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A general population study of the Chinese Whiteley-7 Index in Hong Kong
Journal of Psychosomatic Research 71 (2011) 387–391
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Journal of Psychosomatic Research
A general population study of the Chinese Whiteley-7 Index in Hong Kong Sing Lee a, b, c,⁎, King Lam Ng a, Yee Ling Ma a, Adley Tsang c, Kathleen P.S. Kwok c a b c
Department of Psychiatry, The Chinese University of Hong Kong, Hong Kong, China Department of Global Health and Social Medicine, Harvard Medical School, Boston, MA, USA Hong Kong Mood Disorders Center, The Chinese University of Hong Kong, Hong Kong, China
a r t i c l e
i n f o
Article history: Received 18 March 2011 Received in revised form 31 May 2011 Accepted 31 May 2011 Keywords: Chinese population Health anxiety Reliability Validity Whiteley Index
a b s t r a c t Objective: To examine the psychometric properties of the Chinese seven-item Whiteley Index (WI-7) in the general population of Hong Kong. Methods: A random community-based telephone survey of 3014 respondents aged 15–65 was conducted using a fully structured questionnaire that included the WI-7, 15-item Patient Health Questionnaire (PHQ15), Sheehan Disability Scale (SDS), and items about the frequency of health service use, perceived helpfulness of doctors, level of satisfaction with doctors, and sociodemographic variables. A sub-sample of 199 respondents was re-interviewed to assess test–retest reliability. Results: The WI-7 exhibited satisfactory internal consistency (Cronbach's α=0.73) and stable one-month test-retest reliability. The most commonly endorsed item was “worrying a lot about one's health” (55.7%), followed by “worrying about getting the disease oneself if it is brought to his/her attention” (48.7%) and “bothered by many different pains and aches” (33.9%). Age, gender, and monthly family income significantly predicted WI-7 score. Confirmatory factor analysis revealed that a 2-factor structure was superior to a 1-factor structure in fitting the data. WI-7 total score was positively associated with PHQ-15 somatic distress, SDS impairment, number of healthcare visits, lower levels of perceived helpfulness of doctors and of satisfaction with doctors. Conclusion: The Chinese WI-7 exhibits satisfactory reliability and internal validity in a general population. It is a promising tool for the empirical examination of health anxiety which is a common experience with a mostly typical epidemiological profile among Chinese people in Hong Kong. © 2011 Elsevier Inc. All rights reserved.
Introduction Health anxiety lies on a spectrum of intensity [1,2] and is common in both clinical [3] and community [4] settings. Even when not reaching the clinical diagnostic threshold of hypochondriasis, it can be impairing, cause difficult doctor–patient relationship, and increase healthcare cost [5–7]. Health anxiety is responsive to cognitivebehavioral therapy [8], but is often not assessed clinically. Moreover, mainstream epidemiological research usually does not examine health anxiety except for the diagnosis of hypochondriasis which is uncommon at a general population level [9]. These are despite the fact that a number of instruments are available for the dimensional assessment of health anxiety. Some of these instruments, such as the 29-item Illness Attitude Scales [10] and the 31-item Cognitions About Body And Health Questionnaire [11], may be too lengthy to administer in time-limited clinical and epidemiological settings. They also do not address certain ⁎ Corresponding author at: Hong Kong Mood Disorders Center, 7A, Block E, Staff Quarters, Prince of Wales Hospital, Shatin, N.T., Hong Kong, China. Tel.: +852 2144 5338; fax: +852 2144 5129. E-mail address: [email protected] (S. Lee). 0022-3999/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.jpsychores.2011.05.013
core features of health anxiety such as somatic symptoms and disease conviction [7]. The 14-item Whiteley Index (WI-14) is the first selfreport measure designed to assess health anxiety. It comprises of 14 items that assess the affective, cognitive and somatic components of hypochondriasis, namely bodily preoccupation, disease phobia, and disease conviction [2]. It has been widely used and shown to exhibit good internal consistency, test–retest reliability, convergent validity, and concurrent validity [7,12]. A shorter version, namely the 7-item Whiteley Index (WI-7), is also available and contains 7 of the original 14 items of the WI-14 [13]. It demonstrated excellent psychometric properties in primary care samples, with good sensitivity and specificity for screening DSM-IV somatization disorder and hypochondriasis respectively [3,13]. Two correlated and overlapping constructs, namely, illness worrying and illness conviction, are generally found to be embedded in the WI-7 in Western populations [13], but confirmatory factor analysis has yet to be conducted to examine whether this factor structure is applicable to other populations. Health anxiety is closely associated with somatization and increased healthcare visits in Western populations [5,7,14,15]. Although somatization [16] and doctor-shopping [17] are common in Hong Kong, there has been no community or clinical epidemiological study of health anxiety in Chinese and most other Asian populations. This may be due to
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the lack of a brief and suitable tool for assessing health anxiety in Chinese people. In fact, nearly all previous studies of the psychometric properties of the Whiteley Index were conducted in Western clinical samples [15,18–20]. The aim of the present study was to examine the psychometric properties of the Chinese WI-7 in the general population of Hong Kong. Method Sampling This two-stage study was approved by the research ethics committee of The Chinese University of Hong Kong. In the first stage, a random telephone survey of the general population aged between 15 and 65 years was conducted between September 2 and 22, 2009. As over 99% of the domestic households in Hong Kong have a telephone at home and very few of them have more than one telephone line [21], sampling telephone lines based on the updated residential telephone directory should generate a representative sample of households. In our study, 29,000 telephone numbers were randomly selected from the latest Residential Telephone Directory by computer and the last two digits were replaced by computer-generated random numbers to capture unlisted telephone numbers. A non-contact status was assigned to telephone numbers that could not be contacted after three attempts on different days, invalid telephone numbers generated by computers, fax numbers, non-residential numbers, and line busy (n=17,880). In each successfully contacted residential unit, only one person was interviewed. Overall, 11,120 calls were made that had successfully established contact with the household, of which the breakdown is as follows: no interviewee aged between 15 and 65 years in 1625 calls, people hung up immediately in 4004 calls, and rejected the interview in 2477 calls. Thus, 3014 interviews were successfully completed. Of the households that were successfully contacted and had interviewees within the age range, the participation rate was 54.9% (3014/[3014+2477]×100%). Informed verbal consent was obtained prior to each successfully completed interview, which took an average of 7.4 min (SD=1.9 min). The sample was weighted according to the gender distribution of different age groups in Hong Kong as reported by the Census and Statistics Department of the Hong Kong Government. With a 95% confidence level, the maximum sampling error was ±1.76%. In order to establish the test–retest reliability of the WI-7, a sub-sample of 199 respondents (6.6%) was conveniently drawn from those (n=1128) who had completed the first stage of the telephone survey and agreed to be contacted again for the second administration of the survey. They were re-interviewed by phone between 19 and 49 days (average=27.9 days) in the second stage of the study. Instruments An independent survey research organization, the Hong Kong Institute of Asia-Pacific Studies of The Chinese University of Hong Kong, was commissioned to conduct the survey. The interviewers were university students with 1–3 years of part-time experience in administering telephone survey interviews, including those on mental disorders. They were given a briefing session to familiarize themselves with the fully structured questionnaire used. The interview was conducted in Cantonese Chinese, the predominant dialect used in Hong Kong. The questionnaire included Chinese versions of the 15-item Patient Health Questionnaire (PHQ-15), WI-7, Sheehan Disability Scale (SDS), items probing the frequency of health service use, perceived helpfulness of doctors, level of satisfaction with doctors, and sociodemographic variables. The WI-7 allows a dichotomous choice of “yes” or “no” (Table 1). The 7 items were carefully translated by the lead author, an experienced bilingual clinician and researcher, and were found to be readily understood by Chinese speaking psychiatric patients and non-patients.
