Introduction
According to population studies from various countries, the prevalence of chronic tinnitus ranges between 7.6% and 20.1% for people under the age of 50 [1]. Tinnitus treatment remains challenging as the underlying causes are often idiopathic. Psychoacoustic or questionnaire-based evaluation can be used. While psychoacoustic measurements quantify tinnitus, they do not reflect the impact of tinnitus on a person’s life. Individuals with loud tinnitus, for example, who adapt to the sensation of sound, may not experience significant interference with daily living activities and social well-being. Questionnaire-based evaluations are symptom-specific; they highlight the areas of life where tinnitus has an impact and aid in treatment planning. For example, if a person’s sleep is disrupted by loud tinnitus, sound therapy could be an effective treatment option. Tinnitus maskers may also be considered if an individual requires tinnitus relief in a specific situation, such as reading in a quiet room. Treatment and counseling are based on an understanding of the specific effects of tinnitus on the individual.
Tinnitus Handicap Questionnaire (THQ) [2], Tinnitus Reaction Questionnaire (TRQ) [3], Tinnitus Severity Scale [4], Tinnitus Handicap or Support Scale [5], and the Tinnitus Handicap Inventory (THI) [6] are some of the popular self-rating questionnaires used to obtain tinnitus severity ratings. Despite having three or more factors or categories, these questionnaires are limited by unidimensionality in the sense that “impairment leads to disability, disability leads to handicap.” However, there is a push to adopt a more multidimensional paradigm based on the World Health Organization’s (WHO’s) International Classification of Functioning, Disability and Health (ICF) (2001). Aside from being multidimensional, using a universal standard to assess tinnitus improves the consistency of measuring the impact of tinnitus and the outcome of tinnitus treatment across different clinics that provide such services [7].
WHO developed the ICF framework in 2001 as part of the process of revising the International Classification of Impairments, Disabilities, and Handicaps (ICIDH) [8]. This new classification was conceived as a multi-dimensional model in which the impact of health condition on functioning is investigated. The functioning perspective is important to the health care seeker because these are indicators of treatment outcomes [9]. The ICF classification is divided into two sections: functioning and disability, and contextual factors. These two sections are further subdivided into four components: body function and structure, activities and participation, environmental factors, and personal factors (not classified). Each of these components is further classified into chapters (1st level) and categories (2nd to 4th level), with increasing specificity of description. It gives the user the ability to select the level of specificity required to describe the health condition under investigation [9].
It is acknowledged that the ICF, as an exhaustive classification, cannot be used directly as a clinical tool. Furthermore, not all ICF categories are required to describe a specific health condition. As a result, experts recommend developing core sets comprised of the most relevant ICF categories for specific health conditions. ICF core sets have been developed by groups of experts from around the world in 34 areas [10] including hearing loss [11–13] by groups of experts from different parts of the world. There are also generic and rehabilitative core sets that can be used as templates, with the emphasis on body function, activities, and participation [13].
Tinnitus questionnaires, due to their lack of distinctiveness, are frequently not sensitive to treatment-related changes [14]. The Tinnitus Functional Index (TFI) [15,16] is a 25-item questionnaire designed to be a robust tool that responds to treatment-related changes. This tool, however, contains some overlapping items related to emotional function. For example, anxious/worried, bothered/upset, and depressed are three distinct items, while concentrate and focus attention are two distinct items. However, such fine distinctions are difficult to perceive for a layperson, and thus are likely to affect overall scores. Furthermore, the tool’s scoring is time-consuming.
ICF was used to conceptualize tinnitus and its related problems, hypothesizing that 100% of people with permanent tinnitus have impaired body function [17]. Furthermore, for those with clinically significant tinnitus, the associated problems have an impact on their activities and participation. Some researchers mapped the existing tools to ICF and examined the extent of fit to the ICF framework. The TFI and Tinnitus Questionnaire (TQ) items were mapped to ICF and it was found that both tools predominantly had items pertaining to mental functions under body functions [18]. Previously, THI items were also mapped to ICF, and was found that 20 of 25 THI items could be mapped to body function, while the remaining 5 could be mapped to activities and participation [19]. In one study, open-ended responses were mapped to ICF [20] and found responses were primarily related to body function.
As a result, there is a need for a standardized, universal framework to report the impact of tinnitus such that relevant items are included without skewing towards any one domain. Therefore, the purpose of this study was to develop an ICF-based inventory that can measure the impact of tinnitus on an individual, with a specific focus on the components of body function, activities, and participation, in accordance with the rehabilitative core set provided by the ICF Research Branch in 2013. “Body functions” are the physiological functions of body systems, including psychological functions, “activity” is an individual’s execution of a task or action, and “participation” is involvement in a life situation [21].
