The Spanish Version of the Quality-of-Life in Epilepsy Inventory (QOLIE-3 1): Translation, Validity, and Reliability

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1 Epikpsia, 40(9): , 1999 Lippincott Williams & Wilkins, Inc., Philadelphia 0 Internalional Leaguc Against Epilepsy Clinical Research The Spanish Version of the QualityofLife in Epilepsy Inventory (): Translation, Validity, and Reliability Xavier Torres, *Santiago Arroyo, Susana Araya, and Joan de Pablo Servicios de Psiquiatria y *Neurologia, Hospital Clinic de Barcelona, Barcelona, Spain Summary: Purpose: Spanish adaptation of the Quality of Life in Epilepsy Inventory (QOLIE31). Methods: Internal consistency and construct validity of the Spanish translation of the QOLIE31 were tested in 252 patients with epilepsy. Patients also were administered the General Health Questionnaire (GHQ28), and the Nottingham Health Profile (NHP). Two weeks after the first test, a subgroup of randomly selected patients were readministered the QOLIE 31 along with a new fiveoptiori question about change in health status. Patients reporting no change in health status were included in the study of temporal stability. Sensitivity to clinical change was assessed in 31 additional patients who had successfully undergone epilepsy surgery. Results: The QOLIE31 was highly correlated with the GHQ28 (r = 0.63) and the NHP (r = 0.69), demonstrating construct validity. Cronbach s alpha coefficient was 0.92, showing the items of the QOLIE31 to be interdependent and homogeneous. For a 2week test retest, both Pearson productmoment correlation and intraclass correlation coefficients were 0.90, indicating temporal stability. Sensitivity to clinical change was suggested by a significant mean difference between the global scores both before and after epilepsy surgery (21 27, p i ; 95% CI, to 15.66). The standardized response mean of the global score was 1.67, and the effect size was 1.35, both indicating large clinical change as a result of seizure relief. Conclusions: The similarity of psychometric properties between the English and the Spanish versions of the QOLIE3 I supports their conceptual equivalence. The questionnaire s responsiveness to clinical change suggests its utility in outcome assessment of drug trials and epilepsy surgery. Key Words: Quality of lifeepilepsyepilepsy surgeryvalidation of psychological test. In recent years there has been an increased demand for measures that analyze and reflect the viewpoints of users of health services. The focus of these demands is aimed at assessing quality of life as a measure of outcome in clinical practice and/or drug trials, along with evaluating the allocation of health care resources. The phenomenon of qualityoflife studies can be traced to the research of Karnofsky et al. (1) dating back some 50 years (1) and since has been apparent in epilepsy. The workshop sponsored by the international League Against Epilepsy in Porto, Portugal, in 1992 concluded that the epilepsy population called for a specific measure of quality of life. Later, at the American Epilepsy Society meeting in December 1992, the QualityofLife in Epilepsy (QOLIE) Development Group reported on its work in developing such a measure (29), which culminated in 1993, Accepted February 1 I, Address correspondence and reprint requests to Dr. X. Torres at Servicio de Psiquiatria, Hospital Clinic de Barcelona, Villarroel 170, Barcelona 08036, Spain. thus providing a valid inventory for use in both clinical practice and research. Several generic measures of quality of life are available in Spanish. However, except for the Washington Psychosocial Seizure Inventory (WPSI) (lo), no single measure targets those topics specific to epilepsy. A crosscultural translation of the is currently amiable (1 1) but has not been validated. Recently a qualityoflife scale for use in Spain was proposed (the Ficha Evolutiva Global de Epilepsia en el Adulto, FEGEA) (1 21 3); however, it is not validated, and, as the authors claim, it is more a clinical interview than a pure qualityoflife scale. In view of this, we decided to adapt a specific measure of quality of life in epilepsy (QOLIE31) with the same level of validity and reliability as the original version, while ensuring the cultural accuracy of the newly adapted version. Otherwise, as we were particularly concerned with the QOLIE31 ability to detect clinical changes, the assessment of drugresistant patients with epilepsy who had become seizure free after epilepsy surgery was included. 1299

