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Revista Facultad de Odontología Universidad de Antioquia

versión impresa ISSN 0121-246X

Rev Fac Odontol Univ Antioq vol.25 no.1 Medellín jul./dic. 2013

 

ORIGINAL ARTICLES DERIVED FROM RESERCH

 

CROSS-CULTURAL ADAPTATION OF RESEARCH DIAGNOSTIC CRITERIA FOR TEMPOROMANDIBULAR DISORDERS (RDC/TMD)

 

 

Yoly González1; Yaritza Miranda-Rivera2; Irene Espinosa3

 

1 DDS, MS, MPH. State University of New York at Buffalo. Doctor Dental Surgery. Magister in Oral Sciences. Periodontics Specialist, Certificate in Orofacial Pain and Temporomandibular Disorders. MSc in Oral Health and Epidemiology. Assistant Professor and President of the Orofacial Pain/Temporomandibular Disorders Clinic, State University of New York at Buffalo. E-mail address: ymg@buffalo.edu

2 MD, MS Universidad de Puerto Rico, State University of New York at Buffalo Oral Sciences, University at Buffalo. Doctor Dental Surgery. Magister in Oral Sciences. Periodontics Specialist, Private Office

3 DHS. Universidad Nacional Autónoma de Móxico. Professor- Researcher, Benemérita Universidad Autónoma de Puebla, México

 

SUMBITTED: NOVEMBER 20/2012-ACCEPTED: FEBRUARY 5/2013

 

González YM, Miranda-Rivera Y, Espinosa I. Cross-cultural adaptation of research diagnostic criteria for temporomandibular disorders (RDC/TMD). Rev Fac Odontol Univ Antioq 2013; 25(1): 11-25.

 

 


ABSTRACT

INTRODUCTION: the goal of this study was to establish the cross-cultural adaptation of Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). METHODS: with a test-retest design, this study evaluated the psychometric properties of RDC/TMD in their Spanish version. Bilingual subjects were evaluated in order to test consistency between the Spanish and English versions of the instrument, including axis I (clinical conditions of TMD) and axis II (psychosocial aspects related to TMD). RESULTS: the reliability of axis I test re-test for diagnosis classification was excellent (Kappa = 1,0). The reliability analysis of axis I test-retest for classifying different diagnoses was also excellent (Kappa = 1,0). Concerning axis II, the intraclass correlation coefficient (ICC) was calculated for Graded Chronic Pain Scale (GCPS) (0,96) as well as for Jaw Disability Checklist (JDC) (0,77), depression (0,87), and nonspecific physical symptoms (0,98). Also, Cronbach's Alpha for JDC was calculated (0,89). Spearman correlations among axis II reagents showed a median of correlation of 0.50 (0.293 to 0.856) with high values between JDC and GCPS. These correlations provide support for internal consistency of RDC/TMD in Spanish. CONCLUSIONS: the demonstrated validity and reliability of the RDC/TMD lie in thier psychometric properties. The cross-cultural adaptation of this instrument allows its use in Spanish-speaking populations for the assessment of the role of TMD in this population.

Key words: temporomandibular disorders, validity and reliability, Hispanic Americans, cross-cultural comparisons.


 

 

INTRODUCTION

Temporomandibular disorders (TMDs) is a collective term for a number of clinical problems affecting masticatory muscles, temporomandibular joints (TMJs), and other associated structures.1 TMDs have been identified as the main cause of orofacial pain of dental origin and are considered a subtype of musculoskeletal disorders.1 The prevalence reported in different study populations ranges between 6.3 and 15% in women and 2.8 to 10% in men in the U.S.2-4 It has also been noted that TMDs present a clear pattern for age-specific prevalence, with the greatest predominance between 35 to 45 years2, 3, 5-7 The most relevant features of TMDs are chronic pain and persistent orofacial pain, which is the main reason why patients seek treatment.2 Masticatory musculature and TMJ sensitivity in response to palpation is frequently reported by patients. Restricted jaw movement and joint sounds elicited by mandibular excursions are probably the clinical determinants to diagnose certain types of TMDs.8

The Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) offer a standardized system that may be evaluated for use in examinations, diagnosis, and classification of the most common subtypes of TMDs.8 Since its introduction in 1992, this instrument has been widely used in research and clinical procedures worldwide.9-11 Total or partial translations of RDC/TMD have been used in studies in different languages including German, Finnish, French, Hebrew, Japanese, Spanish, and Swiss. However, their validity and reliability has not yet been tested in all of these languages as documented by the International RDC/TMD Consortium.