Subjects and Methods
This study was approved by the relevant institutional ethics committee (IEC-NI/12/OCT/30/55). Informed consent was obtained from all participants prior to their participation in the study.
Development of ICF-Tinnitus Inventory (ICF-TINI)
To ensure thoroughness, efforts were made to replicate as many elements of the ICF core set development process [10]. One audiologist with ICF application and tinnitus rehabilitation experience reviewed the items in each chapter of ICF to eliminate those that were deemed irrelevant to the condition of tinnitus. Mental functions, sensory functions, and pain were chosen from the eight chapters of body function, and learning and applying knowledge, general tasks and demands, and community, social, and civic life were chosen from the nine chapters of activities and participation.
Two audiologists and two otolaryngologists reviewed the selected chapters to identify categories that could potentially describe the impact of tinnitus. This exercise yielded 13 items from body function and 10 items from activities and participation. All body function items were from the third level, five activities and participation items were from the second level, and five other items were from the third level classification of categories (Table 1). These items were written as neutral statements, with definitions provided for some of them.
The same two audiologists and otolaryngologists content validated the 23 neutral statements based on ICF items. With regard to the condition of tinnitus, they rated each item as appropriate, appropriate with modifications, or inappropriate. The items that received 75% agreement from the four judges were included in the inventory. Items rated “appropriate with modifications” by three out of four judges were changed in accordance with the suggestions. Judges were consulted for final approval of the modified items, and the ICF-TINI was created with 15 items as a result (Table 1).
These items were rated using the ICF classification’s universal qualifiers. The first qualifier was used to denote the range of functioning in both body function and activities and participation. In the rating, 0 is “no problem,” 1 is “mild problem,” 2 is “moderate problem,” 3 is “severe problem,” and 4 is “complete problem.” In accordance with the ICF qualifiers, a “not applicable” option, corresponding to the 0.9 qualifier in ICF, was also provided.
As a result, the lowest possible score is 0 and the highest possible score is 60. A score of 60 was assigned to a 100% problem, and the intervals for each qualifier were calculated using this as a reference. Supplementary Material 1 (in the on-line-only Data Supplement) contains the final inventory, as well as the rating scale and ICF codes for each item.
Because Tamil is the local language, it was felt necessary to translate the inventory into Tamil. The ICF-TINI was independently translated into Tamil by two native speakers, and a third person rated the translation’s appropriateness. A linguist then back-translated the combined version. Ten randomly selected undergraduates and graduates rated the tool based on the context’s understandability. Items deemed understandable by 75% of raters were included in the tool, while items deemed not understandable were reworded. The modified tool was then tested for face validity on 10 people. They provided feedback on understandability. The Tamil version of the ICF-TINI was finalized based on their feedback (Supplementary Material 2 in the online-only Data Supplement).
Participants
Individuals over the age of 18 years with unilateral or bilateral chronic tinnitus for at least 3 months, with or without hearing impairment, were eligible for the study. Tinnitus may be a transient condition in people who have acute middle ear infections, neurological disorders, vestibular symptoms, or psychological disorders. All subjects were individuals who had their hearing tested at the Audiology clinic of a tertiary care private hospital in Chennai city.
During their wait time after the case history was taken and before the audiological testing began, all participants completed the inventory with paper and pen. Inventory was given to some participants while they waited for their audiological reports.
Statistical analysis
Cronbach’s alpha was used to assess the tool’s internal consistency reliability. SPSS Amos 20.0 software (IBM Corp., Armonk, NY, USA) was used to perform confirmatory factor analyses (CFA). Because items were drawn from the two components of ICF, CFA was used to determine whether the data obtained from ICF-TINI belonged to a two factor structure (body function and activities and participation). To assess model fit, the root mean square error (RMSEA), chi-square statistics, comparative fit index (CFI), incremental fit index (IFI), and Tucker-Lewis index (TLI) were used.
Results
The ICF-TINI was administered to 137 people (89 males and 48 females). The participants’ average age was 40 years (range: 18 to 70 years). Approximately 80% of the participants were employed adults, with the remaining 20% being geriatric participants who were either unemployed or working part-time. All participants had tinnitus for at least three months and had it either constantly or for the majority of the day. Tinnitus was most commonly described as buzzing (58%) followed by whistling (29%), with a small proportion (13%) describing their tinnitus as ringing, machine noise, or wind noise like. None of the participants had central or objective tinnitus, which was confirmed by tinnitus masking ability.