2 1300 X. TORRES ET AL. METHODS The QualityofLife in Epilepsy Inventory (QOLIE31) The QOLIE31 was developed in effort to assess healthrelated quality of life in patients with epilepsy (29). The questionnaire contains 3 1 items, 16 of which were drawn from existing sources, which include other questionnaires (1419), and 15 were developed by the QOLIE Development Group. The contains seven multiitem scales that tap the following health concepts: Seizure Worry (SW), Overall QualityofLife (OQL), Emotional Wellbeing (EWB), Energy Fatige (E/F), Cognitive functioning (COG), Medication Effects (ME), and Social Functioning (SF). The scoring procedure for the QOLIE31 converts the raw precoded numeric values of items to 0100 scores, higher scores always reflecting better quality of life. An overall score may be obtained by using a weighted average of the multiitem scale scoses (20). According to the original version, the recall period used in our study was the last 4 weeks for all patients, except the retest ones, whose recall period was shortened to the final 2week testretest period. Generic healthrelated qualityoflife measures In addition to QOLIE31, the General Health Questionnaire (GHQ28) and the Nottingham Health Profile (NHP) also were administered. The GHQ28 is designed to detect patients with potential psychiatric disorders in the general population. It contains 28 items and has been adapted for use in Spain in accordance with the Spanish culture (21). The NHP is a perceived health questionnaire that generically measures the patient s quality of life. The Spanish version of the NHP has been shown to be equivalent to the original in regard to psychometric properties and adjusted to cultural variations (22,23). It contains 38 items grouped in six scales that tap six health dimensions: Energy (EN), Pain (P), Emotional Reactions (EMR), Sleep (SL), Social Isolation (SOIS), and Physical Mobility (PHM). The NHP scores range from 0 to 100, and an overall score is obtained by using the average of the scores from each scale. Adaptation of the QOLIE31 into Spanish The adaptation process of the into Spanish included the following phases: translation into Spanish, assessment of item comprehension, backtranslation into English, development of a consensual version, and formal assessment of its validity and reliability (24). Although a crosscultural translation of the into Spanish is currently available (1 l), it was not when our study began, so we conducted an independent translation. The previously mentioned MAP1 version has been reviewed by our experts and, although slight differences have been detected, we think that both could be used alternatively. Translation into Spanish was conducted by a bilingual translator independent of the study. This first Spanish version was then backtranslated and discussed by a panel of experts until agreement was reached on item wording according to content correspondence. The final version was tested in a pilot study including 20 patients with epilepsy, which confirmed a high level of item acceptance and comprehension. Assessment of validity and reliability To assess the validity and reliability of the QOLIE31, a sample of consecutive nonhospitalized patients with epilepsy from the Neurology Service of the Hospital Clinic de Barcelona was chosen. Patients were considered eligible if they had been diagnosed by an epileptologist and if their age was between 18 and 65 years. The final sample consisted of 252 patients. To assess the questionnaire s responsiveness to clinical change, a sample of 31 consecutive patients with drugresistant epilepsy who also were candidates for epilepsy surgery from the Epilepsy Unit of the Hospital Clinic de Barcelona also was chosen. All questionnaires were selfadministered. The outpatients completed the questionnaires during their visit to the Neurology service. Two weeks after the first survey, the QOLIE31 was readministered to a random subgroup of outpatients, along with a 5point response question reflecting their opinions regarding their health status (as opposed to the 2 prior weeks). Patients who reported no changes in their health status during this period were selected for the testretest reliability analysis. To assess the sensitivity to clinical change, 31 patients with drugresistant epilepsy were selected, all of whom were seizure free 6 months after epilepsy surgery. Questionnaires were completed during the week of videoeeg monitoring, in the Epilepsy Unit. The researcher administering the questionnaires was responsible for ensuring that patients of both groups were able to understand and complete all questionnaires correctly. Analysis The KolmogorovSmirnov test for normality was applied to the global scores from the three questionnaires and their dimensions. Pearson s productmoment coefficient was calculated between the global score and its subscales, the GHQ28 global score and the NHP global score and its dimensions. As a measure of convergent validity, we expected to find strong correlations between scales similar in content (i.e., Emotional WellBeing and NHP Emotional Reactions). To assess discriminant validity, we expected to find stronger correlations between NHP and scales similar in content than between scales a priori not related (i.e., QOLIE31 Medication Effects and NHP Pain). Internal consistency of the QOLIE31 and its subscales was analyzed by using Cronbach s ci coefficient.

