Kok-Yong Fong

The impact of diabetes mellitus and other chronic medical conditions on health-related Quality of Life: Is the whole greater than the sum of its parts?

BackgroundDiabetes mellitus (DM) is an important public health concern, the impact of which is increased by the high prevalence of co-existing chronic medical conditions among subjects with DM. The aims of this study were therefore to (1) evaluate the impact of DM and co-existing chronic medical conditions on health-related quality of life (HRQoL) (which could be additive, synergistic or subtractive); (2) to determine the extent to which the SF-6D (a single-index preference measure) captures the multidimensional information provided by the SF-36 (a profile measure).MethodsUsing data from a cross-sectional, population-based survey of Chinese, Malay and Indians in Singapore, we developed 9 separate multiple linear regression models, with each SF-36 scale or SF-6D index score being the dependent variable for one model. The influence of DM and a second chronic medical condition (hypertension (HTN), heart disease (HD), musculoskeletal illnesses (MS)) and their interactions were studied after adjusting for the influence of potential confounding variables.ResultsAmong 5,224 subjects, the prevalence of DM, HTN, HD and MS were 5.9%, 10.7%, 2.4% and 26.6% respectively. DM lowered SF-36 scores by more than 2 points on 3 SF-36 scales and lowered SF-6D scores by 0.03 points. Subjects with DM and HTN, DM and HD or DM and MS experienced further lowering of SF-36 scores exceeding 2 points on at least 6 scales and further lowering of SF-6D scores by 0.05, 0.08 and 0.10 points respectively. Generally, DM and co-existing medical conditions exerted additive effects on HRQoL, with the exception of DM and heart disease, where a subtractive effect was noted. SF-6D index scores generally reflected the patterns of influence of DM and chronic medical conditions on SF-36 scores.ConclusionDM and chronic medical conditions generally reduced HRQoL in this multiethnic general population in an additive, rather than synergistic or subtractive fashion. In this study, the SF-6D was a reasonably good summary measure for the SF-36.

Do English and Chinese EQ-5D versions demonstrate measurement equivalence? an exploratory study

BackgroundAlthough multiple language versions of health-related quality of life instruments are often used interchangeably in clinical research, the measurement equivalence of these versions (especially using alphabet vs pictogram-based languages) has rarely been assessed. We therefore investigated the measurement equivalence of English and Chinese versions of the EQ-5D, a widely used utility-based outcome instrument.MethodsIn a cross-sectional study, either EQ-5D version was administered to consecutive outpatients with rheumatic diseases. Measurement equivalence of EQ-5D item responses and utility and visual analog scale (EQ-VAS) scores between these versions was assessed using multiple regression models (with and without adjusting for potential confounding variables), by comparing the 95% confidence interval (95%CI) of score differences between these versions with pre-defined equivalence margins. An equivalence margin defined a magnitude of score differences (10% and 5% of entire score ranges for item responses and utility/EQ-VAS scores, respectively) which was felt to be clinically unimportant.ResultsSixty-six subjects completed the English and 48 subjects the Chinese EQ-5D. The 95%CI of the score differences between these versions overlapped with but did not fall completely within pre-defined equivalence margins for 4 EQ-5D items, utility and EQ-VAS scores. For example, the 95%CI of the adjusted score difference between these EQ-5D versions was -0.14 to +0.03 points for utility scores and -11.6 to +3.3 points for EQ-VAS scores (equivalence margins of -0.05 to +0.05 and -5.0 to +5.0 respectively).ConclusionThese data provide promising evidence for the measurement equivalence of English and Chinese EQ-5D versions.

The equivalence of English and Chinese SF-36 versions in bilingual Singapore Chinese.

