Abstract
Background The Facial Disability Index (FDI) is widely used for self-assessment of functional impairment and quality of life in patients with facial palsy.
Objective The study aim was to complete the validation of the FDI by generating an Italian version (IT-FDI) and evaluating its clinimetric properties.
Design This was a longitudinal, observational measurement study.
Methods The questionnaire was translated, cross-culturally adapted, and administered to 100 consecutive participants (outpatients) with facial palsy. The clinical severity of facial palsy, impairments in physical and social function, and quality of life were evaluated with the Sunnybrook Facial Grading System, IT-FDI, and 12-Item Short-Form Health Survey.
Results The IT-FDI showed excellent test-retest reliability for every item and for total scores (intraclass correlation coefficients of .93 and .84 for physical function subscale and social/well-being function subscale, respectively). The IT-FDI confirmed the high internal consistency of the original version, with theta coefficients of .82 for the physical function subscale and .78 for the social/well-being function subscale. The physical function subscale correlated with the Sunnybrook Facial Grading System composite score (r=.44), and the social/well-being function subscale correlated with the 12-Item Short-Form Health Survey mental component (r=.55). The IT-FDI confirmed the good responsiveness of the original version, as expressed by effect size, standardized response mean, and responsiveness ratio of, respectively, 1, 1.03, and 1.21 for the physical function subscale and 0.75, 0.83, and 1.15 for the social/well-being function subscale.
Limitations Responsiveness was evaluated with a limited number of participants.
Conclusions The results demonstrated the test-retest reliability for all items of the FDI and confirmed its internal consistency, construct validity, and responsiveness with an independent and larger clinical subset. This study completes the validation of the FDI and provides the first validated questionnaire in Italian for assessment of disability and quality of life specifically in patients with facial palsy.
Facial palsy is the most frequent affliction of cranial nerves and may result in a wide range of functional limitations, such as difficulties in eating, drinking, speaking, and ocular problems.1 Furthermore, the injury of cranial nerve VII leads to static and dynamic facial asymmetry and possibly aberrant synkinesis,2 with negative consequences for self-perception, emotional communication, and social interaction.3 Functional limitations, combined with facial disfigurement, may limit participation in activities and adversely affect quality of life, leading to anxiety, depression, and social isolation, particularly when recovery from facial palsy is not rapid.4 Therefore, proper assessment and monitoring of people with facial palsy should include an evaluation of disability and quality of life.5
To this aim, several systems for the subjective evaluation of functional limitations and quality of life specifically in people with facial paralysis were proposed (reviewed by Ho et al6). In 1996, VanSwearingen and Brach introduced the Facial Disability Index (FDI), a 10-item questionnaire aimed at evaluating the subjective perception of functional limitations and social participation in people with facial palsy.7 This questionnaire showed high internal consistency, good construct validity, and responsiveness7,8 and since then has been widely used.9–12 Recently, some measurement properties were confirmed by other authors through the use of Spanish and Swedish versions of the questionnaire.13,14 Furthermore, the good test-retest reliability for the physical function and social/well-being function total scores of the Swedish version of the FDI has been reported,14 but the test-retest reliability for each item still needs to be determined.6
The aims of this study were: (1) to complete the validation of the FDI and (2) to confirm the previously assessed measurement properties with an independent and larger number of participants who had facial palsy. To this end, we generated an Italian version of the FDI (IT-FDI), linguistically faithful to the original and culturally adapted, and evaluated its measurement properties in participants who were native Italian speakers and had a facial palsy.
Method
Facial Disability Index
The FDI is a 10-item questionnaire with 2 subscale scores: 5 items contribute to the physical function subscale, and 5 items contribute to the social/well-being function subscale. The physical function subscale investigates problems in eating, drinking, speaking, lacrimation, and oral hygiene. The social/well-being function subscale investigates subjective perception of anxiety, irritation, and isolation; problems in sleeping; and limitations in social participation. Each item is rated on a 6-point scale, ranging from severe disability to absence of disability. Both subscales are transformed to a score on a 100-point scale, with 100 indicating unimpaired physical or social/well-being function. All questions refer to the preceding month.7
Translation and Cultural Adaptation
The IT-FDI was created by a multidisciplinary committee, in agreement with international guidelines for translation and cross-cultural adaptation of outcome measures.15,16 The original version of the questionnaire was translated into Italian separately by 2 Italian physicians who are fluent in English and have experience with patients who have facial palsy. The 2 versions were compared by a committee composed of 3 physicians who had experience in the treatment of patients with facial paralysis, and a third, consensus version of the scale was produced. This scale was back-translated into English by a translator who was a native English speaker and had experience with scientific translation. Finally, a committee of 6 physicians who have various backgrounds and experience with patients who had facial palsy, together with the translator, compared the original scale, the individual and consensus translations, and the back-translation by examining semantic correspondence and cultural appropriateness and produced the final version of the IT-FDI.