The use of a validated instrument in the Spanish language would allow better chances to diagnose these disorders in Spanish-speaking communities. As stated in the latest U.S. census, Hispanic Americans represent 30% of the population of the entire nation and only half of them report speaking English "very well". Having access to an instrument in their native language will benefit this population, as it would offer a more valid and reliable TMD assessment and therefore proper diagnosis.

Cross-cultural adaptation or equivalence is defined as the process of the required modifications to a translated instrument in order to maximize its cultural properties in the language and culture to which it will be translated. The translation and intent of individual items should be validated within the culture under study in order to ensure that participants in the target language access the equivalent meanings, allowing comparability of data and external validity.12 It is essential to determine whether the concepts exist in the target culture or if they can be used in the same way. This may be achieved by analyzing each item in a specific manner. 13 For example, RDC/TMD usually include a self-report patient questionnaire, which contains items that can be translated with a semantic equivalence across languages without difficulty, such as: "Where were you born?". But there are items that pose special difficulties such as "Do you feel blue?". For the English-speaking culture, "blue" means a state of depression, but for the Hispanic culture that expression would not have the connotation of depression. In fact, many Hispanics will associate "feeling blue" with happiness.

In general, cultural adaptation consists of 5 stages: a) translation, which must be done by at least two independent bilingual translators native in the target language (Spanish)12-15 b) back-translation; for this step, the translator's native language should be the source language (English) and the second one should be the target language (Spanish), c) review committee and reviewers; this committee must provide a final version of the new instrument based on the versions obtained during the previous steps. This committee should be a multidisciplinary panel of experts on both the disease or condition being treated and on the intents of the measures and concepts under study,14, 16, 17 d) pre-testing for equivalences; this would be the final version of the instrument, administered to a group of bilingual individuals with the intention of detecting discrepancies. This method can also be used as an auxiliary and to detect any inadequate details of the final version within the cultural context (with bilingual or monolingual subjects), 14, 17-20 and e) Formal instrument assessment; in this step the instrument is used in a larger sample in order to formally evaluate test validity properties. Subjects should be selected according to the same criteria used in previous steps.21, 22 Initially, RDC/TMD were developed in and for the English language. Their translation and validation have been done in various non-English-speaking populations, allowing the application of transcultural clinical studies.

The goal of this study was to establish the crosscultural adaptation and to assess the validity and reliability of RDC/TMD in bilingual subjects in Eastern New York State.

 

METHODS

The protocol for this study was submitted and approved by the Health Sciences Institutional Review Board (HSIRB) of the State University of New York at Buffalo.

An observational, cross-sectional design was used for field testing the instrument. A test re-test design was used to evaluate reliability of RDC/TMD within bilingual Hispanics. The RDC/TMD consist of: a) a background questionnaire, b) a clinical examination form, c) specifications for the clinical examination, including a set of verbal instructions that are given to patients during physical examination, and d) an algorithmic protocol for scoring axis I and axis II of RDC/TMD.8, 23-25 All these elements were translated from the source language (English) into Spanish by native Spanish speakers, and back-translated into English by natives of this language. A multidisciplinary panel of bilingual and monolingual individuals carefully evaluated the translation and produced the final Spanish version that was used in this study. This document can be digitally accessed in the International RDC/TMD Consortium site.24 A training period was provided in order to master the clinical skills for the proper conduction of this examination protocol. Emphasis was placed not only at the clinical level but also at the commands/instructions level. Relevance of the proper and consistent commands in the original language and the translated version cannot be underestimated as they may directly affect the results of intra- and inter-observer reliability. The clinical training was conducted by the Reference Standard (YG) at the TMD and Orofacial Pain Clinic in the School of Dental Medicine, State University of New York at Buffalo. For application of axis II of the RDC/TMD, both versions (English and Spanish) were reviewed in order to verify parallelism of the items. Axis II score specifications were compared to determine the grade of chronic pain as well as scores of depression and nonspecific physical symptoms.