Table 1 The frequency distribution and factor loadings of the 7-item Whiteley Index Frequency of symptoms Total sample (n=3014) Whiteley 7 items (English)
n
%
Factor Factor loadings of loadings of a 1-factor model 2-factor modelb,c
1. Do you think there is something 662 22.0 0.72 seriously wrong with your body? 2. Do you worry a lot about your 1679 55.7 0.75 health? 487 16.2 0.59 3. Is it hard for you to believe the doctor when he or she tells you there is nothing to worry about? 762 25.3 0.80 4. Do you often worry about the possibility that you have a serious illness? 5. Are you bothered by many 1022 33.9 0.71 different pains and aches? 6. If a disease is brought to your 1468 48.7 0.60 attention (e.g. on TV, radio, the newspapers, or by someone you know), do you worry about getting it yourself? 7. Do you find that you are bothered 904 30.0 0.74 by many different symptoms?
0.80 0.61
0.87
0.79 0.67
0.81
a
Factor loadings of the 1-factor model in our sample. Factor loadings of the 2-factor model in our sample. Items #2, #4, and #6 were loaded on “illness worrying” factor; items #3, #5, and #7 were loaded on “illness conviction” factor. b c
A score of “1” was given for each “yes” response and the total score (range 0–7) was obtained additively [22,23]. Permission to use the Cantonese Chinese version of the PHQ-15 was obtained from Pfizer New York. The PHQ-15 asks respondents to rate how much they have been bothered by each of 15 symptoms during the past 4 weeks on a “0” (not bothered at all) to “2” (bothered a lot) scale, with the total score ranges from 0 to 30 [24]. The Chinese PHQ-15 exhibited satisfactory reliability and validity in the same sample of respondents who participated in the present study [16]. The SDS was used to assess role impairment on four domains of life in the past four weeks, which include household responsibilities (“doing housework, such as cleaning and grocery shopping”), work/school (“the ability to work, such as working, studying, or taking exams”), close relationships (“the ability to form and maintain close relationships with other people, such as romantic partner, family members, or close friends”), and social life (“the ability to form social relationship”), all of which were rated on a scale of 0 to 10 (none (0), mild (1–3), moderate (4–6), severe (7–9) and very severe (10)) [25]. The SDS is widely used in both Western and Chinese community psychiatric surveys [16]. Frequency of health service use was assessed by asking “in the previous year, how often on average did you seek help from health professionals?” There are seven response categories ranging from “nil in the previous year” to “once a week or more”. Perceived helpfulness of doctors was assessed on a scale from 0 to 5, with “0” representing “completely not helpful” and “5” representing “very helpful”. Level of satisfaction with doctors was assessed similarly on a scale from 0 to 5, with “0” representing “strongly dissatisfied” to “5” representing “strongly satisfied”. Statistical analysis Cross-tabulations were conducted to estimate the percentage of the sociodemographic variables and the endorsement of WI-7 items. Cronbach's α was calculated to examine internal consistency reliability of the WI-7. Internal consistency was further examined
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using phi correlation and point-biserial correlation to calculate the inter-item and item-total correlations. The differences in the total scores as well as the individual items of the WI-7 between the first and second administrations were examined using phi correlation, Cohen's kappa, Pearson correlation, intraclass correlation, and Wilcoxon's signed ranks test. WI-7 scores were further dichotomized into low vs. high scorers and comparisons between the first and second administrations were made using frequency distribution and McNemar test. In order to examine how the WI-7 relates to other factors, Pearson correlation, linear regression, and ordinal regression were conducted to examine the associations between WI-7 total score with sociodemographic variables, PHQ-15 total score, SDS scores, healthcare visits, and help-seeking experiences, where appropriate. The statistical package SPSS 15.0 for Windows was used for these analyses. In order to verify whether a 2-factor model or a 1-factor model of the WI-7 (Fink et al. [13]) fits our sample, the diagonally weighted least squares (DWLS) method was conducted using LISREL 8.80. Since the WI-7 items are categorical in nature, tetrachoric correlation matrix and asymptotic covariance matrix were estimated before fitting the model through DWLS. The following measures were evaluated to compare which of the two factor structures better fits the data: (i) Satorra–Bentler scaled chi-square (values should not be statistically significant); (ii) root mean square error of approximation (RMSEA; values lower than 0.10 indicate good fit, b0.05 indicate very good fit, and b0.01 indicate extremely good fit); (iii) expected crossvalidation index (ECVI; lower values indicate a closer fit); (iv) model consistent version of the Akaike's information criterion (CAIC; lower values indicate a better fit); (v) non-normed fit index (NNFI; values between 0.97 and 1.00 indicate good fit); (vi) comparative fit index (CFI; values between 0.97 and 1.00 indicate good fit); (vii) relative fit index (RFI; values closer to 1.00 indicate good fit); (viii) standardized root mean square residual (RMR; values lower than 0.10 indicate acceptable fit and values lower than 0.05 indicate good fit); and (ix) adjusted goodness of fit index (AGFI; values larger than 0.90 are considered a good fit). The results were evaluated based on an alpha level of 0.05 of a two-tailed test. Results
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Table 2 Sociodemographic profile of the sample and the mean of the 7-item Whiteley Index
Gender Male Female Age 15–24 25–34 35–44 45–54 55–65 Educational status Primary (Grade 1–6) Secondary (Grade 7–11) Post-secondary University or above Marital Status Single Married/cohabited Divorced/widowed Employment status Employed Unemployed Retired Full-time students Home-makers Family monthly income (HKD)a b$10,000 $10,000–$29,999 $30,000–$59,999 N$60,000 a
n
%
Mean (SD)
1404 1610
46.6 53.4
2.14 (1.90) 2.47 (1.99)
510 615 679 729 475
16.9 20.4 22.5 24.2 15.7
2.07 2.18 2.31 2.53 2.44
(1.73) (1.88) (1.93) (2.09) (2.06)
298 1324 352 1024
9.9 44.2 11.8 34.2
2.72 2.40 2.12 2.15
(2.23) (2.01) (1.83) (1.82)
1111 1772 112
37.1 59.2 3.7
2.16 (1.82) 2.38 (2.01) 2.92 (2.25)
1866 165 224 352 391
62.3 5.5 7.5 11.7 13.0
2.30 2.46 2.24 2.03 2.63
(1.95) (2.08) (1.95) (1.68) (2.12)
472 1376 677 284
16.8 49.0 24.1 10.1
2.68 2.38 2.10 2.14
(2.16) (1.99) (1.77) (1.82)
USD$1=HKD$7.8.
