Rheumatology Advance Access originally published online on June 24, 2007
Rheumatology 2007 46(9):1441-1444; doi:10.1093/rheumatology/kem150
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Is gout associated with reduced quality of life? A case-control study
Academic Rheumatology, University of Nottingham, UK.
Correspondence to: Edward Roddy, Primary Care Musculoskeletal Research Centre, Primary Care Sciences, Keele University, Staffordshire ST5 5BG. E-mail: e.roddy{at}cphc.keele.ac.uk
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Abstract |
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Objectives. To compare quality of life (QOL) between gout cases and controls in a primary care population and to investigate whether impaired QOL in gout is secondary to co-morbid factors or to intrinsic factors related to gout itself.
Methods. A postal questionnaire was sent to all adults aged over 30 yrs registered with two general practices. The questionnaire assessed a history of gout (doctor diagnosed, or episodes suggestive of acute crystal synovitis) and medical and musculoskeletal co-morbidities. QOL was assessed using the WHOQoL-Bref instrument. Possible cases of gout attended for clinical assessment where the diagnosis was verified on clinical grounds. Overall QOL, satisfaction with health and QOL across four domains were compared between gout cases and controls and then entered into a linear regression model adjusting for gout, age, gender, body mass index and medical and musculoskeletal co-morbidities.
Results. Of 13 684 questionnaires mailed, 3082 completed questionnaires were returned (23%). From 289 suggested cases of gout, 137 cases were confirmed by clinical assessment. Compared with controls, cases had impaired overall QOL (15.67 vs 16.41, P = 0.003), satisfaction with health (13.16 vs 14.45, P < 0.001) and physical health-related QOL (14.08 vs 15.95, P < 0.001). On multi-variate analysis, gout remained associated with impaired physical health-related QOL (ß = –0.059, P = 0.001) but not overall QOL (ß = –0.024, P = 0.198) or satisfaction with health (ß = –0.028, P = 0.142).
Conclusions. Gout associates with poor overall QOL mainly resulting from associated co-morbidity. Physical health-related QOL, however, remains impaired after adjustment for co-morbidities.
KEY WORDS: Gout, Quality of life, General practice
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Introduction |
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Gout is one of the most prevalent causes of inflammatory arthritis affecting 1–2% of adults in the UK [1]. It is the most common cause of inflammatory arthritis in men with a male: female ratio of 3–5:1[1–3]. In contrast to the other common inflammatory arthritides, gout is largely managed in primary care in the UK. Gout is considered to be the most painful form of acute arthritis, but it also causes chronic arthropathy and associates with renal disease, cardiovascular co-morbidity [1, 4] and osteoarthritis (OA) [5–7]. Hyperuricaemia and primary gout are part of the metabolic syndrome so co-morbidity associated with obesity, hypertension, hyperlipidaemia and insulin resistance is common; diuretic therapy and chronic renal impairment are the main causes of secondary gout. Surprisingly, little is known of the impact of gout on quality of life (QOL). Two studies of QOL in patients with severe gout managed in secondary care demonstrated impaired QOL compared with reference values for the general population [8, 9]. However, such hospital-based populations are likely to include a more severe spectrum of disease than in primary care, limiting the generalizability of these results to the majority of gout sufferers in the community. One Dutch population-based cohort study found impaired QOL in gout patients compared with controls without musculoskeletal conditions, but there was no adjustment for the significant co-morbidity associated with gout [10].
The aims of this study were: (i) to examine whether gout is associated with impaired QOL compared to controls in a primary care population and (ii) to investigate whether any differences in QOL between gout cases and controls are secondary to co-morbid factors or result from intrinsic factors related to gout itself.
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Methods |
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The study was undertaken in two general practices in Nottingham and comprised two phases: (i) a postal questionnaire survey and (ii) a face-to-face clinical assessment. The study was approved by Nottingham Local Research Ethics Committee 2. Written consent was obtained from participants who attended for clinical assessment.
Postal questionnaire
Each practice drew up a list of all registered adults over the age of 30 yrs excluding those with a history of major psychiatric disease, dementia or recently diagnosed malignancy. Practice databases recorded 
400 patients with gout. A questionnaire was then mailed to all listed individuals with a pre-paid envelope included for their reply. A single questionnaire mailing was undertaken. Possible cases of gout were identified by two questions:
- ‘Have you ever been diagnosed with or suffered from gout?’
- ‘Have you ever suffered from an acute attack of arthritis that was severely painful, was associated with a red and swollen joint, came on suddenly reaching its peak severity within 24 h and then went away completely within 3 weeks?’ (i.e. a typical attack of crystal synovitis).
