could be suggested with the structural equation model were not made for these diseases. The DHI MDC (4,4) value and SEM (1,61) values in patients with lateral epicondylitis were examined and, when evaluated together with the ES (0.246; p<0.001) and SRM values (0.538; p<0.001), the MDC value and responsiveness sensitivity were found to be moderate.

The fact that our study is not multi-center, small number of patients participating for further statistical measurements, the absence of a gold-standard test to compare our study, the lack of inter-observer test-retest validity, the absence of a determined and significant predictive criteria in patients with lateral epicondyle are the main limitations of this study.

In conclusion, the DHI is a reliable, valid, and practical functional assessment scale in patients with lateral epicondylitis. The use of the DHI would be useful in the follow-up of patients and in clinical studies. In addition, the fact that factor analyses caused by a small number of patients do not give clear results suggests that further large-scale studies are needed to draw more reliable conclusions on this subject.

Citation: Taka İ, Alkan BM, Yıldız FF. Validity and reliability of the Duruöz Hand Index in patients with lateral epicondylitis. Arch Rheumatol 2022;37(3):315-325.

Ethics Committee Approval

The study protocol was approved by the Yildirim Beyazit University Faculty of Medicine Ethics Committee (Date: 09/10/2019; No: 101). The study was conducted in accordance with the principles of the Declaration of Helsinki.

Author Contributions

Gathering data, Data analysis, writing the manuscript: ‹.T.; Study plan, data analysis, revising the manuscript: B.M.A.; Gathering data: F.F.Y.

Conflict of Interest

The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

Financial Disclosure

The authors received no financial support for the research and/or authorship of this article.

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