Intraclass correlation coefficient for measuring the consistency between the total scores of the first and second interviews was 0.76 (95% CI=0.69–0.81). Wilcoxon signed ranks test found no significant differences between the first and second administration of the WI-7 (Z=−1.15, p=.25), including when stratified by gender (male: Z=−1.14, p=.25) (female: Z=−0.64, p=.52). We further classified respondents who scored 3 or above and below 3 on the WI-7 as “high scorers” and “low scorers” respectively [21,22]. 47.6% (n=94) and 43.7% (n=87) of the respondents scored 3 or above for the first and second assessments respectively. The percentage of agreement between the first and second administrations was 79.9% (159 of 199 respondents). The difference in the proportion of high vs. low scorers among these matched pairs was not significant (McNemar test, p=.34).
Sample characteristics Association with sociodemographic variables The sociodemographic profile of the sample was representative of the Hong Kong population (Table 2). 46.6% and 53.4% of the respondents were male and female respectively. 17.0%, 20.4%, 22.6%, 24.2%, and 15.8% belonged to the age groups of 15–24 years, 25–34 years, 35–44 years, 45–54 years, and 55–65 years respectively. About half of the respondents had obtained secondary and post-secondary levels of education. The majority of the sample was married or cohabitating. Nearly two-thirds were employed.
The associations between sociodemographic variables and WI-7 total score were examined using linear regression. Older age (45–54 years old) (β=0.08, t=2.05, p=.04), female gender (β=−0.33, t=−4.24, pb.001), and lower monthly family income (β=−0.18, t=−3.71, pb.001) were associated with higher WI-7 score. Association with somatic symptoms
Frequency distribution of items The most commonly endorsed item was “worrying a lot about one's health” (55.7%), followed by “worrying about getting the disease oneself if it is brought to his/her attention” (48.7%) and “bothered by many different pains and aches” (33.9%) (Table 1). The least commonly endorsed item was “hard to believe the doctor when he/she tells you that there is nothing to worry about” (16.2%). Internal consistency and test–retest reliability Cronbach's α for the WI-7 was moderate at 0.73. The average inter-item correlation is 0.28, with the individual phi correlation coefficients ranging from 0.17 to 0.47. The average item-total correlation is 0.62, with the individual point-biserial correlation coefficients ranging from 0.52 to 0.67. Among the 199 re-assessed respondents, the individual item scores of the first and second interviews were significantly correlated (phi=0.46–0.56, pb.001). A moderate level of agreement was found for all the items between the two administrations, with Cohen's kappa ranging from 0.46 (“worrying about getting the disease oneself if it is brought to his/her attention”) to 0.56 (“thinking that there's something seriously wrong with one's body”). The average total WI-7 scores for the first and second interview were 2.65 (SD=2.10) and 2.51 (SD=2.27) respectively. These were strongly correlated at 0.76 (Pearson r, pb.001). Similar results were found when the data were stratified by gender (male: Pearson r=0.71, pb.001; female: Pearson r=0.79, pb.001).
Separate analyses were conducted for males and females when examining the effects of WI-7 on the endorsement of PHQ-15 symptoms. As there is one item about menstrual problem, the total score that females could obtain was 30 while for males was 28. WI-7 and PHQ-15 total scores were significantly correlated at 0.50 and 0.55 for males and females respectively (Pearson r, pb.001). When the two items about somatic distress on the WI-7 were removed, associations between PHQ-15 total score and the sum of the remaining five items on WI remained significant for males and females (results available upon request), indicating that health anxiety without somatic symptoms was still associated with more somatic distress. Association with impairment and healthcare visits Total WI-7 scores were significantly correlated with total SDS scores (Pearson r=0.40, pb.001) and all SDS subscale scores (Pearson r=0.33–0.35, pb.001). WI-7 total scores significantly predicted impairment as measured by the SDS total score and the four SDS subscale scores even after controlling for sociodemographic variables and PHQ-15 total score (SDS total score: β=0.83, t=10.18, pb.001; household responsibilities: β=0.20, t=8.04, pb.001; work/school: β=0.22, t=8.27, pb.001; close relationships: β=0.22, t=8.59, pb.001; social life: β=0.20, t=7.89, pb.001). WI-7 total scores explained a significant proportion of variance in SDS scores (R2=0.16, F(1, 3011)=557.52, pb.001). Total WI-7 scores and healthcare visits in the previous year were significantly correlated (Spearman's rho=0.32, pb.001). Higher WI-7 total scores significantly
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increased the likelihood of more frequent help-seeking in the previous one year (OR=1.20, Wald=68.11, pb.001) even after controlling for sociodemographic variables and somatic distress. Association with help-seeking experience In ordinal logistic regression analyses, we examined the association of the perceived helpfulness of doctors and level of satisfaction about doctors with WI-7 total scores. After controlling for sociodemographic variables, higher WI-7 total scores were significantly associated with both lower levels of perceived helpfulness (OR=1.28, Wald=172.70, pb.001) and satisfaction with their doctors (OR=1.26, Wald=158.00, pb.001). Confirmatory factor analysis A 1-factor model and a 2-factor model [13] were tested using confirmatory factor analysis. For the latter, items #2, 4, and 6 loaded on a factor that may be termed “illness worrying” and items #3, 5, and 7 loaded on another factor that may be called “illness conviction” (Table 1). The fit indices were listed in Table 3 for comparing these two models. Overall, the 2-factor model provides the best fit for the data, as it has a lower RMSEA, ECVI, Model CAIC, standardized RMR, as well as higher NNFI, CFI, RFI, and AGFI. The standardized estimates of factor loadings for both the 1-factor model and the 2-factor model are summarized in Table 1, which ranged from 0.59 to 0.87.