3 SPANISH VERSION OF THE QUALITY OF LIFE IN EPILEPSY INVENTORY 1301 Testretest reliability was assessed by using the Pearson s productmoment coefficient, intraclass correlation coefficients, and Student s t test for repeated measurements only in the group of outpatients who reported no change in their health status. The sensitivity to clinical change was analyzed by using Student s t test for repeated measurements, effect sizes (ES) (25,26), and the standardized response mean (SRM) (27) in the group of drugresistant patients with epilepsy who underwent epilepsy surgery and were seizure free. The Effect Size is calculated as mean change in score in the surgery group divided by the standard deviation of the initial mean score in that group. An ES of is defined as small, one of 0.50 as moderate, and one of as large (28). The SRM is equal to the mean change in score divided by the standard deviation of individuals changes in scores. An SRM of 0.2 indicates a small clinical change, 0.5 to 0.8 moderate, and 0.8 a large clinical change. RESULTS The sample of 252 outpatients was composed of 132 women (52.4%) and 120 men (47.6%), with a mean age of years (SD, years). The overall and dimensional scores for the QOLIE31 and the other measures in the outpatient group are presented in Table 1. The internal consistency for the overall score and dimensions was high (Table 1). The Cronbach s (Y coefficeint was 0.92 for the overall score and between 0.55 and 0.83 for the rest of the dimensions. Correlation coefficients between the scores of the three questionnaires are presented in Table 2. The TABLE 1. Mean scores of the QOLIE31, GHQ28, and NHP for the outpatient population and internal consistency of QOLIE31 Mean score (SD) Cronbach s (17.33) 0.92 Seizure Worry 5 I.47 (29.73) 0.83 Overall Quality of Life (16.95) 0.55 Emotional WellBeing (19.13) 0.77 Energy/Fatigue (20.27) 0.77 Cognitive Functioning (23.80) 0.82 Medication Effects (29.10) 0.77 Social Functioning (27.96) 0.77 GHQ (5.81) NHP (16.23) Energy (30.07) Pain (18.92) Emotional Reactions (24.91) Sleep (26.54) Social Isolation (24.49) Physical Mobility i0.68 (17.74) Higher scores in the QOLIE31 reflect better quality of life, whereas higher scores in the GHQ28 and the NHP indicate worse status. overall score correlated negatively with the GHQ28 (Y = 0.63) (p < 0.001) and NHP (Y = 0.69; p < 0.001) overall scores, indicating strong agreement between the questionnaires. By subscales, correlation coefficients between the QOLIE31 and the GHQ28 ranged from 0.27 to 0.61, and between the QOLIE31 and the NHP, from 0.06 to As a measure of convergent validity, relatively strong correlations between QOLIE31 and NHP scales of similar content were found: Emotional WellBeing and NHP Emotional Reactions (Y = 0.67; p < O.Ol), EnergyEatigue and NHP Energy (Y = 0.43; p < O.Ol), and QOLIE31 Social Functioning and NHP Social Isolation (Y = 0.40; p < 0.01). These correlations were higher than corresponding correlations between these scales and the other NHP scales. Otherwise low and essentially nonsignificant correlations were found between scales of dissimilar content: Medication Effects and NHP Pain (Y = 0.16; p > 0.05) and Sleep (r = 0.06; p > 0.05) or QOLIE31 scales and NHP Physical Mobility, indicating discriminant validity. The temporal stability of the questionnaire was studied with Pearson s productmoment correlation and Intraclass correlation coefficients, along with the mean differences between testretest response from the patients who reported no change in their health status (Table 3). Correlation coefficients ranged from 0.62 to 0.90 (p < 0.001). Intraclass correlation coefficients ranged from 0.63 to No differences were found between the mean scores of both administrations. Responsiveness to clinical change Table 4 shows the demographic and neurologic characteristics of the 3 1 patients with drugresistant temporal lobe epilepsy who underwent epilepsy surgery. Table 5 shows the mean differences between the scores of those patients who underwent epilepsy surgery, paired t statistics, standardized