Validation Study
Sample size estimation.
The internal consistency, construct validity, and floor and ceiling effects of the scale were evaluated with a sample of 100 consecutive participants. A sample of 100 participants, each responding to the 10-item questionnaire, achieved 90% power to detect the difference between the theta coefficient under the null hypothesis of .8 and the theta coefficient under the alternative hypothesis of .875 by use of a 2-sided F test with a significance level of .05. Test-retest reliability was evaluated with a subset of 37 consecutive participants. A sample size of 37 produced a 2-sided 95% confidence interval with a width equal to .25 when the sample correlation was .8. Responsiveness was evaluated with a subset of 41 participants, including all of those who received the first rehabilitative treatment at the Rehabilitation Unit of the University Hospital San Matteo, Pavia, Italy, and underwent the first posttreatment visit at least 1 month after the first clinical assessment. These criteria were chosen to avoid temporal overlapping between the first and the second evaluations because the questions in the IT-FDI refer to the preceding month.
Participants.
We enrolled in the study 100 consecutive participants (outpatients) who had unilateral facial palsy evaluated at the Rehabilitation Unit of the University Hospital San Matteo beginning in January 2011 and were able to read and understand the questionnaire. Figure 1 summarizes the inclusion criteria and the samples used to assess the various properties of the scale. All procedures conformed to the standards established by the Declaration of Helsinki, and all participants gave their written informed consent to participate in the research study.
Inclusion criteria and samples used for validation of the Italian version of the Facial Disability Index (IT-FDI). SFGS=Sunnybrook Facial Grading System, SF-12=12-Item Short Form Health Survey.
Procedure.
Before each clinical evaluation, all participants were asked to complete the IT-FDI and the Italian version of the 12-Item Short-Form Health Survey (SF-12).17 After completing both questionnaires, the participants were asked whether any part of the IT-FDI was difficult to understand. The same physician, who had extensive experience with patients who had facial palsy, graded the severity of the clinical condition for all participants using the Italian version of the Sunnybrook Facial Grading System18 (SFGS) and assessed the level of comorbidity using the adjusted Charlson Comorbidity Index.19 The test-retest reliability for the IT-FDI was evaluated by asking a subset of 37 consecutive participants to complete the IT-FDI again at the end of the visit.
Outcome measures.
The Italian version of the SFGS is a scale used to assess the severity of facial palsy.18,20 The scale provides a clinical composite score ranging from 0, for complete facial paralysis, to 100, for normal facial function, by evaluating symmetry at rest and during voluntary movements as well as the severity of synkinesis. The Italian version of the SF-12 is a questionnaire used to globally assess health status.17 It defines 8 domains of health (physical functioning, limitations due to physical health, body pain, general health perceptions, vitality, social functioning, limitations due to emotional status, and mental health) and provides summary measures of physical health and mental health (the physical component summary and the mental component summary). The means for the Italian general population are 51.2 (SD=7.4) and 47.8 (SD=10.1), respectively.17 The age-adjusted Charlson Comorbidity Index was used to combine age and comorbidities to estimate relative risk of death and long-term survival.19,21 Generally, a combined score for age and comorbidity of ≥5 represents the expression of a severe clinical condition.21
Data analysis.
Data were described as the mean (standard deviation) if continuous and as counts (percentages) if categorical. Internal consistency for the physical function and social/well-being function subscales was assessed with the theta coefficient by use of principal components factor analysis (PCFA), as described by Armor22; the values ranged from 0 to 1, with 1 indicating perfect reliability. In PCFA, a participant's score on any item is broken down into numerous factors; the contribution of each item to a given factor determines the weighting of the item for that factor. Thus, each factor explains a certain amount of the variance of the construct being measured and represents a statistically independent, differential contribution of a set of individual items to the construct. In PCFA, the amount of variance accounted for by a particular factor is known as the latent root. The formula used in the present study for theta reliability was: [p/(p−l)][(L−1)/L], where p is the number of items in the scale and L is the latent root of the factor representing the component loadings of the subscale (functional or social, in this case) items of the PCFA.