Discussion The present study is the first to examine the psychometric properties of the WI-7 and hence health anxiety and its correlates in a Chinese general population. It indicates that the Chinese WI-7 is reliable in several ways. First, its internal consistency (α=0.73) was satisfactory and slightly higher than in previous studies of the WI-7 in Western clinical (α=0.68) [3] and community (α=0.59) [15] samples. Second, the average item-total correlation (0.62) was satisfactory and stronger than those previously reported [3]. Third, the test–retest reliability results showed moderate agreement for all the individual items and total score of WI-7 as well as the proportion of high scorers in the first and second administrations of the WI-7. Our results also replicated findings of previous studies using the WI-7 or WI-14, and provide indirect evidence for external validity. Consistent with previous studies using the PHQ-15 or other measures of somatization in both clinical [13,18] and community populations [17], more WI-7 health anxiety was associated with more PHQ-15 somatic distress. It is worth noting that the association between PHQ-15 total score and WI-7 score remained significant even after excluding the two WI-7 items on somatic symptoms. Since somatic symptoms are non-specific and can occur in the absence of health anxiety [18], the WI-7 may help screen hypochondriacal from non-hypochondriacal somatizing patients [7]. In keeping with previous studies using the Whiteley Index, our results indicated that health anxiety was moderately associated with functional impairment [19] and increased healthcare visits [14,19,20]. This was so even after controlling for somatic distress, suggesting that to a certain extent “pure” health anxiety was associated with impairment and
increased health service use. In addition, we confirmed that individuals with health anxiety were more likely to perceive their doctors as less helpful and be less satisfied with the doctors [19,26]. This is the first study to examine the profile of health anxiety in a Chinese general population. The pattern of the three most commonly endorsed WI-7 items were largely consistent with a communitybased WI-14 study in Germany [4] and Canada [5] respectively. This cross-nationally similar frequency profile of health anxiety lends indirect support to the use of WI-7 in a Chinese population. The exact reasons for the higher frequency of each of the WI-7 items in Hong Kong than in the above Western communities remain to be examined. Our results on the associations with female gender, increased age, and low family monthly income were similar to a community-based study in Germany [4], though one clinical [18] and two community [1,5] studies found an association between male gender and health anxiety instead. The percentage of high scorers (40%) among our respondents was high when compared to those found in Western clinical studies [22,23]. It would thus be reasonable to believe that health anxiety is a common experience in Hong Kong. Using exploratory principal component analysis and a tertiary care sample, Pilowsky (1967) [2] found a 3-factor structure of the WI-14 (namely, bodily preoccupation, disease phobia, and disease conviction). However, subsequent factor analytic studies of the WI-14 were limited to clinical samples and the factorial structures were quite variable [5,7,13,27–31]. A clinical study in Denmark extracted the 7 items from the WI-14 using latent structure analysis before examining the factorial structure of the WI-7, and established high internal validity. This 7-item WI has also been compared with other factorial models that are comprised of 6 to 14 items loading on 1 to 3 latent variables in two other studies. While Conradt et al. (2006) [3] reported that WI-7 has the best fit among others, Asmundson et al. (2008) [5] claimed that the 6-item two-factor model was the best fit for the data. In our study we have compared both the 1-factor structure and the 2-factor structure of the WI-7, and the goodness of fit indices indicated that the latter provides a better fit for the data. It is noteworthy that most of the fit indices were very similar between these two models and most indices were satisfactory. Furthermore, the standardized factor loadings for each item in both 1-factor and 2-factor models were all above 0.59. The stable structure provides further support to the use of WI-7 in various cultural settings. The better fit revealed by the 2-factor model makes clinical sense in that illness worrying is generally the most common form of health anxiety encountered while illness conviction is a more marked form of health anxiety belief that is often accompanied by somatic distress. However, the similar values of the global fit indices do suggest that the various items pertaining to the constructs of disease fear, disease conviction, and bodily preoccupation or distress were overlapping [5,31]. The present study has several limitations that may provide leads for future research. First, since we examined a community sample in
Table 3 Confirmatory factor analysis of the 7-item Whiteley Index Factor structure
Satorra–Bentler scaled χ2 (p-value)
RMSEA
ECVI
Model CAIC
NNFI
CFI
RFI
Standardized RMR
AGFI
1-factora 2-factorb
424.97 (b 0.01) 109.71 (b 0.01)
0.1 0.07
0.02 0.01
551.1 226.85
0.96 0.98
0.97 0.99
0.96 0.98
0.08 0.07
0.96 0.98
RMSEA=Root Mean Square Error of Approximation. ECVI=Expected Cross-validation Index. Model CAIC=Model Consistent version of the Akaike's Information Criterion. NNFI=Non-Normed Fit Index. CFI=Comparative Fix Index. RFI=Relative Fit Index. Standardized RMR=Standardized Root Mean square Residual. AGFI=Adjusted Goodness of Fit Index. a 1-factor structure proposed by Fink et al. [13] with all the 7 items entered into the model. b 2-factor structure proposed by Fink et al. [13]: (1) illness worrying (“Do you worry a lot about your health”, “Do you often worry about the possibility that you have a serious illness”, and “If a disease is brought to your attention, do you worry about getting it yourself”); (2) illness conviction (“Is it hard for you to believe the doctor when he tells you there is nothing to worry about”, “Are you bothered by many different pains and aches”, and “Do you find that you are bothered by many different symptoms”).
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Hong Kong, the psychometric properties of the Chinese WI-7 in clinical and other Chinese settings remain to be established. Second, as we have administered the WI-7 through telephone (interviewer read out the questions and interviewee picked the answer himself/herself), our results may be different should the self-completed format of administration be used. Third, although Welch et al. (2009) [31] reported that the 5-point Likert scale version of the WI-7 [32] was not superior to the dichotomous response version, the former may be more suited for assessing the dimensional nature of health anxiety than the dichotomous response format we used [1]. Future research should compare the psychometric properties of these two versions. Fourth, although comorbidity between somatoform, depressive, and/or anxiety disorders was common [33], we did not examine psychological distress in order to determine whether health anxiety alone or comorbid mental disorder accounted for the poorer outcome of individuals with health anxiety. Finally, the WI-7 is brief and may not include certain facets of health anxiety that are covered in more detailed measurement tools or are common in the local Chinese population.
