|Year : 2000 | Volume
| Issue : 1 | Page : 65-70
Adaptation of WHOQOL as health-related quality of life instrument to develop a vision-specific instrument.
R Dandona, L Dandona, CA McCarty, GN Rao
Public Health Ophthalmology Service and International Centre for Advancement of Rural Eye Care, L.V. Prasad Eye Institute, L.V. Prasad Marg, Banjara Hills, Hyderabad-500 034, India
Public Health Ophthalmology Service and International Centre for Advancement of Rural Eye Care, L.V. Prasad Eye Institute, L.V. Prasad Marg, Banjara Hills, Hyderabad-500 034
Source of Support: None, Conflict of Interest: None
The WHOQOL instrument was adapted as a health-related QOL instrument for a population-based epidemiologic study of eye diseases in southern India, the Andhra Pradesh Eye Disease Study (APEDS). A follow-up question was added to each item in WHOQOL to determine whether the decrease in QOL was due to any health reasons including eye-related reasons. Modifications in WHOQOL and translation in local language were done through the use of the focus groups including health professionals and people not related to health care. The modified instrument has 28 items across 6 domains of the WHOQOL and was translated into the local language, Telugu, using the pragmatic approach. It takes 10-20 minutes to be administered by a trained interviewer. Reliability was within acceptable range. This health-related QOL instrument is being used in the population-based study APEDS to develop a vision-specific QOL instrument which could potentially be used to assess the impact of visual impairment on QOL across different cultures and for use in evaluating eye-care interventions. This health-related QOL instrument could also be used to develop other disease-specific instruments as it allows assessment of the extent to which various aspects of QOL are affected by a variety of health problems.
Keywords: Adult, Aged, Comparative Study, Eye Diseases, epidemiology, psychology, Female, Health Status Indicators, Humans, Incidence,
|How to cite this article:|
Dandona R, Dandona L, McCarty C A, Rao G N. Adaptation of WHOQOL as health-related quality of life instrument to develop a vision-specific instrument. Indian J Ophthalmol 2000;48:65-70
|How to cite this URL:|
Dandona R, Dandona L, McCarty C A, Rao G N. Adaptation of WHOQOL as health-related quality of life instrument to develop a vision-specific instrument. Indian J Ophthalmol [serial online] 2000 [cited 2020 Apr 1];48:65-70. Available from: http://www.ijo.in/text.asp?2000/48/1/65/14847
Blindness and visual impairment affect almost all aspects of life, but to varying extents, depending on the patient's perception of impairment or disability. The assessment of quality of life (QOL) is of particular importance in assessing the impact of visual impairment on daily life as it can provide a comprehensive picture of the burden of visual impairment that is beyond clinical evaluation as the latter quantifies only the visual loss and not the impact of that loss.
QOL, defined by the World Health Organization (WHO), is "an individual's perception of his/her position in life in the context of the culture and value systems in which he/she lives and in relation to his/her goals, expectations, standards and concerns". Efforts to measure health expectancy have increased with increase in the life expectancy, leading to assessment of 'health-related quality of life' which is patient-based and focuses on the impact of a perceived health state on the ability to live a fulfilling life.
Some instruments developed in the developed world are being used to assess QOL in ophthalmic patients[4-6] but the cross-cultural compatibility of these instruments has not been demonstrated and this makes direct application of these instruments in the developing world difficult. A short instrument has been developed in India to assess vision-related QOL which focuses mainly on functional disability. Our aim was to develop a comprehensive vision-specific QOL instrument suitable for assessing impact of visual impairment on health-related QOL. The World Health Organization QOL instrument (WHOQOL), a generic QOL instrument which has been recently translated into Hindi in north India, was selected. This instrument has not been devised for specific patient groups or diseases, but can be applied to a wide variety of patient groups and healthy populations. We adapted the WHOQOL as a health-related QOL instrument. This paper describes the stages in modification of the WHOQOL to make it a health-related QOL instrument. We are testing this modified WHOQOL in the population-based Andhra Pradesh Eye Disease Study (APEDS) in southern India to identify those aspects of QOL that are affected by visual impairment, so as to develop a vision-specific QOL instrument.
| Materials and Methods|| |
The generic WHOQOL was modified into a health-related QOL instrument for use in APEDS, a population-based epidemiology study of 10,000 people in four areas representative of the Indian state of Andhra Pradesh. Detailed methodology of APEDS is reported elsewhere.
