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Rheumatology Advance Access originally published online on May 25, 2006
Rheumatology 2007 46(1):105-111; doi:10.1093/rheumatology/kel155
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© The Author 2006. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org

Direct healthcare costs and predictors of costs in patients with primary Sjögren's syndrome

R. Callaghan, A. Prabu, R. B. Allan, A. E. Clarke1, N. Sutcliffe2, Yvan St. Pierre1, C. Gordon, S. J. Bowman and the UK Sjögren's Interest Group*

Rheumatology Department, Division of Immunity and Infection, The University of Birmingham, UK, 1Department of Medicine, McGill University, Montreal, Quebec, Canada and 2Centre for Rheumatology, Department of Medicine, University College London, London, UK.

Correspondence to: Dr Rob Callaghan, Department of Rheumatology, Nevill Hall Hospital, Brecon Road, Abergavenny NP7 7EG, UK. E-mail: robcallaghan{at}doctors.org.uk


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 Acknowledgements
 References
 
Objectives. To analyse the healthcare usage, direct healthcare costs and predictors of cost in primary Sjögren's syndrome (PSS) in the UK and to compare the findings with the data from healthy control groups and rheumatoid arthritis (RA) patients.

Methods. A total of 129 patients with PSS (American–European criteria), 91 with RA and 92 controls, were included in the study. All groups were age-matched females and all completed questionnaires on health status (SF-36) and healthcare utilization (economic component of the Stanford Health Assessment Questionnaire). Annual direct healthcare costs were calculated (and expressed in 2004 UK pound sterling) and predictors of costs for each patient group were determined by regression analyses. Age, health status, disease duration and anti-Ro/La antibody positivity were used as potential predictor variables.

Results. Mean age was similar in the PSS (59.2 yrs, S.D. 11.6), RA (60.3 yrs, S.D. 10.5) and control groups (57.7 yrs, S.D. 12.5). The mean disease duration was 5.4 yrs (S.D. 4.8) in the PSS group and 13.4 yrs (S.D. 11.4) in the RA group. The mean annual total direct cost per patient [95% confidence interval (CI)] was £2188 (£1831 and £2546) in the PSS group, £2693 (£2069 and £3428) in the RA group and £949 (£741 and £1156) in the control group. The costs in the PSS group were greater than for the RA and control groups for visits to all healthcare professionals (total) as well as visits to the dentist, dental hospital and ophthalmologist. The costs in the PSS and RA groups were higher than in controls for diagnostic tests and visits to hospital and the accident and emergency (A&E) department. The PSS group also incurred higher costs than controls, but lower costs than the RA group, for visits to a rheumatologist, urine and blood tests, assistive devices and drug therapy. Regression analysis identified the SF-36 physical function subscale as the best predictor of costs in PSS patients as well as controls and the mental health subscale in RA patients.

Conclusion. This is the first study to evaluate direct healthcare costs in patients with PSS. PSS has a significant impact on the healthcare system, similar to that of RA, by more than doubling costs compared with control patients.

KEY WORDS: Primary Sjögren's syndrome, Healthcare usage, Comorbidity, Costs, Predictors of cost


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 Acknowledgements
 References
 
Primary Sjögren's syndrome (PSS) is a multisystem immune-mediated disease characterized by chronic inflammation of the exocrine (especially salivary and lacrimal) glands [1], leading to clinical symptoms of dry eyes and mouth. PSS typically affects women during the fourth and fifth decades of life, with a female:male ratio of 9:1. Sjögren's syndrome can also occur in association with other autoimmune diseases such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) or scleroderma (secondary Sjögren's syndrome). The spectrum of PSS extends from an organ-specific disorder (autoimmune exocrinopathy) to a systemic process that may also involve the musculoskeletal, pulmonary, gastrointestinal, hepatobiliary, haematological, vascular, dermatological, renal or nervous systems [1].