[14]
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[18]
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[21]
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Contents lists available at ScienceDirect
Journal of Psychosomatic Research
A general population study of the Chinese Whiteley-7 Index in Hong Kong Sing Lee a, b, c,⁎, King Lam Ng a, Yee Ling Ma a, Adley Tsang c, Kathleen P.S. Kwok c a b c
Department of Psychiatry, The Chinese University of Hong Kong, Hong Kong, China Department of Global Health and Social Medicine, Harvard Medical School, Boston, MA, USA Hong Kong Mood Disorders Center, The Chinese University of Hong Kong, Hong Kong, China
a r t i c l e
i n f o
Article history: Received 18 March 2011 Received in revised form 31 May 2011 Accepted 31 May 2011 Keywords: Chinese population Health anxiety Reliability Validity Whiteley Index
a b s t r a c t Objective: To examine the psychometric properties of the Chinese seven-item Whiteley Index (WI-7) in the general population of Hong Kong. Methods: A random community-based telephone survey of 3014 respondents aged 15–65 was conducted using a fully structured questionnaire that included the WI-7, 15-item Patient Health Questionnaire (PHQ15), Sheehan Disability Scale (SDS), and items about the frequency of health service use, perceived helpfulness of doctors, level of satisfaction with doctors, and sociodemographic variables. A sub-sample of 199 respondents was re-interviewed to assess test–retest reliability. Results: The WI-7 exhibited satisfactory internal consistency (Cronbach's α=0.73) and stable one-month test-retest reliability. The most commonly endorsed item was “worrying a lot about one's health” (55.7%), followed by “worrying about getting the disease oneself if it is brought to his/her attention” (48.7%) and “bothered by many different pains and aches” (33.9%). Age, gender, and monthly family income significantly predicted WI-7 score. Confirmatory factor analysis revealed that a 2-factor structure was superior to a 1-factor structure in fitting the data. WI-7 total score was positively associated with PHQ-15 somatic distress, SDS impairment, number of healthcare visits, lower levels of perceived helpfulness of doctors and of satisfaction with doctors. Conclusion: The Chinese WI-7 exhibits satisfactory reliability and internal validity in a general population. It is a promising tool for the empirical examination of health anxiety which is a common experience with a mostly typical epidemiological profile among Chinese people in Hong Kong. © 2011 Elsevier Inc. All rights reserved.
Introduction Health anxiety lies on a spectrum of intensity [1,2] and is common in both clinical [3] and community [4] settings. Even when not reaching the clinical diagnostic threshold of hypochondriasis, it can be impairing, cause difficult doctor–patient relationship, and increase healthcare cost [5–7]. Health anxiety is responsive to cognitivebehavioral therapy [8], but is often not assessed clinically. Moreover, mainstream epidemiological research usually does not examine health anxiety except for the diagnosis of hypochondriasis which is uncommon at a general population level [9]. These are despite the fact that a number of instruments are available for the dimensional assessment of health anxiety. Some of these instruments, such as the 29-item Illness Attitude Scales [10] and the 31-item Cognitions About Body And Health Questionnaire [11], may be too lengthy to administer in time-limited clinical and epidemiological settings. They also do not address certain ⁎ Corresponding author at: Hong Kong Mood Disorders Center, 7A, Block E, Staff Quarters, Prince of Wales Hospital, Shatin, N.T., Hong Kong, China. Tel.: +852 2144 5338; fax: +852 2144 5129. E-mail address: [email protected] (S. Lee). 0022-3999/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.jpsychores.2011.05.013
core features of health anxiety such as somatic symptoms and disease conviction [7]. The 14-item Whiteley Index (WI-14) is the first selfreport measure designed to assess health anxiety. It comprises of 14 items that assess the affective, cognitive and somatic components of hypochondriasis, namely bodily preoccupation, disease phobia, and disease conviction [2]. It has been widely used and shown to exhibit good internal consistency, test–retest reliability, convergent validity, and concurrent validity [7,12]. A shorter version, namely the 7-item Whiteley Index (WI-7), is also available and contains 7 of the original 14 items of the WI-14 [13]. It demonstrated excellent psychometric properties in primary care samples, with good sensitivity and specificity for screening DSM-IV somatization disorder and hypochondriasis respectively [3,13]. Two correlated and overlapping constructs, namely, illness worrying and illness conviction, are generally found to be embedded in the WI-7 in Western populations [13], but confirmatory factor analysis has yet to be conducted to examine whether this factor structure is applicable to other populations. Health anxiety is closely associated with somatization and increased healthcare visits in Western populations [5,7,14,15]. Although somatization [16] and doctor-shopping [17] are common in Hong Kong, there has been no community or clinical epidemiological study of health anxiety in Chinese and most other Asian populations. This may be due to
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the lack of a brief and suitable tool for assessing health anxiety in Chinese people. In fact, nearly all previous studies of the psychometric properties of the Whiteley Index were conducted in Western clinical samples [15,18–20]. The aim of the present study was to examine the psychometric properties of the Chinese WI-7 in the general population of Hong Kong. Method Sampling This two-stage study was approved by the research ethics committee of The Chinese University of Hong Kong. In the first stage, a random telephone survey of the general population aged between 15 and 65 years was conducted between September 2 and 22, 2009. As over 99% of the domestic households in Hong Kong have a telephone at home and very few of them have more than one telephone line [21], sampling telephone lines based on the updated residential telephone directory should generate a representative sample of households. In our study, 29,000 telephone numbers were randomly selected from the latest Residential Telephone Directory by computer and the last two digits were replaced by computer-generated random numbers to capture unlisted telephone numbers. A non-contact status was assigned to telephone numbers that could not be contacted after three attempts on different days, invalid telephone numbers generated by computers, fax numbers, non-residential numbers, and line busy (n=17,880). In each successfully contacted residential unit, only one person was interviewed. Overall, 11,120 calls were made that had successfully established contact with the household, of which the breakdown is as follows: no interviewee aged between 15 and 65 years in 1625 calls, people hung up immediately in 4004 calls, and rejected the interview in 2477 calls. Thus, 3014 interviews were successfully completed. Of the households that were successfully contacted and had interviewees within the age range, the participation rate was 54.9% (3014/[3014+2477]×100%). Informed verbal consent was obtained prior to each successfully completed interview, which took an average of 7.4 min (SD=1.9 min). The sample was weighted according to the gender distribution of different age groups in Hong Kong as reported by the Census and Statistics Department of the Hong Kong Government. With a 95% confidence level, the maximum sampling error was ±1.76%. In order to establish the test–retest reliability of the WI-7, a sub-sample of 199 respondents (6.6%) was conveniently drawn from those (n=1128) who had completed the first stage of the telephone survey and agreed to be contacted again for the second administration of the survey. They were re-interviewed by phone between 19 and 49 days (average=27.9 days) in the second stage of the study. Instruments An independent survey research organization, the Hong Kong Institute of Asia-Pacific Studies of The Chinese University of Hong Kong, was commissioned to conduct the survey. The interviewers were university students with 1–3 years of part-time experience in administering telephone survey interviews, including those on mental disorders. They were given a briefing session to familiarize themselves with the fully structured questionnaire used. The interview was conducted in Cantonese Chinese, the predominant dialect used in Hong Kong. The questionnaire included Chinese versions of the 15-item Patient Health Questionnaire (PHQ-15), WI-7, Sheehan Disability Scale (SDS), items probing the frequency of health service use, perceived helpfulness of doctors, level of satisfaction with doctors, and sociodemographic variables. The WI-7 allows a dichotomous choice of “yes” or “no” (Table 1). The 7 items were carefully translated by the lead author, an experienced bilingual clinician and researcher, and were found to be readily understood by Chinese speaking psychiatric patients and non-patients.