Objective: To assess the equivalence of English and Chinese versions of the SF-36. Methods: Using a crossover design with block randomisation and stratification by age, identical English or Chinese questionnaires containing the English (UK) and Chinese (HK) SF-36 versions were administered 3–16 days apart to 168 free-living, bilingual, ethnic Chinese volunteers in Singapore. Item level equivalence of both versions was assessed by comparing item means and orderings within each scale. Scale level equivalence was assessed by comparing internal consistency (Cronbachs α), results of factor analysis and mean scale scores (using paired t-tests and intra-class correlations). Results: Item and scale level comparisons supported the equivalence of both versions. For both the versions, item means, item ordering and Cronbachs α were similar, and factor analysis yielded two factors with similar factor loadings. There was no clinically important difference in mean scale scores for seven of eight scales, and intra-class correlations were excellent/good for five scales (0.69–0.77) and moderate for three scales (0.55–0.57). Conclusion: English (UK) and Chinese (HK) SF-36 versions are equivalent in bilingual Singapore Chinese. Our data suggest that SF-36 scores from English- and Chinese-speaking subjects may be combined in studies using the SF-36, increasing the power and representativeness of such studies.

The association of body mass index with health-related quality of life: an exploratory study in a multiethnic Asian population

OBJECTIVES To evaluate the association between body mass index (BMI) and health-related quality of life (HRQoL) in a multiethnic Asian population in Singapore, and to explore if the World Health Organization (WHO) recommendation of alternative BMI cutoffs for Asians could be further strengthened by evidence of higher risk of impaired HRQoL using these criteria. METHODS Consenting English, Chinese, Malay and Tamil-speaking primary care patients (age >or= 21 years) were interviewed using English/their respective mother tongue versions of the EQ-5D/EQ-VAS, Health Utilities Index (HUI2 & HUI3) and the SF-6D. We first evaluated the relationship between BMI and HRQoL (overall and individual attributes for each instrument) using multiple linear/logistic regression (where appropriate) to adjust for factors known to affect HRQoL. We next reorganized BMI into five categories (reflecting the differences in cutoffs between International/Asian classifications) and evaluated if median HRQoL scores were significantly different across these categories. RESULTS Among 411 participants [response rate: 87%; median age: 51 years; obese: 19% (International); 33% (Asian)], after adjusting for sociodemographic and other factors, a tendency for underweight and obese subjects to report lower overall HRQoL scores was observed for most instruments. At the individual attribute level, obese subjects reported significantly lower HUI2 pain scores (regression coefficient: -0.035, P = 0.029) and greater odds of reporting problems for SF-6D role-limitations (odds ratio: 2.9, P = 0.005). Median overall HRQoL scores were not significantly different across the five BMI categories. CONCLUSION Consistent with available studies, obese subjects reported worse HRQoL than normal-weight subjects. That underweight subjects also reported worse HRQoL is interesting and requires confirmation. HRQoL was similar in Asians using either WHO criteria.

Pulmonary haemorrhage, pulmonary infarction, and the lupus anticoagulant.

A patient with systemic lupus erythematosus developed pulmonary haemorrhage and pulmonary infarction as rare initial manifestations of her disease. The latter was associated with the presence of the circulating lupus anticoagulant. She recovered with pulse doses of methylprednisolone and plasmapheresis. Anticoagulants were not administered.

A Study on Indirect and Intangible Costs for Patients with Knee Osteoarthritis in Singapore

OBJECTIVES To estimate indirect costs through human capital approach and intangible costs through willingness-to-pay (WTP), and identify factors potentially affecting these costs in multiethnic Asian patients with knee osteoarthritis (OA). METHODS Data were collected through face-to-face interviews among knee OA patients. Human capital approach was used to estimate indirect costs by multiplying: 1) days of absence from work because of OA, with average earnings per capita per day for working patients; or 2) productivity loss with the market price of housekeeping for retirees/homemakers. A closed-ended iterative bidding contingent valuation method was used to elicit willingness-to-pay for a hypothetical cure of OA as a proxy for intangible costs. Mann-Whitney U or Kruskal-Wallis H-tests were performed in univariate analyzes, and linear regression in multivariate analyses. RESULTS Indirect costs per year and intangible costs were estimated at US

The Impact of Health Literacy on Health-Related Quality of Life (HRQoL) and Utility Assessment among Patients with Rheumatic Diseases

1008 and US

Are English- and Chinese-language versions of the SF-6D equivalent? A comparison from a population-based study.