| Stage 1: Selection of the instrument|| |
After reviewing the literature, the WHOQOL was selected as it has been developed simultaneously in 10 countries and thus is potentially cross-cultural. The development process of the WHOQOL is more fully documented elsewhere. [7, 11-13]
| Stage 2: Modifications|
A follow-up question based on expert reviews was developed and added to each item of the WHOQOL to make it a health-related QOL instrument. This followup was used to assess whether the decrease in QOL was due to eye-related problems or other health-related problems. This question was put only to those who reported decrease in QOL. This was an open-ended question wherein the subject was asked to report the possible cause of decrease in QOL and was documented. If the subject reported two or more causes, the most important cause as perceived by the subject was also documented.
| Content|| |
The WHOQOL is organised into six broad domains of QOL, which are: physical, psychological, level of independence, social relationships, environment, and spirituality /religion /personal beliefs. Within each domain there are several sub-domains (facets) which summarise that particular domain. To determine the domains and facets for the health-related QOL instrument, the principal investigator and the study coordinator drafted a provisional list of domains and facets of QOL from the WHOQOL after reviewing the definitions of all the domains and facets. A focus group comprising three medical experts, two public health experts, a sociologist, an anthropologist, and a demographer reviewed the domains and facets of the WHOQOL, and the provisional list was modified. Carefully moderated interviews with a broad range of patients and healthy individuals, who represented the target population demographics in terms of age, gender, and educational and socioeconomic background, were conducted to check the acceptability of the selected domains and facets in the provisional list. Data from these interviews were used to confirm inclusion/exclusion of domains and facets of the WHOQOL selected for the modified instrument.
| Response scale|| |
The WHOQOL has four types of response scales (intensity, capacity, frequency, and evaluation). These response scales are described in detail elsewhere. Each facet has a varying number of questions based on the response scales. The response scales were provisionally listed for each question based on 'how much each response scale was able to elicit the health-related QOL of the respondents in each of the facets.' This was tested in a manner similar to selection of the domains and facets.
| Scoring system|| |
The WHOQOL produces a quality of life profile. It is possible to derive 6 domain scores, 24 individual facet scores, and an overall QOL and general health perceptions score using summative scoring. Each domain contributes equally to the overall QOL score and similarly, each facet contributes equally to the respective domain score because it is likely that people may value the different domains of QOL unequally in evaluating their overall QOL; similarly, the facets within each domain of QOL may be valued differently by individuals in different psychosocial circumstances. The WHOQOL has two types of scoring based on whether the question is positively or negatively framed. We followed the same concept of scoring and tried to simplify it into a unidirectional scoring system.
| Stage 3: Translation|| |
For better understanding and acceptability of the modified instrument, we translated it into Telugu, the local language of the Indian state of Andhra Pradesh, with the aim of maintaining, as far as possible, conceptual, semantic, and technical equivalence between the target language and source language (English) versions of the instrument. The features of the instrument were explained to two translators so that they had a clear and detailed understanding of the instrument, which could then be appropriately translated to match closely the language of the target population. The translated version of the instrument was reviewed by a bilingual panel consisting of individuals skilled in interviewing and assessment, as well as the members of the focus group listed earlier. They checked for any inconsistencies between the source instrument and the translated instrument, with the aim of maintaining the integrity of the translated instrument as that of the source instrument; modifications were made wherever necessary. This version was then reviewed by two monolingual individuals who were unfamiliar with the instrument. The suggestions made by them were reviewed by the bilingual panel and were incorporated into the translated instrument wherever found appropriate. This translated instrument was then translated back into the language of the source instrument by another individual who was informed that the instrument was concerned with health, to ensure the use of the proper methodology without introducing bias into the process. The translated instrument and the source instrument were administered to a group consisting of patients and healthy individuals. They were asked to comment on the correspondence between the languages in both the instruments at question-to-question level. Modifications suggested were reviewed by the bilingual group and incorporated wherever necessary. The instrument was further refined based on the moderated interviews as described previously.
| Stage 4: Validity and reliability|| |
Validity is concerned with whether the instrument actually measures the underlying concept or not and it involves assessing the instrument against a standard criterion. We did not assess validity of the modified WHOQOL as it was only an adaptation of a WHOQOL instrument that is already validated.