Table 1 The frequency distribution and factor loadings of the 7-item Whiteley Index Frequency of symptoms Total sample (n=3014) Whiteley 7 items (English)
n
%
Factor Factor loadings of loadings of a 1-factor model 2-factor modelb,c
1. Do you think there is something 662 22.0 0.72 seriously wrong with your body? 2. Do you worry a lot about your 1679 55.7 0.75 health? 487 16.2 0.59 3. Is it hard for you to believe the doctor when he or she tells you there is nothing to worry about? 762 25.3 0.80 4. Do you often worry about the possibility that you have a serious illness? 5. Are you bothered by many 1022 33.9 0.71 different pains and aches? 6. If a disease is brought to your 1468 48.7 0.60 attention (e.g. on TV, radio, the newspapers, or by someone you know), do you worry about getting it yourself? 7. Do you find that you are bothered 904 30.0 0.74 by many different symptoms?
0.80 0.61
0.87
0.79 0.67
0.81
a
Factor loadings of the 1-factor model in our sample. Factor loadings of the 2-factor model in our sample. Items #2, #4, and #6 were loaded on “illness worrying” factor; items #3, #5, and #7 were loaded on “illness conviction” factor. b c
A score of “1” was given for each “yes” response and the total score (range 0–7) was obtained additively [22,23]. Permission to use the Cantonese Chinese version of the PHQ-15 was obtained from Pfizer New York. The PHQ-15 asks respondents to rate how much they have been bothered by each of 15 symptoms during the past 4 weeks on a “0” (not bothered at all) to “2” (bothered a lot) scale, with the total score ranges from 0 to 30 [24]. The Chinese PHQ-15 exhibited satisfactory reliability and validity in the same sample of respondents who participated in the present study [16]. The SDS was used to assess role impairment on four domains of life in the past four weeks, which include household responsibilities (“doing housework, such as cleaning and grocery shopping”), work/school (“the ability to work, such as working, studying, or taking exams”), close relationships (“the ability to form and maintain close relationships with other people, such as romantic partner, family members, or close friends”), and social life (“the ability to form social relationship”), all of which were rated on a scale of 0 to 10 (none (0), mild (1–3), moderate (4–6), severe (7–9) and very severe (10)) [25]. The SDS is widely used in both Western and Chinese community psychiatric surveys [16]. Frequency of health service use was assessed by asking “in the previous year, how often on average did you seek help from health professionals?” There are seven response categories ranging from “nil in the previous year” to “once a week or more”. Perceived helpfulness of doctors was assessed on a scale from 0 to 5, with “0” representing “completely not helpful” and “5” representing “very helpful”. Level of satisfaction with doctors was assessed similarly on a scale from 0 to 5, with “0” representing “strongly dissatisfied” to “5” representing “strongly satisfied”. Statistical analysis Cross-tabulations were conducted to estimate the percentage of the sociodemographic variables and the endorsement of WI-7 items. Cronbach's α was calculated to examine internal consistency reliability of the WI-7. Internal consistency was further examined
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using phi correlation and point-biserial correlation to calculate the inter-item and item-total correlations. The differences in the total scores as well as the individual items of the WI-7 between the first and second administrations were examined using phi correlation, Cohen's kappa, Pearson correlation, intraclass correlation, and Wilcoxon's signed ranks test. WI-7 scores were further dichotomized into low vs. high scorers and comparisons between the first and second administrations were made using frequency distribution and McNemar test. In order to examine how the WI-7 relates to other factors, Pearson correlation, linear regression, and ordinal regression were conducted to examine the associations between WI-7 total score with sociodemographic variables, PHQ-15 total score, SDS scores, healthcare visits, and help-seeking experiences, where appropriate. The statistical package SPSS 15.0 for Windows was used for these analyses. In order to verify whether a 2-factor model or a 1-factor model of the WI-7 (Fink et al. [13]) fits our sample, the diagonally weighted least squares (DWLS) method was conducted using LISREL 8.80. Since the WI-7 items are categorical in nature, tetrachoric correlation matrix and asymptotic covariance matrix were estimated before fitting the model through DWLS. The following measures were evaluated to compare which of the two factor structures better fits the data: (i) Satorra–Bentler scaled chi-square (values should not be statistically significant); (ii) root mean square error of approximation (RMSEA; values lower than 0.10 indicate good fit, b0.05 indicate very good fit, and b0.01 indicate extremely good fit); (iii) expected crossvalidation index (ECVI; lower values indicate a closer fit); (iv) model consistent version of the Akaike's information criterion (CAIC; lower values indicate a better fit); (v) non-normed fit index (NNFI; values between 0.97 and 1.00 indicate good fit); (vi) comparative fit index (CFI; values between 0.97 and 1.00 indicate good fit); (vii) relative fit index (RFI; values closer to 1.00 indicate good fit); (viii) standardized root mean square residual (RMR; values lower than 0.10 indicate acceptable fit and values lower than 0.05 indicate good fit); and (ix) adjusted goodness of fit index (AGFI; values larger than 0.90 are considered a good fit). The results were evaluated based on an alpha level of 0.05 of a two-tailed test. Results
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Table 2 Sociodemographic profile of the sample and the mean of the 7-item Whiteley Index
Gender Male Female Age 15–24 25–34 35–44 45–54 55–65 Educational status Primary (Grade 1–6) Secondary (Grade 7–11) Post-secondary University or above Marital Status Single Married/cohabited Divorced/widowed Employment status Employed Unemployed Retired Full-time students Home-makers Family monthly income (HKD)a b$10,000 $10,000–$29,999 $30,000–$59,999 N$60,000 a
n
%
Mean (SD)
1404 1610
46.6 53.4
2.14 (1.90) 2.47 (1.99)
510 615 679 729 475
16.9 20.4 22.5 24.2 15.7
2.07 2.18 2.31 2.53 2.44
(1.73) (1.88) (1.93) (2.09) (2.06)
298 1324 352 1024
9.9 44.2 11.8 34.2
2.72 2.40 2.12 2.15
(2.23) (2.01) (1.83) (1.82)
1111 1772 112
37.1 59.2 3.7
2.16 (1.82) 2.38 (2.01) 2.92 (2.25)
1866 165 224 352 391
62.3 5.5 7.5 11.7 13.0
2.30 2.46 2.24 2.03 2.63
(1.95) (2.08) (1.95) (1.68) (2.12)
472 1376 677 284
16.8 49.0 24.1 10.1
2.68 2.38 2.10 2.14
(2.16) (1.99) (1.77) (1.82)
USD$1=HKD$7.8.