Subjects

The sample consisted of 33 bilingual subjects proficient in both languages, English and Spanish, who volunteered for the test re-test stage.

Subjects were men and women with and without a diagnosis of TMDs. All study-related doubts were clarified and each subject signed an informed consent as well as the approval of the Health Insurance Portability and Accountability Act (HIPAA). All questionnaires and clinical examinations were administered in both languages. Using a parallel design, the subjects were randomly assigned to one of two groups (Spanish-English or English-Spanish). An interval of about one hour was provided between the administration of the questionnaires and the clinical evaluation from one language to another.

Inclusion criteria were: subjects 18 to 75 years old, born in any country whose native tongue were Spanish, or being part of the first generation of Hispanic descent born in the United States, whose families speak Spanish as a first or second language. Participants were fluently bilingual in both languages, with a clear oral and written understanding of them.

Patient history questionnaire

The RDC/TMD questionnaire (axis II) in both versions consisted of 31 items divided into these variables: socio-demographic, socio-economic, psychological (depression scales and nonspecific physical symptoms, including and excluding pain), psychosocial (intensity and severity of chronic pain degree and disability), the patient's signs and symptoms related to the condition, and jaw disability checklist (limitations related to mandibular functioning).

Clinical evaluation

The RDC/TMD clinical evaluation (axis I) in both versions consisted of 10 items divided into these variables: presence of pain, location of pain, jaw opening pattern, vertical range of mandibular motion, mandibular excursions (laterality and protrusion), joint sounds in mandibular opening and closing, joint sounds in mandibular excursions, and extra- and intraoral muscle pain.

It took 30 minutes for each participant to answer the questionnaire in each language. Once completed, the responses were checked with the participants and clinical evaluations were performed. The evaluation lasted about 15 minutes. Next, each participant was subjected to exactly the same process in the second language as previously described, with a period of about one hour for applying the questionnaire between one language and the other.

Validation process

The validation process was conducted as follows:

    a) Analysis of reliability with a test re-test study of axes I and II of RDC/TMD. The background questionnaire was applied to all the 33 subjects in the same clinic.

    b) Internal consistency (validity) of RDC/TMD axis II assessed the jaw disability checklist and analyzed whether the 12 items were conceptually similar and if they related to each other. Also, correlations between the different variables of RDC/TMD axis II (psychological factors, graded chronic pain scale, and jaw disability) were calculated.

Statistical analysis

Descriptive statistics and chi-square analysis were calculated for all the categorical variables. Additionally, the study's reliability was analyzed by two statistical methods: intraclass correlation coefficient (ICC) was used for the data evaluated with continuous numerical scales (in millimeters), and Cronbach's Alpha was used for categorical variables (presence or absence of joint sounds); values of 0.80 ≤ Κ ≤ 1.0 were used as they were considered to provide excellent reliability. Values of 0.60 ≤ Κ < 0.80 were interpreted as having acceptable reliability, and values of 0.40 ≤ Κ < 0.60 were considered as moderate reliability. These values were used for both statistical methods.26-34

Finally, Spearman correlation was calculated in order to analyze the different variables of RDC/TMD axis II. All the statistical analysis was performed using SPSS, v. 19.

 

RESULTS

Sample characteristics

Table 1 shows the sample's demographic characteristics. Gender representation was balanced. Most subjects were married and income showed a bimodal behavior, with a considerable amount of individuals with an income below US$15,000 per year and a large group of individuals with incomes above US$50,000 a year. The average age was between the fourth and fifth decade of life.

Validity and reliability

Axis I (Clinical TMD conditions)

Analysis of the information from the test re-test of all the 33 participants in this study showed that agreement in all clinical measurements was excellent, with high intraclass correlation coefficients (table 2). Diagnostic reliability of TMDs in the test re-test was also excellent for all types of diagnosis (table 3).