Item-total correlation was evaluated with the theta coefficient and was considered to be acceptable when the value was ≥.70. Test-retest reliability was evaluated with the 1-way random-effects analysis of variance intraclass correlation coefficient and 95% confidence interval. The intraclass correlation coefficient was evaluated as follows: poor for values of less than .40, moderate to good for values of .40 to .74, and excellent for values of greater than .75.23 Normality was assessed with the Kolmogorov-Smirnov test.
Construct validity was investigated by assessing the relationship between IT-FDI scores (physical function and social/well-being function subscales) and other outcome measures (the composite score of the SFGS and the physical and mental domains of the SF-12). Spearman nonparametric correlation coefficients (r values) were calculated. The magnitude of an effect size for correlation coefficients was evaluated as follows, as described by Cohen: small for correlation coefficients on the order of .1, medium for those on the order of .3, and large for those on the order of .5.24 In our study, we considered a correlation coefficient of greater than .3 significant, in line with many correlation coefficients reported in the literature.25 Floor and ceiling effects were considered to be present if more than 15% of the participants displayed the worst or the best possible scores, respectively.26
For the assessment of responsiveness, the indicator for improved status was derived from the baseline standard deviation of the SFGS composite score for the entire sample (SD=23) multiplied by .2 and .5, which were indicators of small and moderate/substantial effect size changes, respectively; increases in the SFGS composite score between the first visit and the second visit of 4.6 and 11.5 points were used as cutoff values for small and moderate/substantial improvements, respectively.27,28 As measures of responsiveness, the effect size,29 the standardized response mean (SRM),30 and the Guyatt responsiveness ratio (GRR)31 were calculated.
The effect size was calculated as the ratio between the mean change score (ie, the mean difference between follow-up scores and baseline scores) and the standard deviation of the baseline scores.29 The SRM was calculated as the ratio between the mean change score and the standard deviation of the change scores.30 The effect size and SRM values were evaluated as follows: small for values of less than 0.2, moderate for values of 0.21 to 0.50, large for values of 0.51 to 0.8, and very large for values of greater than 0.8.
The GRR was calculated as the ratio between the mean change score on the physical function or social/well-being function subscale for participants identified as showing improvements and the standard deviation of the mean change score for participants identified as showing no change.31 If the GRR is larger than 1, then the mean change score in participants showing improvements exceeds the measurement error, and the instrument may be considered to be responsive to an extent that is proportional to the magnitude of the responsiveness ratio.31
The mean change scores in participants showing no improvement, small improvements, and moderate or substantial improvements were compared by use of an analysis of variance. Two-sided P values of less than .05 were considered statistically significant. Stata 12.0 (StataCorp 2012, College Station, Texas) was used for all computations.
Role of the Funding Source
Dr Pavese is partially supported by an Investigator Fellowship from Collegio Ghislieri, Pavia, Italy.
Results
Translation and Cultural Adaptation
The procedures of translation and cultural adaptation were conducted without difficulties, and the final version of the scale was found to be faithful to the original and culturally adapted for people who are Italian (Appendix).
Validation Procedure
Population and acceptability.
The validation procedure was performed with data from 100 participants who had facial palsy of various grades and etiologies. Table 1 summarizes the characteristics of the participants. Most of the participants had chronic facial palsy, but 18% of the participants were evaluated within 3 months of the onset of palsy. All of the participants considered the IT-FDI to be clear and adequate to evaluate their condition. In no case did the completion of the questionnaire require more than 5 minutes, and the level of questionnaire completeness was 100%.
Demographic and Clinical Characteristics of Participantsa
Internal consistency.
The IT-FDI showed good internal consistency, with theta coefficients of .82 for the physical function subscale and .78 for the social/well-being function subscale, based on the latent root of the factor analysis. The latent root of factor 1 (physical function subscale) was 2.90 (32.27%), and that of factor 2 (social/well-being function subscale) was 2.19 (24.35%). The PCFA of the IT-FDI subscale item scores for the sample confirmed that the IT-FDI physical function subscale items formed a homogeneous group, clearly separable from the IT-FDI social/well-being function subscale items (eTable). When each of the 10 items of the scale was excluded one by one, the coefficients ranged from .73 to .80; no single item was found to affect the internal consistency substantially.
Test-retest reliability.