response means and effect sizes. Statistically significant differences were found in all dimensions, ranging from 9.41 (p < 0.05; 95% CI, to 0.72) to (p < ; 95% CI, to 33.92). The detected significant clinical improvement, with SRMs ranging from 0.43 (moderate clinical change) to 1.67 (large clinical change) and effect sizes ranging from 0.43 (moderate effect size) to 1.58 (large effect size). DISCUSSION The Spanish version of the has shown psychometric properties comparable to those of the American version, and thus may be used as a specific measure of quality of life in Spanish patients with epilepsy. We have shown the Spanish version of the to be highly correlated with the GHQ28 (r = 0.63) and Epilqsiu, Vol. 40. No. 9, 1999

4 ~ ~ 1302 X. TORRES ET AL. TABLE 2. Matrix of correlations between QOLIE3 I, GHQ28, and NHP in the outpatient population Seizure Worry Overall Quality of Life Emotional WellBeing EnergylFatigue Cognitive Functioning Medication Effects Social Functioning GHQ28 NHP Energy Pain Emotional Reactions Sleep Social Isolation PHM SW OQL EWB EIF COG ME SF I h h 0.36h b I I n = 252. Pearson s productmoment coefficient I p < p < the NHP (r = 0.69), which confirms its convergent validity. Convergent validity also is supported by relatively strong correlations, all of which were significant (p < O.Ol), between QOLIE31 and NHP scales of similar content (i.e., Emotional WellBeing and NHP Emotional Reactions; Energy/Fatigue and NHP Energy; and QOLIE31 Social Functioning and NHP Social Isolation). These correlations were higher than corresponding correlations between the mentioned scales and the rest of NHP scales, except for QOLIE31 Energy/Fatigue and Social Functioning and NHP Emotional Reactions. One possible explanation for this finding is the wellknown impact of emotional wellbeing on energy level and social functioning, as shown by the strong correlations between the scales that tap these areas. Discriminant validity also was supported by findings that low and essentially nonsignificant correlations were found between the and NHP scales that measure dissimilar constructs (i.e., Medication Effects and NHP Pain and Sleep, or QOLIE31 scales and NHP Physical Mobility). We also found some differences from the validation of the original English version on the medication effects scale. In this subscale, correlation coefficients were moderate with overall score and dimensions, the GHQ28, and the NHP overall score, and not significant with some of the NHP scales. One possible explanation for these results is that, in our sample, many patients reported an unusual absence of antiepileptic medication (AED) effects, that is, a better status than expected in this aspect of their disease in comparison to the rest of the dimensions. The items are interdependent and homogeneous in terms of the concepts they measure, as indicated by the high Cronbach s a coefficients. However, the Cronbach s a for the Overall Quality of Life scale was below the generally accepted standard of 0.70, and below TABLE 3. Mean and mean differences of the QOLIE31 test and 2week retest scores. Pearson s productmoment, and intraclass correlation coefficients Seizure Worry Overall QOL Emotional WellBeing EnergyiFatigue Cognitive Functioning Medication Effects Social Functioning p < Test [mean (SD)] (16.78) (28.95) (16.23) (16.00) (18.41) 66. I 1 (22.93) (28.53) (26.68) Retest [mean (SD)] Difference r ICC (17.13) (27.58) (14.15) (19.30) (20.75) (25.16) (26.98) (18.92) Epilepsia, Vol. 40. No. Y, 1999