Axis II (pain-disability association, and psychosocial status).

Similarly, the test re-test evaluation was excellent, with an ICC of 0.85 in axis II (table 4).

The evaluation of jaw disability checklist internal consistency (Spanish version) demonstrated a Cronbach's Alpha of 0.80 on full scale evaluation. As shown in table 5, some alpha values slightly increase with the removal of some of the evaluated reagents, such as drinking, exercising, smiling, and keeping one's facial appearance.

The degree of correlation among the different variables of RDC/TMD axis II (tabla 6) was calculated with Spearman Correlation Coefficient, including the subscales of Chronic Pain Grade (CPG), Jaw Disability Checklist (JDC), depression, and nonspecific physical symptoms (NPS). Spearman score was high (r ≥ 0.8) for the correlation of the subscales of JDC/GCP, moderate (r ≥ 0.4) for the subscales of depression/GCP and NPS/JDC, and weak (r < 0.4) for the subscales NPS/GCP, depression/JDC, and depression/NPS.

 

DISCUSSION

 

The goal of this study was to determine the cross-cultural adaptation and to assess the validity and reliability of RDC/TMD (validity of the instrument in English has already been documented).35-37 The present study included subjects of both genders with an average age of 35 years and an adequate level of education, most of whom were married. These demographic characteristics are considered to representative of the population with TMDs.

The fact that all the subjects included in this study were bilingual represents one of its strengths, since the reference standard in this case is the same instrument used in the English version.

Using an instrument in a language other than that in which it was originally designed requires more than a simple translation. It is necessary to show that validity and reliability of the translated instrument are the same as in the original language, with the same interpretation of the reagents, without the subject's cultural background influencing such interpretations. For example, health problems can be expressed in different terms from one culture to another.

In order to assess the validity and reliability of RDC/TMD, the present study used the methodology suggested in the literature.16, 25, 38, 39 The RDC/TMD reagents include several scales with different psychometric capacities, and the validity and reliability of the JDC, based on the list of 12 items included in the instrument, have not yet been evaluated in the Spanish language.

The internal consistency of a set of reagents can be assessed with Cronbach's alpha coefficient, which is an index of reliability for the total score of a set of measures. This coefficient can yield values of 1.0 when the variance of the total score is entirely attributable to the common factors that run through the reagents evaluated.40, 41 For the index of Cronbach's Alpha to be significant, the correlation should not be less than 0.442 but the lowest values used as a reference in clinical studies are of 0.7.43 In the present study, this scale was valid and demonstrated a global alpha index of 0.8, showing its validity and reliability in clinical trials as well as the importance of each of the items of the scale.

Regarding the analysis of Spearman correlation among the different variables of RDC/TMD axis II, the result was an excellent correlation (0.85) between psychosocial variables, GCP and JDC. Correlations between psychological and psychosocial variables (NPS/JDC) were also good (0.418). The scores of depression/GCP were good too (0.42) while depression/ JDC present a weaker correlation (0.36).

Regardless of the analysis of the scale of NPS and depression, the validity of SCL90 (a scale used to assess these symptoms) has been demonstrated in Spanish.44 The above results provide sufficient evidence to conclude that axis II of RDC/TMD works similarly to the original English design. Additionally, axis II was analyzed with ICC and its respective 95% CI. The GCP scale showed an agreement greater than 0.95, the JDC presented an agreement greater than 0.85, and the ICC of depression and nonspecific physical symptoms were similar (0.87 and 0.98 respectively).

Finally, analysis of the RDC/TMD axis I showed excellent agreement with a Kappa of 1.0 for all types of diagnostic protocol, agreeing with results reported in the literature.37, 45

The above findings support the validity and consistency of RDC/TMD. Similarly, other studies have demonstrated the validity of this instrument in languages other than the original one.24, 39, 46

 

CONCLUSIONS

 

The psychometric properties demonstrated in the present study (validity, reliability, and cultural adaptation) make of RDC/TMD a valid and reliable instrument for the assessment of TMDs in the Spanish language.

 

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