Intraclass correlation coefficient for measuring the consistency between the total scores of the first and second interviews was 0.76 (95% CI=0.69–0.81). Wilcoxon signed ranks test found no significant differences between the first and second administration of the WI-7 (Z=−1.15, p=.25), including when stratified by gender (male: Z=−1.14, p=.25) (female: Z=−0.64, p=.52). We further classified respondents who scored 3 or above and below 3 on the WI-7 as “high scorers” and “low scorers” respectively [21,22]. 47.6% (n=94) and 43.7% (n=87) of the respondents scored 3 or above for the first and second assessments respectively. The percentage of agreement between the first and second administrations was 79.9% (159 of 199 respondents). The difference in the proportion of high vs. low scorers among these matched pairs was not significant (McNemar test, p=.34).
Sample characteristics Association with sociodemographic variables The sociodemographic profile of the sample was representative of the Hong Kong population (Table 2). 46.6% and 53.4% of the respondents were male and female respectively. 17.0%, 20.4%, 22.6%, 24.2%, and 15.8% belonged to the age groups of 15–24 years, 25–34 years, 35–44 years, 45–54 years, and 55–65 years respectively. About half of the respondents had obtained secondary and post-secondary levels of education. The majority of the sample was married or cohabitating. Nearly two-thirds were employed.
The associations between sociodemographic variables and WI-7 total score were examined using linear regression. Older age (45–54 years old) (β=0.08, t=2.05, p=.04), female gender (β=−0.33, t=−4.24, pb.001), and lower monthly family income (β=−0.18, t=−3.71, pb.001) were associated with higher WI-7 score. Association with somatic symptoms
Frequency distribution of items The most commonly endorsed item was “worrying a lot about one's health” (55.7%), followed by “worrying about getting the disease oneself if it is brought to his/her attention” (48.7%) and “bothered by many different pains and aches” (33.9%) (Table 1). The least commonly endorsed item was “hard to believe the doctor when he/she tells you that there is nothing to worry about” (16.2%). Internal consistency and test–retest reliability Cronbach's α for the WI-7 was moderate at 0.73. The average inter-item correlation is 0.28, with the individual phi correlation coefficients ranging from 0.17 to 0.47. The average item-total correlation is 0.62, with the individual point-biserial correlation coefficients ranging from 0.52 to 0.67. Among the 199 re-assessed respondents, the individual item scores of the first and second interviews were significantly correlated (phi=0.46–0.56, pb.001). A moderate level of agreement was found for all the items between the two administrations, with Cohen's kappa ranging from 0.46 (“worrying about getting the disease oneself if it is brought to his/her attention”) to 0.56 (“thinking that there's something seriously wrong with one's body”). The average total WI-7 scores for the first and second interview were 2.65 (SD=2.10) and 2.51 (SD=2.27) respectively. These were strongly correlated at 0.76 (Pearson r, pb.001). Similar results were found when the data were stratified by gender (male: Pearson r=0.71, pb.001; female: Pearson r=0.79, pb.001).
Separate analyses were conducted for males and females when examining the effects of WI-7 on the endorsement of PHQ-15 symptoms. As there is one item about menstrual problem, the total score that females could obtain was 30 while for males was 28. WI-7 and PHQ-15 total scores were significantly correlated at 0.50 and 0.55 for males and females respectively (Pearson r, pb.001). When the two items about somatic distress on the WI-7 were removed, associations between PHQ-15 total score and the sum of the remaining five items on WI remained significant for males and females (results available upon request), indicating that health anxiety without somatic symptoms was still associated with more somatic distress. Association with impairment and healthcare visits Total WI-7 scores were significantly correlated with total SDS scores (Pearson r=0.40, pb.001) and all SDS subscale scores (Pearson r=0.33–0.35, pb.001). WI-7 total scores significantly predicted impairment as measured by the SDS total score and the four SDS subscale scores even after controlling for sociodemographic variables and PHQ-15 total score (SDS total score: β=0.83, t=10.18, pb.001; household responsibilities: β=0.20, t=8.04, pb.001; work/school: β=0.22, t=8.27, pb.001; close relationships: β=0.22, t=8.59, pb.001; social life: β=0.20, t=7.89, pb.001). WI-7 total scores explained a significant proportion of variance in SDS scores (R2=0.16, F(1, 3011)=557.52, pb.001). Total WI-7 scores and healthcare visits in the previous year were significantly correlated (Spearman's rho=0.32, pb.001). Higher WI-7 total scores significantly
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increased the likelihood of more frequent help-seeking in the previous one year (OR=1.20, Wald=68.11, pb.001) even after controlling for sociodemographic variables and somatic distress. Association with help-seeking experience In ordinal logistic regression analyses, we examined the association of the perceived helpfulness of doctors and level of satisfaction about doctors with WI-7 total scores. After controlling for sociodemographic variables, higher WI-7 total scores were significantly associated with both lower levels of perceived helpfulness (OR=1.28, Wald=172.70, pb.001) and satisfaction with their doctors (OR=1.26, Wald=158.00, pb.001). Confirmatory factor analysis A 1-factor model and a 2-factor model [13] were tested using confirmatory factor analysis. For the latter, items #2, 4, and 6 loaded on a factor that may be termed “illness worrying” and items #3, 5, and 7 loaded on another factor that may be called “illness conviction” (Table 1). The fit indices were listed in Table 3 for comparing these two models. Overall, the 2-factor model provides the best fit for the data, as it has a lower RMSEA, ECVI, Model CAIC, standardized RMR, as well as higher NNFI, CFI, RFI, and AGFI. The standardized estimates of factor loadings for both the 1-factor model and the 2-factor model are summarized in Table 1, which ranged from 0.59 to 0.87.