Substantially reduced health-related quality of life has been demonstrated in patients with PSS, using the 36-item form of the Medical Outcome Survey (SF-36) questionnaire [2–5]. In the current political climate, physicians are now becoming more aware of healthcare budgets and costs. We would predict that the reduced health-related quality of life would translate into greater healthcare costs for PSS patients than for healthy controls. This is important in understanding the implications of the condition for the health service and to improve allocation of resources.

There have been a number of studies evaluating the costs of rheumatic diseases such as RA [6–11] and SLE [12–15], but to our knowledge none has looked specifically at the direct financial consequences to the health service of PSS.

Cost identification analysis is an important first step in performing any economic evaluation. Direct healthcare costs, one component of total medical costs, refer to the resources consumed in delivering care to the patient and include costs for in-patient, out-patient and emergency care.

In this study, we analysed the healthcare usage, the direct healthcare costs and the predictors of cost in PSS in the UK and compared the findings with the data from RA and healthy control groups.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 Acknowledgements
 References
 
Patients
Multi-centre Research Ethics Committee approval was obtained, and written informed consent was given by the participants. Since PSS is predominantly a condition affecting females and because of the very small number of non-Caucasians in our cohort, it was decided to limit the study to female Caucasian patients. In a preliminary evaluation of our PSS cohort [16], almost all the patients were between 35 and 74 yrs and this age range was therefore used in the recruitment of the control groups.

We have previously reported data on fatigue and discomfort and sicca symptoms in these groups of patients and controls [5, 17]. For this study, 135 consecutive female Caucasian patients with PSS fulfilling the American European Consensus Criteria [18] were recruited from hospital rheumatology out-patient departments at 12 participating centres in the UK. One hundred and four consecutive female Caucasian RA patients fulfilling the 1987 revised American Rheumatism Association (ARA) criteria for the classification of RA [19] were recruited from a general rheumatology clinic in Birmingham, UK.

The community control group consisted of 103 Caucasian women without inflammatory rheumatic conditions. They were recruited by postal invitation from two general practitioners’ (GPs) lists from the Birmingham area as previously described [16]. For this study consecutive responders to the postal invitation who did not have oral or ocular dryness symptoms were invited to attend an interview.

Data collection for all groups occurred in 2001. A small number of recruits were found to be outside the originally specified age range, but it was decided not to exclude them from the study; three PSS patients and two RA patients were under 35 yrs; seven PSS patients, five RA patients and three controls were over 75 yrs.

Measures
The SF-36 is a widely used 36-item health questionnaire that measures eight multi-item dimensions: physical function, role limitations due to physical problems, role limitations due to emotional problems, social function, mental health, general health perception, vitality and pain. Thirty-five of the items contribute to these scales. There is a further unscaled single item asking respondents about health change over the past year. For each dimension, item scores are coded, summed and transformed onto a scale from 0 (worst possible health state) to 100 (best possible health state) [20]. Physical (PCS) and mental component summary (MCS) scores, generated by collapsing the eight subscales, were also calculated [21].

Patients also completed a modified version of the economic portion of the Stanford Health Assessment Questionnaire [22] as previously used [8, 9] and validated [12, 23] in other rheumatic disorders. The questionnaire asks about the utilization of healthcare resources over the past 6 months including out-patient and other hospital visits, prescribed and non-prescribed medications and therapies, investigations and assistive devices and patients’ employment status. Patients are requested to report on all healthcare utilization without making attribution to a specific disease.

Anti-Ro/La antibody status was measured in all patients’ serum by the Immunology Department at University Hospital Birmingham using a standard validated commercial assay. For the PSS and RA groups, previous labial gland biopsy results and comorbidity data were also collected through review of medical notes. Disease activity was assessed in the RA group using the 28 joint disease activity score (DAS28) [24].

Assessment of costs
Healthcare utilization data was collected over a 6-month period. Cost calculations were performed and expressed as annual costs in 2004–5 UK pound sterling.