We assessed the internal consistency and reproducibility of the modified instrument in order to assess its reliability as in a different language. Reliability assesses whether the instrument consistently produces similar results or not. Internal consistency was assessed using the Cronbach's α
 which is a coefficient used to assess whether the items used to measure a particular aspect on a scale correlate with one another or not. Reproducibility of the instrument was assessed by evaluating the results obtained on repeated administration of the instrument by following two approaches. The subjects were divided into two groups. The first group with 117 subjects (52 females), age ranging from 16 to 75 years (38.8±14.7 [mean ± standard deviation] years) had repeated administration of the instrument by different interviewers (inter-interviewer reproducibility) with a gap of at least three days after the first administration. The second group with 55 subjects (27 females), age ranging from 16 to 75 years (42.6±14.2 years) had repeated administration of the instrument by the same interviewer (intra-interviewer reproducibility) with a gap of at least three days after the first administration. We had three interviewers who had undergone extensive training for administering the instrument before testing the reproducibility of the instrument. The percentage agreement between a pair was calculated for each question (facet) of the instrument. To calculate this percentage agreement, the responses in the response scales were classified into groups based on the magnitude of the effect on QOL. The responses for the intensity, frequency, and evaluation response scales were classified into three groups: response (0 & 1), (2), (3 & 4), and those of the capacity response scale were classified into two groups: (0, 1 & 2), (3 & 4). Reproducibility along with the 95% confidence intervals is reported.
The generic WHOQOL was modified into a health-related QOL by adding a follow-up question to each selected facet. The follow-up question is shown in [Table - 1].
| Content|| |
All the domains of the WHOQOL were included. The domains and facets selected for the proposed instrument are listed in [Table - 2]. One facet in the social relationships domain (sexual activity) and three facets in the environment domain (home environment, health and social care, physical environment) were excluded in the provisional list for the proposed instrument. The questions on mobility and activities of daily living were made more specific to the type/activity based on the moderated interviews; the idea for this was partly taken from elsewhere. A question specific to driving was also added in 'level of independence' domain to be asked of those who were driving presently and also to those who used to drive in the past.
| Response scale|| |
The response scale that was most suited to elicit health-related QOL was the intensity scale with a few exceptions: overall QOL, health and vision, personal relationships, and financial resources were best assessed by the evaluation scale; frustration and depression by the frequency scale; and social support by the capacity scale. Examples of the response scales are listed in [Table - 3].
| Scoring system|| |
For the first step in scoring, we followed the similar concept of scoring as of the WHOQOL. The domain scores were calculated by summing the facets within the domain, and dividing the summated facet scores by the number of facets in that domain. If a facet has two or more questions, the summated score of all the questions in that facet was divided by the number of questions in that facet to obtain the score for the particular facet.
For the second step in scoring, the following scoring system was developed in order to account for the modifications made by us in the WHOQOL. All the facets are scored from a minimum score of 0 to a maximum of 4, irrespective of the type of response scale used so that all the facets have a similar scoring system. When a subject reported a decrease in QOL in a particular facet due to two or more health problems, the most important health problem was given double the weightage compared to the others in calculating their contribution to decrease in QOL.
We modified the WHOQOL scoring system into a unidirectional scoring system wherein a lower score signified better QOL irrespective of the domain/facet, as it was realised during the focus groups and the moderated interviews that the chances of error in calculating the score were higher because of two different types of scoring systems in the WHOQOL. The scoring system is shown with the response scales in [Table - 3].
| Translation|| |
The modified instrument was translated into Telugu, by the pragmatic approach wherein the source instrument is adapted for use in the target culture only so far as it can be regarded to have validity in that culture.
| Reliability|| |
Values of the Cronbach's α for each domain are listed in [Table - 4]. Three facets (activities of daily living, mobility, and negative feelings) are assessed with more than one question and the Cronbach's α for these are listed in [Table - 5].
The mean and standard deviation of the responses to the facets in the physical domain ranged from 0.19±0.53 (mean±SD) to 0.59±0.90; psychological domain from 0.01±0.40 to 1.92±0.86; level of independence domain from 0.01±0.08 to 0.84±0.37; social relationships domain from 1.86±0.62 to 2.70±0.81; environment domain from 2.10±0.86 to 3.21±0.91; and religion domain, 0.01±0.27.
For inter-interviewer reproducibility, the mean percentage agreement (95% CI) for the three pairs of interviewers was 91.7% (88.9-94.5%), 94.3% (92.0-96.8%), and 91.9% (88.8-95.0%) for the total health-related QOL instrument. The agreement for the facets ranged from 72.2% to 100%. For intra-interviewer reproducibility, the mean percentage agreement (95% CI) for each of the three interviewers was 97.4% (96.2-98.6%), 94.4% (91.8-97.0%), and 98.5% (96.8-100%) for the total QOL instrument. The agreement for the facets ranged from 69.3% to 100%.
