Department of Epidemiology and Public Health, University of Leicester, Leicester,
1 School of Health Policy and Practice, University of East Anglia, Norwich,
2 ARC Epidemiology Unit, University of Manchester, Manchester and
3 Norfolk Arthritis Register, St Michael's Hospital, Aylsham, UK
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Abstract |
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Methods. We conducted a prospective longitudinal study over a 6-month period. The participants were a random sample of 133 individuals who had enrolled with the community-based Norfolk Arthritis Register (NOAR) database between 1994 and 1999. The main outcome measures were the mean (per person) 6-month health service cost, non-health-service cost and total cost associated with IP.
Results. One hundred and fifteen of the 133 individuals who were recruited into the study completed 6 months of follow-up. The mean 6-month total cost was estimated to be £2800 per person, of which 14% was health service costs and the remainder non-health-service costs. Higher total costs were associated with lower health status and rheumatoid factor positivity.
Conclusions. Early IP has a considerable impact on both the health-care system and, more importantly, society. Non-health-service costs (i.e. costs incurred by the individual with the disease, their family and friends) account for a substantial proportion (86%) of the total costs associated with early IP.
KEY WORDS: Inflammatory polyarthritis, Cost of illness, Economics, Health-care costs, Non-health-care costs, Costs.
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Introduction |
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The majority of studies published to date have been US-based and focused on long-term (established) RA in a hospital (clinic) setting [3]. There have been few studies (practical or theoretical) on the costs of RA based in Europe [47] and there is also a lack of studies reporting the costs of early RA, which are increasing in importance since the change in clinical practice to prescribe more aggressive treatment regimes earlier in the disease process [8]. Also, community-based studies are likely to be more representative of the wider disease population.
In 1989 the community-based Norfolk Arthritis Register (NOAR) was set up with the primary aim of identifying and studying all new cases of inflammatory polyarthritis (IP), of which RA is a subset, in the former Norwich Health Authority by notification from general practitioners and hospital clinics [9, 10]. Since the register was established, approximately 250 people each year have agreed to take part in the project. From NOAR data and national population statistics, it can be estimated that there are approximately 22 700 new cases of IP each year in the UK [9].
This paper reports the results of a 6-month longitudinal study designed to estimate the health service, non-health-service and total costs of early IP, using data for a cohort of people from NOAR (i.e. a representative population sample). It provides informative data about how the burden of disease is distributed among not only the health-care system and the individual with the disease, but also other parts of the public sector, such as the individuals family and friends, and society as a whole. This study aimed to assist the decision-making process at policy and planning levels by documenting the extent of resource use in current practice and identifying where the major burden of cost lies in the treatment and care of these people. It also intended to identify the subgroups of people who incur the highest costs. It was not a primary aim of this study to inform choices about which treatment or therapy is the most cost-effective option for people with IP and RA, although we expect that data collected during the study will prove useful for such exercises.
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Methods |
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Study population
The study population consisted of 133 people with early IP (i.e. with disease duration of 5 yr or less) who were enrolled in the community-based NOAR between 1994 and 1999. The study was conducted between June 1999 and May 2000. NOAR inclusion criteria are as follows: (i) age over 16 yr; (ii) swelling of two or more joints; (iii) symptom duration more than 4 weeks; and (iv) symptom onset after January 1990.
Full details of the NOAR study method are published elsewhere [9, 10].
Sources of resource-use data
Resource-use data were collected from participants at three different time pointsbaseline, 3 months and 6 months from the time of recruitment into the studyby the use of self-completion postal questionnaires including the EuroQol [11], which measures health status on a scale from 0=worst imaginable health state to 1=best imaginable health state. The content and structure of the data collection instruments were informed by data extracted from the transcripts of two focus groups conducted on individuals with IP to obtain a better understanding of the types of costs people with IP and their families have to bear as a direct consequence of their illness. Prior to this study, the questionnaires were pilot-tested on two cohorts of individuals from different geographical settings (rural and urban) as a test of external validity, and the response data were validated against an alternative data source, where available, as a test of internal validity.
To minimize recall bias, study participants were provided with a memory aid in the form of a diary in which to record their resource use and expenditure over the 3-month follow-up intervals. Completion of the diary was voluntary, and the diary was for the participants personal use only (i.e. it was not collected from them).