Use of allopurinol and diuretics were requested in addition to recording of standard demographic information, weight and height.
QOL was measured using the WHO-QoL Bref instrument [11]. This instrument assesses overall QOL with two questions:
- ‘How would you rate your quality of life?’
- ‘How satisfied are you with your health?’
Twenty-four further questions relate to four individual domains: physical (seven questions), psychological (six questions), social (three questions) and environment (eight questions).
Self-reported history of the following medical co-morbidities was requested: hypertension, hyperlipidaemia, diabetes mellitus, renal failure or dialysis, myocardial infarction (MI), angina, cerebrovascular accident (CVA) and transient ischaemic attack (TIA). Details of musculoskeletal co-morbidity were also requested, specifically the presence of pain within the last year in and around the knee that occurred on most days for at least a month [12], self-reported nodal OA [13], history of knee or hip replacement and self-reported rheumatoid arthritis (RA) or ankylosing spondylitis (AS).
Clinical assessment
All subjects reporting a previous diagnosis of gout or a history of acute self-limiting attacks of painful, red, swollen joints in their questionnaire (potential cases) were invited to attend a clinical assessment. At this visit, the subject's joint problems were reviewed by a single physician with special training in gout (E.R.) and the most likely diagnosis was made on clinical grounds. Where uncertainty existed over the diagnosis in individual cases, the case was discussed between two authors (E.R. and M.D.). The diagnosis of gout was further assessed according to the ARA preliminary criteria for the acute arthritis of primary gout [14]. Participants were examined for presence of tophi. These were classified as definite (asymmetric white/yellow swellings on pulling the overlying skin taut) or possible (asymmetric nodular swellings without white/yellow discolouration). Blood was taken for measurement of serum uric acid (SUA) and creatinine. SUA <360 µmol/l was considered to be the target of gout treatment [15, 16].
Statistical analysis
Subjects were excluded from the analysis if more than five (20%) of the WHOQoL questions were unanswered. Subjects were also excluded from the analysis of individual domains if a pre-set number of responses for that domain were missing as follows: physical (1), psychological (1), social (1) and environment (2). Comparison was made between cases and controls for continuous demographic variables using the independent samples t-test and for categorical variables using the chi-squared test.
Overall QOL, satisfaction with health and QOL relating to each of the four domains was compared between gout cases and controls using an independent samples t-test. In the gout patients, this analysis was repeated comparing QOL between cases dichotomized by a cut-off SUA level of 360 µmol/l as described above and by allopurinol use.
QOL, satisfaction with health and domain-specific QOL were then entered in turn as the continuous dependent variable into a stepwise linear regression model with case status (gout = 1 or control = 0), age (years), gender (male = 1 or female = 0), body mass index (BMI) (kg/m2), musculoskeletal co-morbidity (present = 1 or absent = 0) and number of medical co-morbidities as covariates. Musculoskeletal co-morbidity was defined as the presence of any of the following: knee pain, nodal OA (at least two affected rays on each hand) [17], knee/hip replacement or self-reported RA or AS. Analyses were performed using SPSS software version 11.0.
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Results |
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Questionnaires were mailed to a total of 13 684 individuals. Of this, 3082 completed responses were received (23%). Three hundred and fifty-two respondents reported acute attacks of self-limiting synovitis and/or a diagnosis of gout: 199 had been given a diagnosis of gout. Of these 352 subjects, 289 attended the clinical assessment (82%), 137 of whom were thought to have gout (Fig. 1). Subjects attending the clinical assessment who were categorized as definitely not having gout were assigned to the control group. Demographic characteristics of cases and controls are shown in Table 1. Gout cases reported significantly greater history of all co-morbidities apart from renal failure and dialysis. Table 2 shows the disease characteristics of the gout cases.
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Both overall rating of QOL and satisfaction with health were significantly lower in cases than controls (Table 3). On comparison of individual domains, QOL relating to physical health was significantly lower in cases than controls but no significant differences were found for psychological health, social or environment.
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In the multi-variate linear regression model (Table 4), gout was found to be a significant predictor of reduced QOL relating to the physical domain but not overall QOL, satisfaction with health or other domains. Increasing age was a predictor of increased QOL across all domains apart from the physical domain where increasing age predicted reduced QOL. Male gender was only predictive of increased QOL in the psychological domain and reduced QOL in the social domain compared with females. Increasing BMI, medical co-morbidity and musculoskeletal co-morbidity predicted reduced QOL across all domains apart from the social domain where no relationship with BMI was seen. The strongest predictors of overall QOL, satisfaction with health and the physical health-related QOL were medical and musculoskeletal co-morbidity.