The average time for administration of the instrument ranged between 10-20 minutes.
| Discussion|| |
In simple terms, QOL reflects people's way of life, their occupation, their income, level of relaxation and stress, their relations with others in the society and the conditions in which they live and work. Not many instruments are available in the developing world to measure health-related QOL. Hence, we modified the generic WHOQOL to an health-related QOL instrument in order to use this in a population-based study to develop a vision-specific QOL instrument.
We added a follow-up question to assess whether the decrease in QOL was due to eye-related problems or other health-related problems. Patients with eye problems are being studied in APEDS to assess how these problems affect their quality of life. This population-based assessment would help us determine those aspects of QOL that are likely to be affected by visual impairment.
We included all the domains of WHOQOL in the proposed instrument but excluded a few facets. The facet on sexual activity was excluded because of the conservative culture of our country, and three facets from the environment domain were excluded as it was felt that people may not be able to relate to these clearly in our setting. We found the intensity scale to be most suited to evaluate health and vision-related QOL in our focus groups. A unidirectional scoring system was developed to avoid possible errors due to two different scoring systems. We found this system to be acceptable. The system of double weightage for the most important health problem for subjects reporting a decrease in QOL in a particular facet due to two or more health problems was decided with the arbitrary assumption that the most important health problem would cause at least twice the amount of decrease in health-related QOL compared to the other causes of decreased QOL. This would enable us to compare the decrease in QOL due to different health problems and hence in identifying the aspects of QOL that are affected by visual impairment.
This QOL instrument was developed for use in APEDS and hence was translated into the local language, Telugu. It is likely that all the domains and facets of QOL that are measured are relevant to the other states of India but modifications in some questions may be necessary when translating the instrument into other languages for use in other states of India.
We did not assess the validity of the modified instrument as the WHOQOL is cross-cultural and has been validated. The domains and facets of this instrument were selected based on the focus group discussions and the moderated interviews; they represent their relevance to QOL and were well understood and accepted by subjects who participated in the focus groups and moderated interviews.
Global measures created from generic health status measures often have high test-retest and internal consistency reliability, although individual items may have markedly reduced reliability coefficients. Values of Cronbach's α between 0.7 and 0.8 are regarded as satisfactory for comparing groups, though higher values are needed for clinical application. The internal consistency of the modified instrument was within acceptable standards of reliability except for the social relationships and environment domains. This is probably because both these domains are assessed by facets which assess different aspects of these domains. The facets in the psychological, social relationships, and environment domains elicited a broad range of responses but the physical, level of independence, and religion domains had a ceiling effect because the majority of the responses were on the "good" side of the scale. We think that this is reflective of the distribution in our population for these domains.
All the three interviewers showed high levels of inter-interviewer reproducibility suggesting that it is not necessary to have the same interviewer in a longitudinal study as it is possible to train interviewers to maintain the conceptual basis of the questions. All the three interviewers also showed high levels of intra-interviewer reproducibility, suggesting that patients gave consistent responses to the same questions.
We believe that the time for administration of the proposed instrument was within the average attention span of a person; this was dependent on the level of QOL for each subject.
The clinical literature on treatment of eye disease has continued to focus almost exclusively on measures of visual impairment, with only limited consideration to broader measures of health status. Frequently, the assessment of treatment effects is limited to visual acuity and visual field. QOL assessment can not replace the existing measures of assessing morbidity but can give an additional insight into the impact of impairment or disability on a patient's life. The proposed health-related QOL instrument can be used to measure the impact of various health problems on QOL including that of vision; it allows comparison between the impact of different health problems on QOL as the basic generic nature of the questions is maintained. Results with this instrument from the population-based APEDS could lead to development of a cross-cultural vision-specific QOL instrument. Other disease-specific QOL instruments could also be developed. Having an international vision-specific QOL instrument could potentially make it possible to carry out vision-specific QOL research collaboratively in different cultural settings, and to directly compare results obtained in different settings.
| Acknowledgments|| |
This study was supported by the Hyderabad Eye Research Foundation, Hyderabad, India. Rakhi Dandona is supported in part by the R.B. McComas scholarship from the University of Melbourne, Melbourne, Australia.
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[Table - 1], [Table - 2], [Table - 3], [Table - 4], [Table - 5]
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