The questionnaires were designed to obtain information regarding the utilization of health-care services and resources, out-of-pocket expenses, time lost from usual activities and household help from family and friends. The NOAR database provided sociodemographic data (age, sex, smoking status, social class and ethnic group) [social class was assigned using the Registrar General's system [41], based on the occupation of the individual] and self-reported functional disability data measured annually using the Health Assessment Questionnaire (HAQ) (scored on a scale from 0=without difficulty to 3=unable to perform) [12].
Sources of unit cost data
Unit costs to supplement the resource-use data were obtained from a number of different sources (Table 1). All costs were expressed in 1998/1999 UK prices.
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Cost analysis
The costing methods used are presented in Table 2. The total 6-month cost per person was estimated by combining resource-use data with unit costs using the following general costing formula:
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Statistical analysis
The main descriptive statistics presented are the arithmetic mean, standard deviation (S.D.), median and interquartile range (IQR) [13]. Exploratory data analysis was used to study the distribution of costs. The study population was categorized into three age groups (1639, 4059 and 60 yr and over) and their HAQ and EuroQol scores were categorized into tertiles.
A multiple linear regression model was fitted to the log-transformed cost data and parameters were estimated using forward stepwise regression to identify which sociodemographic and clinical characteristics influenced cost.
Sensitivity analysis
The sensitivity of the costs estimated in the main analysis to changes in the following variables were investigated.
Health service costs
In-patient care costs were varied by ±40% and out-patient care costs by ±15% to make allowances for variation in provider costs across the UK, as illustrated in the NHS reference costs [14].
Non-health service costs
The cost per mile travelled was varied from 45 to 185 pence [15], the cost per hour of paid help was increased from 770 pence (weekday rate) to 1200 pence (weekend rate) [16], and the cost of non-working/leisure time was varied from 24.7% of working time cost for the main analysis [17, 18] to 40% (600 pence per hour) [17].
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Results |
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Statistical analysis
To determine which sociodemographic and clinical characteristics influenced cost, a multiple linear regression model was fitted to the log-transformed cost data. Note that the cost data were transformed to obtain a more symmetrical distribution (Fig. 5). The sociodemographic and clinical variables considered for inclusion in the model are listed in Table 5
. Note that, for the purposes of this analysis, the EuroQol and HAQ scores were categorized into tertiles. It can be observed from Table 5
that the mean cost appeared to increase with HAQ score and decrease with EuroQol score, as would be expected. There also appeared to be a difference between the mean costs for individuals who were positive and negative for rheumatoid factor. Note that the EuroQol score was not included in the regression model as it was found to be highly correlated with the HAQ score (rS=-0.414, P<0.005). The final model included three of the seven variables, all of which were simultaneously significantly associated with cost (P<0.05): rheumatoid factor, HAQ score (level 1 and 2) and age (Table 6
). The adjusted r2 value for this model was 29%, indicating that the variability in cost is only partly explained by the predictor variables in the model.
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Sensitivity analysis
The uncertain parameters in the analysis of health service costs were the secondary care costs, which were based on generic unit costs for out-patient visits and in-patient stays. Such costs vary greatly from hospital to hospital across the UK and therefore the health service costs were reworked. The lower extreme for the mean 6-month cost (i.e. reducing out-patient costs by 15% and in-patient and day-unit costs by 40%) was £330 and the upper extreme (i.e. increasing out-patient costs by 15% and in-patient and day-unit costs by 40%) was £449. This was a change in health service costs of ±15%. Similarly, the uncertain parameters in the analysis of non-health-service costs were unit cost of household help, cost per mile and cost per hour of non-working/leisure time. The mean 6-month cost for the main analysis was £2406. When all of the above parameters were varied within the ranges defined in the Methods section, the lower extreme was £2176 and the upper extreme £3582.
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Discussion |
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As with the effects of disease course and treatment, costs also show vast variability between individuals with IP. Whilst the aggregated results of such a heterogeneous group are of limited value for decision-making, the mean cost (for the average individual) may be used to inform budget-setting for a new cohort of individuals. As can be observed from Fig. 1, a relatively small number of individuals incur high costs, which skews the distribution of cost data to the right and inflates the mean value above the median value. Although total costs cannot be derived from it, the median value does provide useful information on the most typical cost for an individual subject. Due to random variation, the number of high-cost individuals may vary considerably between years and rheumatology departments. Clearly, such variability may have substantive effects on tight budgets. In this cohort, 10% of the individuals incurred 50% of the total 6-month costs.
The main component of health-service costs was in-patient stays and day care followed by prescribed medication, which accounted for 33 and 30% of total health-service costs respectively. The minority of study individuals who incurred an in-patient stay or day-care visit (6%) accounted for a large proportion of the total 6-month health-service costs (42%). These findings were similar to those for asthma [22, 23] and multiple sclerosis [24].