The test-retest reliability for every item as well as for the physical function and social/well-being function total scores was excellent (Tab. 2).
Test-Retest Reliability of Individual Item and Total Scores on the IT-FDI (n=37)a
Construct validity.
Table 3 summarizes the data for construct validity. As expected, the physical function subscale of the IT-FDI showed a medium correlation with the composite score of the SFGS, which measures the severity of palsy, and with the physical component summary of the SF-12, which is a self-reported assessment of physical status. On the other hand, the social/well-being function subscale of the IT-FDI showed a large correlation with the mental component summary of the SF-12, which indicates mental status, and a poor correlation with the parameters indicating physical status. In agreement with the original version,7 the 2 subscales of the IT-FDI showed a weak correlation (r=.34, P=.03).
Construct Validity (N=100)a
Table 4 shows the relationship between individual items of the SFGS (resting and voluntary movement symmetry) and the IT-FDI related to the mouth. Questions 1, 2, and 5 in the IT-FDI, concerning eating, drinking, and oral hygiene, correlated mainly with the score for lip puckering in the SFGS (orbicularis oris muscle), whereas question 3, concerning speaking, was related more to the score for snarling and smiling with an open mouth in the SFGS (levator labii superioris alaeque nasi and zygomaticus-risorius muscles). The fourth question in the IT-FDI, concerning lacrimation, showed a significant correlation with the ability to close the eye (activation of orbicularis oculim muscle in the SFGS; r=.40, P=.0001); no correlation was observed with eye size at rest (r=−.19, P=.06) or with eye synkinesis (r=.05, P=.63).
Correlations of Items Related to Mouth Function in the IT-FDI and the SFGS (N=100)a
Floor and ceiling effects and responsiveness.
Neither a floor effect nor a ceiling effect was observed. Data from 41 participants were used to assess responsiveness. The mean time between the first visit and the second visit was 4.5 months (SD=3.05, range=1–15.2). The treatment performed between the 2 clinical assessments consisted of exercises at home for 27 participants (66%), exercises at the Rehabilitation Unit of the University Hospital San Matteo for 4 participants (10%), and botulinum toxin injection for 10 participants (24%).
Figure 2 shows the clinical evolution between the first visit and the second visit for the 41 participants whose data were used to assess responsiveness. Figure 2A shows the correlations between the change in the IT-FDI physical function subscale score and the change in the SFGS composite score (r=.43, P=.005), Figure 2B shows the correlations between the change in the IT-FDI social/well-being function subscale score and the change in the SFGS composite score (r=.24, P=.13).
Changes in the scores on the Italian version of the Facial Disability Index (IT-FDI) and the Sunnybrook Facial Grading System (SFGS) after treatment. (A) Correlations between the change in the IT-FDI physical function subscale score and the change in the SFGS composite score (n=41). (B) Correlations between the change in the IT-FDI social/well-being function subscale score and the change in the SFGS composite score (n=41). Change was evaluated as the difference between the second visit and the first visit.
For the 31 participants showing a moderate/substantial effect size change in the SFGS, the mean scores on the IT-FDI at the first and last visits were 54 (SD=19) and 72 (SD=18) for the physical function subscale and 60 (SD=26) and 77 (SD=18) for the social/well-being function subscale, respectively. For the 5 participants showing a small effect size change, the mean scores on the IT-FDI at the first and last visits were 74 (SD=29) and 81 (SD=19) for the physical function subscale and 63 (SD=16) and 87 (SD=12) for the social/well-being function subscale, respectively. For the 5 participants classified as not showing improvement, the mean scores on the IT-FDI at the first and last visits were 72 (SD=21) and 72 (SD=21) for the physical function subscale and 69 (SD=17) and 75 (SD=22) for the social/well-being function subscale, respectively. The difference in the mean changes in participants showing no improvement, small improvements, and moderate/substantial improvements was statistically significant (P=.03) for the physical function subscale.
The degree of change expressed by the effect size, SRM, and GRR for participants showing moderate/substantial improvements (n=31) were, respectively, 1, 1.03, and 1.21 for the physical function subscale and 0.75, 0.83, and 1.15 for the social/well-being function subscale, indicating good responsiveness of both subscales of the IT-FDI.
Discussion
The present study provides the first validated questionnaire in Italian for the assessment of disability and quality of life specifically in patients with facial palsy. Furthermore, the results demonstrated the test-retest reliability for each item of the FDI, thereby completing its validation as an appropriate measurement tool. Finally, the results confirmed the good internal consistency, construct validity, and responsiveness of this instrument with an independent and larger clinical subset.