5 SPANISH VERSION OF THE QUALITY OF LIFE IN EPILEPSY INVENTORY 1303 TABLE 4. Baseline charucteristics of drugresistant epilepsy surgery putients Gender Male Female Age (yr)" Age at onset of epilepsy" Duration of epilepsy" Etiology Unknown Trauma Meningitis Tumor Other Hippocampal sclerosis Yes No Type of seizure Simple partial Complex partial Complex partial secondarily generalized Seizure frequency 13lmo 4 I 2/mo > I21mo Hemisphere Left Right n = 31. Means (SD); all other values are numbers of patients. 17 (54.8%) 14 (45.2%) (8.59) (8.56) 19.2 (9.13) 16 (5 1.6%) 6 (19.3%) I9 (61.3%) 12 (38.7%) 22 (70.9%) 6 (19.4%) 8 (25.8%) 19 (61.3%) 4 (12.9%) 18 (58%) I3 (42%) the ci coefficient in the original version. The Overall Quality of Life is a twoitem scale, and a. is dependent on both number of items and interitem correlations, which might account for the relatively smaller ci compared with the other QOLIE31 scales. As this finding might compromise the scales' reliability, efforts to improve its reliability, for instance by adding some items, should be a priority of future research. The high correlation and intraclass correlation coeffi cients along with the absence of mean differences between the scores obtained in those patients reporting no changes in their health status (between the test and the retest administrations) support the temporal stability of the questionnaire. However, the productmoment correlation and intraclass correlation coefficients for the Medication Effects scale were slightly below the standard of One possible explanation to this finding is that due to the unusual abscence of AED side effects found in our outpatient population, these coefficients might be reflecting slight changes from a better status than expected in comparion to the rest of dimensions. We also confirmed that the QOLIE31 is sensitive to clinical change in view of the significant differences between the scores obtained in the group of patients who underwent epilepsy surgery and were rendered seizure free, and their high Standardized Response Means and Effect Sizes, indicating large clinical change. However, only moderately significant differences were observed in the cognitivefunctioning subscale, possibly because cognitive functioning does not usually improve after surgery. Our results about responsiveness agree with previous studies (29,31). In contrast to our findings, McLachlan et al. (32) showed that significant differences in a related measure, the Epilepsy Surgery Inventory 55 (ESI55), after temporal lobectomy take almost 2 years to evolve and to become fully evident in patient reports, which might make our results excessively optimistic. However, in contrast to the sample of McLachlan et al., our patients rendered seizure free at 6 months followup agree with previous studies (33) showing that functional improvement at 6 months' followup is limited to completely seizurefree patients. Otherwise the most significant improvements detected in our study were in Seizure TABLE 5. Mean, meun differences, stundurdized iesponse means, and effect size in the QOLIE31 before und 6months after surgerl)? Pre Post Difference (SD) [mean (SD)] [mean (SD)] (95% CI) t SRM ES (16.06) (9.92) (15.69) (28.08; 15.66) 1.24" Seizure Worry (28.30) (14.18) (26.69) (55.04; 33.92) 8.66" Overall QOL (16.54) (1 2.04) (16.06) 5.69" (23.95;11.24) Emotional WellBeing EnergyFatigue Cognitive Functioning Medication Effects Social Functioning n = 31. 'I p < " p < (17.37) (17.54) (22.00) (21.60) (28.00) (13.75) (14.37) (19.31) (24.94) (16.63) (20.42) (35.60; 19.44) (19.28) (34.85; 19.60) 9.41 (21.95) (1 8.09; 0.72) (30.52) (37.70; 13.55) (29.40) (36.10; 12.84) 7.00" 7.34" 2.23' 4.36" 4.33" Epilepsia, Vol. 40, No. 9, 1999

6 1304 X. TORRES ET AL. Worry, Emotional WellBeing and Energy/Fatigue scales, which contrasts with the McLachlan et al. findings, in which emotional wellbeing and physical function domains of ESI55 remained stable at 24 months followup regardless of the degree of seizure reduction. However, as McLachlan et al. stated, the postoperative groups in their study were composed of different subsets of their sample, which might compromise the comparability of both studies. Of special interest is the Vickrey et al. (34) finding that auras may constitute a special group, different from other postoperative seizures in terms of the impact and impairment produced, with ESI55 health perceptions the most sensitive scale to seizure classification. Further research is needed to determine which scales of the QOLIE31 are most sensitive to every type of seizure. 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