Cross-cultural adaptation of the Brazilian version of the Vocal Fatigue Index – VFI Equivalência cultural da versão brasileira do Vocal Fatigue Index – VFI

Accepted: March 01, 2016 Study carried out at Speech-Language Pathology and Audiology Department of the “Universidade Federal de São Paulo” – UNIFESP São Paulo (SP), Brazil. 1 Universidade Federal de São Paulo – UNIFESP São Paulo (SP), Brazil. 2 Centro de Estudos da Voz – CEV São Paulo (SP), Brazil. 3 Sindicato dos Professores de São Paulo – SINPRO-SP São Paulo (SP), Brazil. 4 East Tennessee State University Johnson City (TN), United States of America. Financial support: “Coordenação de Aperfeiçoamento de Pessoal de Nível Superior” CAPES. Conflict of interests: nothing to declare. ABSTRACT


INTRODUCTION
Vocal fatigue is an individual perception manifested by increased vocal effort associated with increased vocal demands, which improves with voice rest (1) . Vocal fatigue is also described as a symptom of vocal change or when associated with negative behaviors, as the cause of dysphonia (2) . Frequently, presence of vocal fatigue is assessed by the presence of a variety of symptoms (3)(4)(5) .Various definitions of vocal fatigue exist in the literature resulting in increased difficulty to accurately assess vocal fatigue from the patient perspective (6,7) .
Recently, an American group of researchers developed and validated the Vocal Fatigue Index -VFI (7) , a tool that assists in the reliable identification of individuals with vocal fatigue. The American English protocol has 19 questions divided into three domains: tiredness of the voice and voice avoidance, physical discomfort associated with voicing, and improvement of symptoms with rest or lack thereof (7) .
According to the international Scientific Advisory Committee of Medical Outcomes Trust standards (8) , any instrument must be validated to be used in another language and culture. The first step for this validation is the cultural and linguistic adaptation, thus, language, cultural and social differences that might exist for the application of the instrument in the new culture and language are addressed.
Therefore, the aim of this study was to perform the cultural equivalence of the VFI for Brazilian Portuguese by its cultural and linguistic adaptation.

METHODS
This prospective research was approved by the Research Ethics Committee of the "Universidade Federal Sao Paulo" -UNIFESP (CAAE: 09205412.1.0000.5505 under the protocol number 159.968, date: 29.11.2012). All study participants agreed to participate and signed an Informed Consent Form.
The VFI (7) was translated into Brazilian Portuguese by two Brazilian bilingual speech-language pathologists (Translator 1 -T1 and Translator 2 -T2), who conducted the conceptual translation. The translations were analyzed and compared by a committee of five speech-language pathologists specialized in voice with proficiency in English. Differences were discussed and, if necessary, modifications were made, resulting in the final translated version (Portuguese version -PV).
A third Brazilian bilingual speech-language pathologist, who did not participate in the previous steps, back-translated the final version into English. This version was compared to the original English version of the protocol resulting in the Portuguese version with semantic and language adaptation. Any conceptual differences were again discussed by the researchers and by the same committee who participated in the previous step, resulting in the final version with cultural and linguistic equivalence of the VFI.
The final version in Portuguese, as well as the original version in English, are completed on a categorical scale according to frequency of occurrence of symptoms: 0 = never, 1 = almost never, 2 = sometimes, 3 = almost always, and 4 = always. For the cultural equivalence of the Portuguese version, the option "not applicable" was added to the categorical scale and 20 individuals with vocal complaints and dysphonia were asked to complete the Portuguese version of the VFI. The questions considered as "not applicable" were disregarded from the Brazilian version.
Inclusion criteria for the 20 individuals were presence of vocal complaints and any type, degree and etiology of dysphonia. Exclusion criteria were use of medications for psychiatric diseases and/or presenting any neurological disorder that prevented the understanding of the questionnaire.

RESULTS
The Brazilian Portuguese version of VFI was entitled "Índice de Fadiga Vocal -IFV". The participants did not choose "not applicable" for any of the questions and hence no question had to be eliminated or modified in the linguistic and cultural adaptation. The translation protocol and cultural adaptation process are found in Chart 1.
As in the original VFI, the translated version has 19 questions divided into three domains: the first consists of eleven items related to tiredness of the voice and voice avoidance; the second has five items about physical discomfort associated with voicing, and the third has three items regarding improvement of symptoms with rest or lack thereof (Appendix A).

DISCUSSION
Vocal fatigue is a current topic with relevance to research on dysphonic individuals or at risk populations (3)(4)(5) . Few studies have developed specific instruments for self-assessment of vocal fatigue, and none has been developed or validated for Brazilian Portuguese, which makes the cultural and linguistic adaptation necessary as the first step for the validation of such instrument (8) .
The cultural and linguistic adaptation aims to adjust the items of an instrument for its use for the population in concern; therefore, any sociocultural differences between cultures and languages are solved. It is important to highlight that this is not a literal translation of the original instrument (8) , thus, it can be used in individuals from the target culture. Such methodology of cultural adaptation has been utilized for the translation and validation of other Brazilian Portuguese instruments of the speech language pathology field (9)(10)(11)(12)(13)(14)(15) .
With the completion of translation and adaptation for Brazilian Portuguese, the "IFV" validation process was initiated. The aim of the validation is to demonstrate the psychometric properties of validity, reliability, and sensitivity of the Brazilian version, which enables its reliable use for research and clinical practice (8) . Future research with the "IFV" can compare vocal fatigue aspects of dysphonic individuals with other self-assessment instruments, or include vocal fatigue characteristics as a multidimensional evaluation item for at risk groups.

CONCLUSION
The Brazilian Portuguese version of the instrument, "Índice de Fadiga Vocal -IFV", presents cultural and linguistic equivalence to its original version, Vocal Fatigue Index -VFI. The validation of the VFI for Brazilian Portuguese is ongoing.