The IT-FDI, together with the recently published Spanish and Swedish versions,13,14 represents the increasing interest in and need to identify a consensus instrument for evaluating disability in patients with facial palsy; studies with these versions of the FDI may encourage its translation into other languages. Such translations could pave the way for urgently needed international multicenter clinical trials to assess the efficacy of various interventions for facial palsy, above all, physical therapy.32
Gonzalez-Cardero et al13 verified the measurement properties of the Spanish version of the FDI in patients with facial palsy after parotidectomy. In the present study, like VanSwearingen and Brach,7 we opted to use a larger number of participants seeking rehabilitation for facial palsy. This approach covered the full spectrum of facial palsy in terms of etiology, clinical status, and severity. Therefore, the results of the present study strengthened the validity of the FDI as an appropriate tool for evaluating facial palsy–related disabilities.
For assessment of the construct validity of the physical function subscale of the FDI, a measure of the clinical severity of facial palsy was required. For the validation study of the original version, VanSwearingen and Brach7 considered the symmetry of voluntary movement, a subscale of the SFGS that evaluates symmetry and muscular excursion during facial movement.20 In the present study, we extended this analysis by considering the composite score of the SFGS and its subscales.18,20 Interestingly, we confirmed the correlation of the physical function subscale of the FDI with the symmetry of voluntary movement of the SFGS and found an even stronger correlation with the composite score of the SFGS (which also includes symmetry at rest and the presence of synkinesis).
Remarkably, we observed correlations of the activities of specific facial muscles, as assessed with the SFGS, and disabilities in related activities, as assessed with the FDI. Problems in eating, drinking, and oral hygiene correlated with difficulties in lip puckering (orbicularis oris muscle), and problems in speaking showed a stronger correlation with difficulties in snarling and smiling (levator labii superioris alaeque nasi and zygomaticus-risorius muscles). Whether the latter correlation is a peculiarity of Italian or can be extended to other languages will have to be investigated.
Overall, our data confirmed and corroborated the construct validity of the FDI for various clinical aspects of facial palsy. Our results confirmed the poor correlation between the physical function and social/well-being function subscales of the FDI reported by VanSwearingen and Brach.7 Those authors also reported a poor correlation between the social/well-being function subscale of the FDI and the severity of facial palsy, as assessed with the SFGS7; that finding was replicated in our series. These data probably explain why the physical function subscale of the FDI showed higher responsiveness to clinical change measured with the SFGS than the social/well-being function subscale. Further studies are needed to investigate the influence of psychosocial factors on the perception of disability and quality of life in patients with facial palsy.
In the present study, we assessed the test-retest reliability of the IT-FDI by asking participants to complete the questionnaire before and after visits. We preferred this method over a telephone recall for obtaining a second assessment under the same conditions (outpatient setting). However, our approach could be regarded as a limitation of the study, and the test-retest reliability of the scale may have been overestimated because of the short time between the 2 compilations; indeed, we could not exclude participants' partial recall of initial ratings.
Another limitation of the present study was that we verified responsiveness only with a limited number of participants after the first cycle of treatment. However, the good responsiveness of the FDI in patients undergoing long-term rehabilitative care has already been demonstrated.8
Recent years have witnessed a flowering of refined surgical interventions and rehabilitation approaches specifically for various facial regions. In this context, functional assessment with the FDI might represent a valid complement to the clinical evaluation of patients with facial palsy and could be instrumental in planning and monitoring a multidisciplinary patient-oriented intervention to restore movement, reduce disability, and improve quality of life.
Appendix.
Italian Version of the Facial Disability Index.
Footnotes
Dr Pavese, Dr Tinelli, and Professor Dalla Toffola provided concept/idea/research design. Dr Pavese, Dr Cecini, Dr Camerino, and Professor Dalla Toffola provided data collection. All authors provided data analysis and writing. Dr Pavese and Professor Dalla Toffola provided project management and institutional liaisons. Professor Dalla Toffola provided fund procurement, participants, and facilities/equipment. The authors thank Charlotte Buckmaster for her linguistic expertise.
Dr Pavese is partially supported by an Investigator Fellowship from Collegio Ghislieri, Pavia, Italy.
- Received June 18, 2013.
- Accepted April 18, 2014.
- © 2014 American Physical Therapy Association
References
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