Validation of the Portuguese version of the Gothenburg Trismus Questionnaire
Validação para a língua portuguesa do Gothenburg Trismus Questionnaire (GTQ)

INTRODUCTION

The term trismus was originally only used for describing the incapacity of patients with tetanus to open their mouths. Currently, it has been widely used to describe any type of restriction in mouth opening after trauma, muscle diseases, or neoplasms, triggered by a primary lesion resulting from surgical procedures or radiotherapy^1,2. The diagnosis of trismus should be based on objective criteria. The measurement of the mouth opening with a millimeter ruler between the upper and lower central incisors at the maximum opening is the most frequently used measurement.

Adults with measurements of < 35 mm are considered as having trismus by most authors^1,3-8. The subjective diagnosis based on the clinical complaint of patients, such as difficulty in mouth opening, mouth locking, and muscle stiffness, should be considered but is less reliable from the scientific point of view^6,7,9,10.

The impact of limited mouth opening on quality-of-life is considered relevant. However, subjective information loses value when this symptom is analyzed in the general context of treatment outcomes. According to Vartanian et al.¹¹, the subjective concept of quality-of-life should be transformed into a quantitative measure so that it can be used both clinically and in research. To this end, questionnaires for assessing quality-of-life are widely used, and the greater the dissemination and administration of standardized questionnaires, the greater their validity in terms of scientific evidence.

Vartanian et al.¹¹ also observed that most of the instruments developed were primarily in English, which may hinder their international use. Simply translating the questionnaire to the language of another country does not ensure that it can be used in that country. For this, a more complex validation process is required. Only after validation can the questionnaire be administered like the original. Several research groups in Brazil have already validated the Portuguese versions of quality-of-life questionnaires to apply them with scientific validation^12,13.

Until recently, quality-of-life questionnaires generally only addressed trismus.

Johnson et al.¹⁴ proposed a quality-of-life questionnaire specific for the assessment of trismus, called Gothenburg Trismus Questionnaire (GTQ), that was developed by the Department of Otorhinolaryngology and Head and Neck Surgery, Sahlgrenska Academy, University of Gothenburg, Sweden, with only its English version validated. Currently, the GTQ is the only questionnaire specific for trismus (Figure 1). It is filled out by the patient and composed of 21 questions divided into 7 domains:

Figure 1 - Letter of acceptance.

Figure 1 - Letter of acceptance.

OBJECTIVE

This study aimed to present and validate the Portuguese version of the GTQ to allow its effective use in Brazilian-speaking populations.

METHODS

The process of validation of the Portuguese version of the GTQ began in January 2014, with a request for authorization from the authors of the original questionnaire, and was completed in July 2015, with its application beginning in September 2014 until July 2015 as part of the validation process.

With the authorization to use and translate the instrument, the validation process was initiated in accordance with the validation procedure proposed by Guillemin et al.^15-17.

The validation process was performed in four steps as follows: translation, retranslation, cultural adaptation, and revalidation:

After completing the 4 steps, the translated and validated GTQ into Portuguese (Figure 2) was administered to a population sample of 30 individuals without oral disorders to assess its effectiveness.

In each domain, the participants answered the questions, marking the most convenient answers qualitatively (e.g., answering the question on mandibular fatigue with “not at all,” “mild,” “moderate,” “severe,” and “very severe”) and assigning scores to the questions so that a higher score meant worse quality-of-life regarding trismus.

For analysis of reproducibility, the internal consistency was assessed using Cronbach’s alpha coefficient, and the reproducibility of the test-retest was assessed using the intraclass correlation coefficient. For the assessment of construct validity, the Pearson and Spearman correlation tests were used for continuous and categorical variables, respectively¹⁸.

RESULTS

The GTQ was successfully translated and was validated and approved by the original authors (Figure 1).

The administration of the GTQ questionnaire took an average of 15 minutes in the selected sample of patients. As this is a sample of asymptomatic cases, the scores showed no trismus.

DISCUSSION

Trismus causes damage to usual activities such as eating, swallowing, talking, and performing oral hygiene, causing great discomfort to patients. It can be measured both objectively and subjectively, and the subjective measurement of quality-of-life is important to evaluate new treatment technologies.

The use of quality-of-life questionnaires enables the evaluation of the success of a given treatment, especially in patients with chronic diseases. Its translation plays an important role in promoting health knowledge to populations in different countries.

The administration of an assessment instrument validated in another language should allow comparison between different populations, countries, or cultures. Simply translating them does not ensure reliable results because it does not provide sufficient parameters to evaluate whether the results between two samples actually differ or whether they are different owing to translation errors.

Thus, all the steps proposed in the methodology here described, including back translation, must be followed.

CONCLUSION

The Portuguese version of the GTQ is a valid and reliable instrument for the evaluation of patients with limited mouth opening.