Discussion The present study is the first to examine the psychometric properties of the WI-7 and hence health anxiety and its correlates in a Chinese general population. It indicates that the Chinese WI-7 is reliable in several ways. First, its internal consistency (α=0.73) was satisfactory and slightly higher than in previous studies of the WI-7 in Western clinical (α=0.68) [3] and community (α=0.59) [15] samples. Second, the average item-total correlation (0.62) was satisfactory and stronger than those previously reported [3]. Third, the test–retest reliability results showed moderate agreement for all the individual items and total score of WI-7 as well as the proportion of high scorers in the first and second administrations of the WI-7. Our results also replicated findings of previous studies using the WI-7 or WI-14, and provide indirect evidence for external validity. Consistent with previous studies using the PHQ-15 or other measures of somatization in both clinical [13,18] and community populations [17], more WI-7 health anxiety was associated with more PHQ-15 somatic distress. It is worth noting that the association between PHQ-15 total score and WI-7 score remained significant even after excluding the two WI-7 items on somatic symptoms. Since somatic symptoms are non-specific and can occur in the absence of health anxiety [18], the WI-7 may help screen hypochondriacal from non-hypochondriacal somatizing patients [7]. In keeping with previous studies using the Whiteley Index, our results indicated that health anxiety was moderately associated with functional impairment [19] and increased healthcare visits [14,19,20]. This was so even after controlling for somatic distress, suggesting that to a certain extent “pure” health anxiety was associated with impairment and
increased health service use. In addition, we confirmed that individuals with health anxiety were more likely to perceive their doctors as less helpful and be less satisfied with the doctors [19,26]. This is the first study to examine the profile of health anxiety in a Chinese general population. The pattern of the three most commonly endorsed WI-7 items were largely consistent with a communitybased WI-14 study in Germany [4] and Canada [5] respectively. This cross-nationally similar frequency profile of health anxiety lends indirect support to the use of WI-7 in a Chinese population. The exact reasons for the higher frequency of each of the WI-7 items in Hong Kong than in the above Western communities remain to be examined. Our results on the associations with female gender, increased age, and low family monthly income were similar to a community-based study in Germany [4], though one clinical [18] and two community [1,5] studies found an association between male gender and health anxiety instead. The percentage of high scorers (40%) among our respondents was high when compared to those found in Western clinical studies [22,23]. It would thus be reasonable to believe that health anxiety is a common experience in Hong Kong. Using exploratory principal component analysis and a tertiary care sample, Pilowsky (1967) [2] found a 3-factor structure of the WI-14 (namely, bodily preoccupation, disease phobia, and disease conviction). However, subsequent factor analytic studies of the WI-14 were limited to clinical samples and the factorial structures were quite variable [5,7,13,27–31]. A clinical study in Denmark extracted the 7 items from the WI-14 using latent structure analysis before examining the factorial structure of the WI-7, and established high internal validity. This 7-item WI has also been compared with other factorial models that are comprised of 6 to 14 items loading on 1 to 3 latent variables in two other studies. While Conradt et al. (2006) [3] reported that WI-7 has the best fit among others, Asmundson et al. (2008) [5] claimed that the 6-item two-factor model was the best fit for the data. In our study we have compared both the 1-factor structure and the 2-factor structure of the WI-7, and the goodness of fit indices indicated that the latter provides a better fit for the data. It is noteworthy that most of the fit indices were very similar between these two models and most indices were satisfactory. Furthermore, the standardized factor loadings for each item in both 1-factor and 2-factor models were all above 0.59. The stable structure provides further support to the use of WI-7 in various cultural settings. The better fit revealed by the 2-factor model makes clinical sense in that illness worrying is generally the most common form of health anxiety encountered while illness conviction is a more marked form of health anxiety belief that is often accompanied by somatic distress. However, the similar values of the global fit indices do suggest that the various items pertaining to the constructs of disease fear, disease conviction, and bodily preoccupation or distress were overlapping [5,31]. The present study has several limitations that may provide leads for future research. First, since we examined a community sample in
Table 3 Confirmatory factor analysis of the 7-item Whiteley Index Factor structure
Satorra–Bentler scaled χ2 (p-value)
RMSEA
ECVI
Model CAIC
NNFI
CFI
RFI
Standardized RMR
AGFI
1-factora 2-factorb
424.97 (b 0.01) 109.71 (b 0.01)
0.1 0.07
0.02 0.01
551.1 226.85
0.96 0.98
0.97 0.99
0.96 0.98
0.08 0.07
0.96 0.98
RMSEA=Root Mean Square Error of Approximation. ECVI=Expected Cross-validation Index. Model CAIC=Model Consistent version of the Akaike's Information Criterion. NNFI=Non-Normed Fit Index. CFI=Comparative Fix Index. RFI=Relative Fit Index. Standardized RMR=Standardized Root Mean square Residual. AGFI=Adjusted Goodness of Fit Index. a 1-factor structure proposed by Fink et al. [13] with all the 7 items entered into the model. b 2-factor structure proposed by Fink et al. [13]: (1) illness worrying (“Do you worry a lot about your health”, “Do you often worry about the possibility that you have a serious illness”, and “If a disease is brought to your attention, do you worry about getting it yourself”); (2) illness conviction (“Is it hard for you to believe the doctor when he tells you there is nothing to worry about”, “Are you bothered by many different pains and aches”, and “Do you find that you are bothered by many different symptoms”).
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Hong Kong, the psychometric properties of the Chinese WI-7 in clinical and other Chinese settings remain to be established. Second, as we have administered the WI-7 through telephone (interviewer read out the questions and interviewee picked the answer himself/herself), our results may be different should the self-completed format of administration be used. Third, although Welch et al. (2009) [31] reported that the 5-point Likert scale version of the WI-7 [32] was not superior to the dichotomous response version, the former may be more suited for assessing the dimensional nature of health anxiety than the dichotomous response format we used [1]. Future research should compare the psychometric properties of these two versions. Fourth, although comorbidity between somatoform, depressive, and/or anxiety disorders was common [33], we did not examine psychological distress in order to determine whether health anxiety alone or comorbid mental disorder accounted for the poorer outcome of individuals with health anxiety. Finally, the WI-7 is brief and may not include certain facets of health anxiety that are covered in more detailed measurement tools or are common in the local Chinese population.
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