Discussion
In this study, the TFI has been translated into Spanish and validated
for clinical practice. To the best of our knowledge, this is the first
study designed to perform a translation from English to Spanish,
cross-cultural adaptation and validation of the TFI for use in Spain.
Given the psychological impact of tinnitus and the extent to which it
may impair patients’ quality of life, validated disease-specific
questionnaires are essential for the comprehensive assessment of this
population. As we have mentioned previously, the TFI, developed by
Meikle et al. in 2012, provides a reliable and valid measurement of the
multiple domains of tinnitus severity and intervention
outcomes.[5] The scientific literature describes other
questionnaires such as the THI and VAS that may be used to assess the
emotional and functional impact or loudness of
tinnitus.[22] Nonetheless, the TFI has some major
advantages such as its comprehensive coverage of many important
tinnitus-related complaints, as well as the sum of its subscale scores
providing a reliable categorization of tinnitus severity and allowing
assessment of responsiveness to treatment.[9] To date, TFI
has been translated, adapted and validated versions in numerous
languages, including German, English, Swedish, Italian, and Mandarin
Chinese.[8,9,10,23,24]
The present study found the Sp-TFI had a high overall internal
consistency (Cronbach’s α of 0.83), lower than that of the original
version (α of 0.97), and the aforementioned Chinese (α of 0.969),
Swedish (α of 0.93) and Italian (α between 0.92 and 0.96) versions, but
higher than that found in the UK (α of 0.80). Analyzing subscales
separately, we found a relatively low internal consistency in the
Intrusiveness and Auditory subscales (0.68 and 0.65, respectively).
Given that both values are near the threshold considered to indicate
acceptable internal consistency (0.7) and the moderate sample size, we
might attribute these lower values to the mood of patients on the day
the questionnaire was completed. Indeed, low internal consistency was
not observed in the Swedish version,[10] but the UK
analysis of the English version found an even lower value for
Intrusiveness (α of 0.58).[9] Hence, we consider that
further research should be carried out to explore the properties of the
Intrusiveness subscale.
The temporal stability of the measurements was assessed using the
ICC(2,1). Considering the 95% confidence interval of the ICC estimate,
values greater than 0.90 are indicative of excellent reliability.
Notably, we found an ICC(2,1) of 1 (CI: 0.99 – 1), indicating great
test-retest reliability, even higher than values found for the original
version (ICC = 0.78), for the German version (ICC = 0.91), for the
Swedish version (ICC = 0.93) ).[5,8,10] and in the UK
analysis of the original version (ICC = 0.91).[9] The
reason for this could be that we allowed only 2 weeks between the test
and retest, while Meikle et al. waited 3 months, though similarly short
intervals were used to assess the other translations (between 1 and 3
weeks). Analyzing the subscales of the Sp-TFI, all the scores also had
excellent reliability.
The Sp-TFI’s convergent validity with the THI was high (r=0.71, p
< 0.01) and comparable to that found for the Chinese, Swedish,
and Italian versions and UK analysis of the English version (r=0.86,
0.8, 0.77 and 0.75, respectively).
The evaluation of each predictive variable showed direct correlations of
the THI with sex, PTA, Sp-TFI overall score, and Sp-TFI SL and R
subscale scores. Meanwhile, an indirect correlation was found between
the THI and Sp-TFI A subscale scores. Notably, the Sp-TFI A subscale
obtained a low Cronbach’s α (α=0.65), while in analysis of the Swedish
and Italian versions, the authors also observed a weaker correlation for
this Auditory subscale than the other seven subscales (r=0.52 and
α=0.35, respectively).
The main strength of this study is that the translation, cross-cultural
adaptation, and validation of the Sp-TFI was carried out following the
highest standards for translation of self-assessment
questionnaires.[12] Strong validity was achieved with
internal consistency higher than 0.8, comparable to results obtained for
the original English and translated versions.
The main limitation of the study is that most of the authors and
translators involved in this work were Spanish. For this reason, we
believe that further research is necessary to assess whether linguistic
and/or cultural modifications are required to adapt it for use in other
Spanish-speaking countries. Moreover, despite the good results, the
small sample size could lead to bias and may limit the reliability and
validity of the results. Therefore, a larger sample should be recruited
and used for further validation. Finally, our study suggests that the
Sp-TFI is a suitable instrument for measuring the impact of tinnitus
among Spanish speakers in Spain. The reliability and validity of this
version seem to be very good and comparable to the original version of
the TFI and indicate it can be used to assess tinnitus in clinical
practice.