Overall, average (per person) health service costs were considerably lower than previous study findings. Reasons for this include differences in (i) the population under surveillance (e.g. early IP vs established disease); (ii) the classification of the disease (IP vs RA); (iii) the availability of a day-care unit; (iv) the base year of the study (i.e. change in clinical practice over time); (v) the availability of routine cost data for health-care; and (vi) study setting (community vs clinic).
Only the studies by van Jaarsveld et al. [6] from The Netherlands and Newhall-Perry et al. [25] from the USA were concerned with the costs of early disease. The former study investigated the costs of RA over the first 6 yr after onset whereas the latter study concentrated on the first year after onset. In both studies the participants were, on average, more functionally disabled (mean HAQ 1.25) than in the present study (mean HAQ 0.89). The health-care costs that were estimated by van Jaarsveld et al. [6] greatly exceeded those reported in the present paper, which reflects the clinic setting of the study of van Jaarsveld et al. and the case mix of the population of interest. However, the study of Newhall-Perry et al. [25] was community-based, like this study, and therefore provided similar cost estimates.
It is important to remind the reader that this was an evaluation of early IP and therefore costs to the health service are likely to increase still further as the disease becomes more progressive (e.g. surgery costs, especially total knee or total hip arthroplasty, combined with postoperative infections and other surgical complications) [26, 27].
The costs incurred by individuals as a result of their IP were found to be substantial [46% of total 6-month cost per person, equivalent to 17% of average income (£1300 per person)]. In this study, only a small percentage of all household help was paid for (between 0.9 and 3.7%), which agrees with the findings of Medeiros et al. [28]. The cost of informal (unpaid) care is likely to vary depending on household and social capital available; for example, structures of society that provide help (e.g. self-help groups) and public resources, which may increase the potential of society (e.g. social services). Medeiros et al. [28] reported that low socio-economic level and lack of social support resulted in reduced quality of life of caregivers. Therefore, it is important for future research to investigate and, if necessary, refine social support provisions to ensure greater quality of life for caregivers.
Costs incurred by friends and family as a result of an individual's IP are often omitted from studies investigating the economic impact of IP/RA. This is a sizeable omission as friends and family costs accounted for a substantial proportion (35%) of total 6-month cost per person (£983, 95% CI £6781338). The majority of this cost was attributable to informal care around the home (30% of total cost), a result also found in multiple sclerosis research (26% of total cost) [24]. In later, more established disease, one of the major components of cost is reported to be long-term care in residential or nursing home accommodation, which is linked to deterioration in functional disability and quality of life [29].
In this study, time lost from work as a consequence of an individual's IP, which was covered by a statutory sick-pay scheme, was considered to be a cost to the employer and government. However, in some cases, especially short-time sickness absence, the employer may not incur the cost if it is possible for the work to be made up on an individual's return to work or absorbed by other workers at no extra cost.
Other agents who incurred costs as a result of an individual's IP were social services and/or voluntary organizations, in the form of household help and providers of aids and home adaptations. Although such costs were minimal (0.03% of total 6-month cost per person) in this economic study of early IP, it is reasonable to assume that the role of social services and voluntary organizations will increase as an individual's IP progresses over time, especially for individuals without informal social support. Therefore, there is a need for future studies of more established IP to measure the extent of these costs to assist the planning of services for individuals without informal social support.
Overall, there was no statistically significant association between total 6-month cost and the number of years registered with NOAR. Individuals with high health-service costs also tended to encounter higher non-health-service costs. The results from the multiple linear regression model showed cost to have a positive association with rheumatoid factor and HAQ score and a negative association with age. These results agreed with the findings of van Jaarsveld et al. [6].
The change in the treatment regime, together with the development of a new generation of therapies [for example, cyclo-oxygenase-2 (COX-2) inhibitors [30, 31] and tumour necrosis factor drugs] will have major effects on the cost of treating RA. Therefore, it is important that the efficacy and cost-effectiveness of these new therapies are investigated from the perspective both of the health provider and of society. It is important that future cost-effectiveness analyses are based on good-quality primary research on costs and cost behaviour of the type presented above. Such detailed cost data can then be used to inform the cost side of decision analysis models designed to assess the cost-effectiveness of new treatment regimes at an early stage, in order to assess the desirability of further research. In addition to the above, new expensive therapies also require considerable clinical judgement to enable them to be used effectively [32].
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Acknowledgments |
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Notes |
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References |
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