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Amongst the gout cases, no difference in QOL was found between cases dichotomized either by SUA level (Table 5) or allopurinol use (Table 6), either overall or in the individual domains.
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Discussion |
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This study shows that in a community sample, gout is associated with impaired overall QOL, satisfaction with health and QOL relating to the physical domain. However, the association between gout and overall QOL and satisfaction with health did not remain significant after adjustment for co-morbid factors. These results suggest that impaired QOL in subjects with gout is largely attributable to associated medical and musculoskeletal co-morbidity rather than to the presence of gout itself. This implies that identification and treatment of medical co-morbidity has implications for QOL in patients with gout. However, the association between gout and impaired QOL in the physical domain remained significant after adjustment for several factors including co-morbidity. Furthermore, gout is frequently under-treated (only 28% were taking urate-lowering therapies in this study) raising the possibility that optimizing the treatment of gout may improve the physical QOL of patients with gout. Although no difference in QOL was found between cases dichotomized according to SUA level or allopurinol use, the numbers of subjects were small and may reflect a type II error.
Only three previous studies have investigated QOL associated with gout. Two hospital-based studies of patients with severe gout (characterized by frequent tophi, erosions and chronic arthropathy) found that QOL was significantly impaired compared with reference values for the general population [8, 9]. One population-based cohort study also identified reduced QOL in gout sufferers compared with control subjects with no musculoskeletal disease [10]. It is noteworthy that in the current study, similar results were seen in a primary care-based cohort with mild disease and infrequent tophi that remained significant after adjustment for co-morbidity.
There are a number of limitations to this study. The main caveat is the low overall response rate raising concerns that the study population may not be representative of the population of the two practices as a whole. The response rate is low for this type of survey: knee pain surveys conducted in similar primary care populations have reported much higher response rates [12]. Another caveat is use of the clinical assessment of a single observer to define the gout cases. The gold standard for the diagnosis of gout remains identification of urate crystals in aspirated synovial fluid. Inter-critical joint aspiration for crystal examination may be an appropriate diagnostic criterion for a retrospective study, however, a requirement to undergo joint aspiration, in addition to venepuncture, may have adversely affected the number of individuals willing to undergo the clinical assessment, so was not included in the protocol. Many studies rely on the 1977 ARA preliminary criteria for the classification of the acute arthritis of primary gout [14]. However, as acknowledged by the authors, these preliminary criteria require further validation and were only intended as criteria for primary gout. Other studies have based the diagnosis of gout solely on general practitioner diagnosis despite misdiagnosis by general practitioners being a concern [18]. The main criterion employed in this study was the clinical diagnosis of a trained observer. This has obvious face-validity and is supported by recent European League Against Rheumatism (EULAR) recommendations for the diagnosis of gout which confirms that a clinical composite of rapid onset pain, tenderness, erythema and swelling affecting the first metatarsophalangeal joint is an excellent clinical marker for gout especially in the presence of hyperuricaemia [19]. This approach risks bias arising from the misclassification of atypical presentations in whom the diagnosis was made following identification of MSU crystals from aspirated synovial fluid or tophus. However, gout is infrequently diagnosed by crystal identification in UK primary care. Of the 289 subjects screened at the clinical assessment, only seven could recall arthrocentesis ever being performed (data not shown).
A wide variety of instruments exist to measure QOL, all of which have their strengths and weaknesses. In this study, QOL was measured using the WHOQoL-Bref [11], a validated 26-item instrument developed from the original 100-item WHOQoL. This instrument has the advantages of recent, international development; however, it measures QOL over the preceding 2 weeks and hence may not be the best instrument for an episodic condition such as gout. Further studies would be aided by the development of a QOL instrument specific for gout to better determine impact of the joint disease per se, to be used in addition to a generic instrument. Importantly, the finding that impaired QOL in the physical domain persisted after adjustment for co-morbidity supports the view that QOL should be included as an outcome measure in clinical trials of interventions for gout.
In summary, gout is associated with poor overall QOL and satisfaction with health, which appears to be secondary to associated co-morbidity rather than gout itself, emphasizing the importance of identifying and treating co-morbidities. However, QOL in the physical domain remains impaired after adjustment for co-morbidities raising the possibility that optimizing the treatment this curable disease may improve physical health-related QOL.
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We would like to thank the staff and patients of Arnold Health Centre and The Calverton Practice in Nottingham, UK. We are grateful for funding from the Arthritis Research Campaign, UK (ICAC grant 14851) and unrestricted financial support from Astra-Zeneca-UK, Glaxo-Smith-Kline-USA and Ipsen, France.
The authors have declared no conflicts of interest.
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