1200, accounting for 2.8% and 3.3% of annual household income, respectively. The indirect costs were significantly higher for male or working patients, while intangible costs were higher for Chinese, working patients, with higher income, or worse global well-being. CONCLUSION This study demonstrated that eliciting indirect costs through human capital approach and intangible costs through WTP are acceptable and feasible in Asian patients with knee OA. Besides the direct costs, the indirect and intangible costs for the OA patients could be substantial.

Does being bilingual in English and Chinese influence responses to Quality-of-Life scales?

OBJECTIVES The objective of this study was to investigate the impact of health literacy (HL) on health-related quality of life (HRQoL) and utility assessment among patients with rheumatic diseases. METHODS HL was measured by the rapid estimate of adult literacy in medicine (REALM) and was characterized as low or adequate. HRQoL and utility scores were assessed using the SF-36, SF-6D, and EQ-5D. Comparisons of sociodemographics and HRQoL in patients with low or adequate HL were made using t test, chi-square, or Mann-Whitney U tests. Spearmans correlation and partial correlations were used to study the relationship between HL, HRQoL, and utility scores, with significant correlations further explored using multiple linear regression models. RESULTS Data were analyzed from 199 subjects. Patients with adequate HL had significantly higher education levels, better dwelling status, lower disease activity, and better physical functioning (PF). There was a significant although weak correlation between HL level and PF. After adjustment, HL level was shown to independently explain 3.7% of the variance in the PF score. Nevertheless, there was no impact of HL on utility assessment or other HRQoL domains. CONCLUSION HL did not impact HRQoL in general, but was found to have a weak impact on the PF of patients with rheumatic diseases.

Validity, Feasibility and Acceptability of Time Trade-Off and Standard Gamble Assessments in Health Valuation Studies: A Study in a Multiethnic Asian Population in Singapore

OBJECTIVE The goal of this study was to assess the equivalence of English- and Chinese-language versions of the SF-6D (a 6-dimensional health classification system based on the 36-Item Short Form Health Survey) using a model of equivalence proposed previously. METHODS We analyzed data from a previously published, cross-sectional, population-based survey of ethnic Chinese in Singapore, using linear regression models to adjust for the influence of potential confounding variables. Based on equivalence clinical trial methods, measurement (ie, scale) and item equivalence were assessed by comparing 90% CIs of differences in scores due to language with predefined equivalence margins, that corresponded to the minimum clinically important difference for SF-6D utility and item scores. RESULTS Data from 2,558 respondents (aged 21-65 years; 48.8% completed the English-language version) were analyzed. The utility scores of respondents using the English- or Chinese-language versions of the SF-6D had similar distribution patterns, with a mean (SD) utility score of 0.8 (0.12). Adjusted 90% CIs for differences in utility and item scores due to language fell within predefined equivalence margins, suggesting measurement and item level equivalence. The 90% CI for scale scores was -0.0089 to 0.0065 (range, 0.0154; equivalence margin, 0.033); the 90% CI for item scores varied from -0.0046 to -0.0020 (range, 0.0026; equivalence margin, 0.0036) for vitality to -0.0024 to 0.0037 (range, 0.0061; equivalence margin, 0.0088) for social functioning. Functional equivalence was suggested because the various aspects of equivalence proposed previously were demonstrated in this study. CONCLUSIONS English- and Chinese-language versions of the SF-6D demonstrated item, measurement, and functional equivalence in this population-based study comparing 2 widely used languages with very different linguistic structures. This suggests that English and Chinese SF-6D scores can be pooled, thus increasing the representativeness and power of studies using the SF-6D, and providing a basis for studies to value health by obtaining SF-6D utility scores in Asian populations.