The cost of hospital stays and the majority of costs for visits to healthcare professionals (excluding visits to a GP, optician, district nurse and dentist) were calculated from the 2004–5 Department of Health's (DoH's) new tariff price list. These are government derived standard national UK prices, which form the basis of the contracts between Primary Care Trusts and UK hospitals. For out-patient visits follow-up tariff costs, rather than first attendance tariffs, were used. The tariff for hospital stays are ‘spell’ based tariffs (current UK terminology) that calculate an average cost for a specific in-patient episode and include all costs involved in the patients in-patient stay (regardless of length of stay). All of the DoH tariff costs are adjusted across the UK for specific market forces, and in our region (Birmingham Solihull & Heartlands NHS Trust) a factor of 0.9785 was applied to all these costs. Some A&E attendances were via ambulance, and an additional cost to cover ambulance transfer was added to each of these visits. This was an average cost obtained directly from the West Midlands Ambulance Service NHS Trust (personal communication).

Apart from the national ‘spell’ tariffs, other costs, including those for diagnostic investigations, visits to a GP, optician, district nurse, physiotherapist and dentist, were calculated via direct communication with the business managers of the appropriate departments in either Birmingham Solihull & Heartlands Hospital NHS Trust or Birmingham & Solihull Primary Care Trust. In all cases, an additional estimated cost was added to their standard price list to cover overhead costs (e.g. the cost of staff and other resources used in order to provide the service including the cost of technicians and reporting physicians where applicable). This was done throughout the costs analysis process in order to produce the most accurate costs possible. The cost of visits to a social worker were obtained from Solihull Metropolitan Borough Council.

Prescription and non-prescription medication prices were calculated as the product of the price per milligram, total daily dose and therapy duration. The price per milligram for each medication was based on the local drug tariff (2004).

For the purpose of this study, the assumption was made that most of the study patients have their medications supplied by the community pharmacists every 3 months (the community pharmacists are reimbursed according to the local drug tariff). An additional community pharmacy professional fee was added for each 3-monthly prescription.

The costs of assistive devices were obtained from the surgical appliance department at Solihull Hospital, Birmingham (personal communication). For costing purposes, it was assumed that an assistive device is used for an average of 3 yrs before being replaced.

Statistical analysis
Data on demographics and disease characteristics were compared between groups using means and standard deviations. Mean values for specific items of healthcare costs for PSS patients were compared with those of controls and of RA patients by constructing a 95% CI around the differences in order to assess their statistical significance. Similar comparisons were done for proportions of patients using certain medications or alternative therapies, as well as presenting comorbidities, and employment characteristics of interest.

Three separate regression analyses were performed for each group to assess potential predictors of direct total costs. In regression models for cost data, it is desirable to analyse untransformed costs so that the models predict actual costs in pounds. Because of the skewed nature of cost data, it is recommended [25] that non-parametric bootstrap methods [26] be used to calculate CIs for regression coefficients. Since no automated bootstrap methods are available to select important variables for inclusion in regression models, standard parametric analyses were used to measure the association of cost with a number of potential predictors, and CIs for each of these univariate relationships were calculated using bootstrap methods. However, variable selection for models with best predictive power was done by an algorithm fitting models with all plausible combinations of potential predictors, and then choosing among these the model that minimized the Bayes Information Criterion [27]. Bootstrap CIs were constructed for all models from 1000 replicate samples, using STATA version 6 software. The variable selection for best predictive models was carried out using S-Plus. All other analyses were carried out in SAS.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 Acknowledgements
 References
 
Patient characteristics
Out of 135 PSS patients 129 (96%), 91 of 104 RA patients (88%) and 92 out of 103 (89%) controls who were invited to do so participated in the study.

The mean age was similar in the PSS (59.2 yrs, S.D. 11.6), RA (60.3 yrs, S.D. 10.5) and control (57.7 yrs, S.D. 12.5) groups. The mean disease duration was 5.4 yrs (S.D. 4.8) in the PSS group and 13.4 yrs (S.D. 11.4) in the RA group. Since symptom onset in PSS often predates the formal diagnosis by several years, this may not be biologically significant and will not be addressed further.