Internal consistency reliability
The ICF-TINI alpha coefficient was 0.93, indicating that the items have relatively high internal consistency. The item-wise correlation coefficient (Table 2) indicates a moderate to strong correlation. Cronbach’s alpha was 0.87 for body function (6 items) and 0.90 for activities and participation (9 items).
Confirmatory factor analysis
Fig. 1 depicts the factor loading values obtained from the confirmatory factor analysis. The B and D in circles indicate the components of body function (B) and activities and participation (D), and they are linked to the items belonging to these components from the ICF-TINI, and are indicated in the boxes (b1400–b1342, d3503–d163). The arrows pointing from the circle to the boxes indicate the extent the component loads the item (factor loading). The double-headed arrows between B and D indicate the correlation between the two components. The e1–e15 indicate the measurement errors.
Since the factor loading values were all greater than 0.5, no ICF-TINI item was eliminated. Table 3 shows the fit indices, fit values, and suggested criteria. The obtained fit values for RMSEA, CFI, chi-square (df), IFI, and TLI meet the suggested criteria. As a result, the ICF-two-factor TINI’s structure was confirmed.
Discussion
The ICF-TINI was developed using the same process as the core set protocol [11] which included a systematic literature review, expert opinion, and data collection using a convenient sample in a cross-sectional design. While the standard protocol is to use a Delphi technique for the expert survey, a smaller group of judges was used in this study to assess the tool’s content.
The ICF-TINI contains 15 items, 6 of which are components of body function and 9 of which are activities and participation. In total, four items were from the second level categories and 11 from the third level categories. According to WHO in 2001, in real-world ICF applications, 3 to 18 codes are sufficient to describe a condition with two-level precision [22].
ICF was used to study the impact of tinnitus by mapping 25 items from THI and 5 additional items from activities and participation that were not previously covered in THI were added [19]. This 30-item tool contains more body function items, and several of these items are related to the same domain. For example, 9 items are associated with the code b152, b1522 (emotional function), and 6 items are associated with the code b1609 (function). The ICF-TINI and this tool (THI+ICF) share 10 common codes (4 in body function and 6 in activities and participation), but the ICF-TINI items are neutral, as defined in the ICF framework. Neutral items are likely to promote unbiased responses based on an individual’s experience.
Item b240 from the ICF framework, which describes tinnitus, was not included because the ICF-TINI was designed for people who already had tinnitus. Similarly, experts excluded d230, which pertains to hearing function, as these items were deemed inappropriate to the specific condition of tinnitus, but relevant only when hearing loss co-exists. As a result, while the ICF-TINI inventory was designed for people with tinnitus, both with and without co-existing hearing loss, the items in the tool only assess the impact of tinnitus.
The inventory scoring is adapted from the universal qualifiers, ensuring consistency in reporting outcomes. Furthermore, the fact that ICF items are culture-free adds to this inventory’s strength, as these items can be used anywhere in the world. For example, an item such as d163 Thinking, which is described in ICF-TINI as meditating/praying, may be retained as thinking if it is not appropriate for a specific region, as the ICF framework allows for such flexibility.
The internal consistency reliability of ICF-TINI was high comparable to THI [6] and TCQ [23]. Some tools such as TFI [16] and TRQ [3] have higher reliability. However, extremely high values (≥0.95) are undesirable because they indicate that the tool’s items may be redundant [24]. This is also evident from the earlier mapping exercise that showed that several items of the THI belonged to the same domain in ICF framework [19]. However, each item of the ICF-TINI contributes to some unique information without redundancy.
Previously, the strengths and weaknesses of various tinnitus self-assessment questionnaires were evaluated [25]. When compared to the ICF framework, the THQ [2] despite having three factors; physical/social, interference with hearing, and patient’s view of tinnitus, focuses on the component of “body function.” The TRQ [3] primarily assesses psychological stress, which falls under body function and, more specifically, mental function in the ICF framework. The items in the emotional and catastrophic subscales of the THI [6] pertain to the component of body functions, whereas the functional subscale has some items that assess activity limitation and participation restriction, but it also includes items that pertain to body function. Such a focus on a single concept can result in a higher score. The distinctness of THI subscales has previously been questioned [26].
The ICF-TINI confirmatory factor analysis indicates that the scale items are well-fitting, and the fit indices confirm the presence of two structures (body function and activities and participation) in this tool. There are no overlapping items in the tool, and each item evaluates a distinct aspect. The scoring is straightforward and adheres to the ICF qualifiers, meeting the need for a consistent reporting standard.
Therefore, the ICF-TINI is a reliable and valid tool for assessing the impact of tinnitus on an individual’s body function, activities, and participation.
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