Of the 129 patients with PSS, 105 (81%) were positive for anti-Ro and/or anti-La antibodies compared with 3/91 (3%) of the RA patients and 2/92 (2%) of the controls tested. Of 73 PSS patients who had undergone a labial gland biopsy, 70 had a result consistent with the diagnosis of Sjögren's syndrome, while in the remaining three the biopsy sample was non-diagnostic. Twenty-one RA patients had sicca symptoms with objective evidence of either oral or ocular dryness but not both, while two RA patients with sicca symptoms had objective evidence of both oral and ocular dryness, thereby fulfilling the criteria for secondary Sjögren's syndrome. None of the RA patients or controls had undergone a labial gland biopsy. The mean DAS28 for the RA group was 4.3 (S.D. 1.3).

Visits to healthcare professionals
Table 1 shows the overall annual costs for each of the three patient groups along with the mean differences and 95% CI between PSS and controls, and PSS and RA patients.


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  		TABLE 1. Annual costs in 2004 UK pound sterling

 
Costs of visits to a healthcare professional were highest in the PSS group (£1182) compared with controls (£603) and the RA group (£849). Regarding individual healthcare providers, the PSS group (compared with the control and RA groups), had the highest costs for visits to the dentist or dental hospital (£452) and ophthalmologist (£66). Costs in the PSS group (compared with controls only) were also higher for visits to a GP (£322), rheumatologist (£166), ENT surgeon (£18) and other healthcare professionals (£114). The cost for visits to a rheumatologist was highest in the RA group (£260).

Hospital stay
Hospital stay costs included A&E, day care and in-patient costs. The PSS group had higher hospital stay costs (£491) compared with controls (£144). There was no significant difference between costs in the PSS and RA group (£881).

Diagnostic tests
Overall costs for diagnostic tests were higher in the PSS group (£365) compared with controls (£162). The PSS group also had higher costs for blood or urine tests (£158) and X-rays (£81) (not including mammograms) compared with controls (£38 and £28, respectively). Blood or urine test costs were higher in the RA group (£268) compared with the PSS group. There was no difference in costs between PSS and controls and PSS and RA groups for other diagnostic tests.

Drug therapy
Overall costs for drug therapy were higher in the PSS group (£97) compared with controls (£27), but less in the PSS group compared with RA patients (£184).

Table 2 shows the percentage of patients receiving medication over the previous 6 months along with the mean percentage differences between PSS and controls, and PSS and RA patients.


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  		TABLE 2. Use of medications and alternative therapies and presence of comorbidities

 
PSS patients were more likely to be taking NSAIDs (54%), corticosteroids (12%), DMARDs (32%), painkillers (57%), antidepressants (14%), gastroprotective agents (22%), bone protection (14%) and artificial tears or saliva (78%) compared with controls (30, 2, 1, 37, 2, 2, 3 and 0%, respectively).

PSS patients were using more artificial tears or saliva compared with RA patients (5%), but were using fewer non-steroidal anti-inflammatory drugs (NSAIDs), corticosteroids, disease-modifying anti-rheumatic drugs (DMARDs) and painkillers compared with RA patients (69, 45, 89 and 79%, respectively).

Assistive devices
Overall cost for assistive devices was higher in the RA group (£319) compared with PSS group (£54) (Table 1). Both the groups had higher costs compared with controls (£13).

Alternative therapy use and comorbidities
Table 2 shows the percentage of patients using alternative therapies over the previous 6 months along with the mean percentage differences between PSS and controls, and PSS and RA patients. It also shows comorbidity data for each group.

Overall use of alternative therapies was higher in PSS patients (50%) compared with RA patients (18%). Use of relaxation therapy (20%), imagery (5%), herbal medicine (19%), massage (14%) and megavitamin therapy (10%) was more frequent in the PSS than in the RA group. The use of self-help groups was more common in PSS patients (9%) compared with controls (0%).

Compared with controls, PSS patients had a higher frequency of psoriasis (22 vs 3%), hypothyroidism (12 vs 4%) and osteoporosis (3 vs 0%) and a lower frequency of hayfever (2 vs 11%). Compared with RA patients, PSS patients had a higher frequency of osteoarthritis (16 vs 7%) and psoriasis (22 vs 1%) and a lower frequency of hypertension (8 vs 19%).

Employment data
Although this article does not address indirect healthcare costs, preliminary data on employment status was recorded. Eighty-seven per cent of the PSS patients, 69% of the RA patients and 83% of the controls completed details about employment characteristics (Table 3). More PSS patients (30%) were in full- or part-time employment than RA patients (11%). Although not statistically different, 6% of PSS patients, 3% of RA patients and 5% of controls were unemployed, and the respective figures for retirement in the three groups were 52, 57 and 43%. More RA patients (22%) were registered disabled than PSS patients (5%).


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  		TABLE 3. Employment characteristics of patients and controls

 
Predictors of costs
SF-36 data were collected on 126 of 129 PSS patients, 89 of 91 RA patients and 85 of 92 controls. The results of regression analyses for annual costs in the three groups are shown in Table 4. The table shows regression coefficients (bootstrap 95% CIs) for each of the potential predictors of cost, which represent the additional annual costs associated with one-unit changes in each of these factors. In the PSS group, these univariate parametric analyses of costs suggested longer disease duration and poorer scores on the physical function subscale of the SF-36, and the physical component summary of the SF-36 were associated with higher costs. In the RA group, poorer scores on the physical function, role physical, body pain, vitality, social function, role emotional and mental health subscales of the SF-36 and the MCS of the SF-36 were associated with higher costs. In the control group, poorer scores on the physical function, role physical, body pain, general health, vitality, social function and role emotional subscales of the SF-36 and the PCS of the SF-36 were associated with higher costs.


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  		TABLE 4. Predictors of costs

 
For best model selection, the Bayesian information criterion identified a model including only the SF-36 physical function subscale as the best predictive model of costs in PSS patients as well as controls, and another including only the mental health subscale in RA patients.


   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
Acknowledgements
 References
 
A number of studies have consistently shown that PSS patients have reduced health-related quality of life [2–5]. Since the healthcare usage of any population is likely to be related to the health status of its members [28], we would predict that patients with PSS would make greater use of healthcare services than healthy controls and that this would translate into greater direct healthcare costs. As far as we are aware, ours is the first study to examine this.

This study showed similar total mean direct healthcare costs in the PSS and RA groups (£2188 and £2693), which were significantly greater than those of controls (£949). The PSS group incurred the highest costs for healthcare professionals, largely because of their visits to the dentist or dental hospital and the ophthalmologist. This is clearly related to the oral and ocular dryness that PSS patients experience and the resultant necessity for regular specialist checkups. The biggest component of the total costs in the RA group was for a hospital stay (£881). This is not surprising as RA patients have more chronic disability than PSS patients and therefore require more in-patient care. Clarke et al. [8] also reported that hospital care costs were the highest costs in their RA cohort. The RA group also had the highest costs for drug therapy and assistive devices although the RA drug therapy costs were fairly modest, and this may reflect the fact that data collection was carried out before the widespread use of biological therapy in the UK. Assuming that 6% of RA patients are now receiving biological therapy [29] at a cost of circa £10 000 per patient, this adds an average of approximately £600 to the mean total direct costs per RA patient (i.e. a total of approximately £3293).

Previous studies of RA and SLE have also shown reduced health-related quality of life and increased use of healthcare resources and increased direct healthcare costs [8–12, 15, 30–34]. Our data on RA were compatible with the results of these studies and showed that the usage of healthcare resources by PSS patients was intermediate between RA patients and controls. Girard et al. [30] and Gabriel et al. [33] specifically compared healthcare utilization in RA patients with non-arthritic subjects and found similar increases in healthcare resource utilization in the RA group.

Along with the direct healthcare costs of disease, there is also substantial work disability or unemployment (indirect healthcare costs). In previous studies using similar methodology in SLE in the UK [9] and Canada [34] and in RA in Canada [8], these have varied from half to double the direct costs. Although we have not formally evaluated indirect costs in the current study, we would speculate, from the preliminary employment data, that indirect costs may also prove to be higher in the PSS group compared with controls, and lower than those for RA patients, although this needs to be formally evaluated in future studies.

PSS patients also made more use of alternative therapies than RA patients. The use of various forms of alternative therapies in PSS patients is well-documented in the literature [35], although we are not aware of any papers specifically comparing their use in PSS patients with RA patients and controls. There are several reports of the use of acupuncture [40, 36–39], particularly for the treatment of xerostomia, and also the use of herbal remedies in PSS patients [40, 41]. In our study, there was less use of relaxation, imagery, herbal medicine, massage and megavitamins by RA patients than by PSS patients. In contrast, there are many studies reporting high usage of alternative therapies in RA patients [42, 43], although often such studies are biased by low response rates.

In terms of what factors best predicted direct healthcare costs, PSS patients with better physical functioning incurred lower direct costs, whereas in the RA group the mental health subscale of the SF-36 was the best predictor of costs. It is interesting that physical functioning was not the best predictor of costs in the RA group. Perhaps this reflects the significant psychological impact that RA has on its patients. The association of physical functioning with direct costs in SLE patients was also shown in the studies by Clarke et al. [12, 13]. The patients with better physical functioning may also lose less time from work. Being Ro/La-positive or having biopsy-positive PSS was not associated with higher direct costs.

Although the study populations were age-matched, we do appreciate that all were Caucasian females, and therefore the data may not be generalizable to non-Caucasians or men with PSS. This study also examined a cohort of UK hospital patients under the care of rheumatologists with a particular interest in PSS and may therefore overestimate the resources used by this cohort in comparison with Sjögren's patients seen in other less-specialized clinics. Although our control group excluded patients known to have an inflammatory disorder, we did not exclude common comorbidities such as osteoarthritis, which is likely due to the high use of NSAIDs and painkillers in this group. This was in order to try and create a ‘real-life’ comparison that reflected the age range used in this study. One control was on a DMARD for inflammatory bowel disease that was currently in remission.

In summary, we have shown that PSS patients make substantial use of healthcare services, specifically with regard to total healthcare visits. Costs in the PSS group for hospital stays, diagnostic tests, drug therapy and assistive devices were also greater than for controls although not as great as patients with RA (or compared with previously reported data for SLE). Direct healthcare costs in the PSS group were more than double those in the control group and of a similar amount to those of the RA group studied prior to the introduction of biological therapies. With changes in the NHS and other healthcare systems, there is increasing need to examine the costs of service delivery and to justify the introduction of new therapies based on cost savings as well as efficacy. As biological therapies are increasingly used for the treatment of rheumatic diseases, these data provide a baseline for consideration of health economic analyses for any future trials of such therapies in Sjögren's syndrome. It also demonstrates that the reduced health status in PSS is reflected in the increased direct health costs, and this underscores the need to treat the condition more aggressively than may be perceived by many healthcare professionals at present.


   Acknowledgements
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Acknowledgements
References
 
This research was funded by project grants from the Arthritis Research Campaign, the British Sjögren's Syndrome Association (BSSA) and the University Hospital Birmingham Trust (Primary Care Award) with Professor R. Hobbs and Ros Salter. Logistical support was received through the Arthritis Research Campaign Integrated Clinical Arthritis Centre Award to the Rheumatology Department. We thank Dr A. Khan and Dr S. Debenham and colleagues for allowing access to their patients in the community and to our hospital colleagues Prof. P. Bacon, Prof. S. Challacombe, Dr A. Faizal, Dr P. Jobanputra, Dr R. Jubb, Dr R. Palmer, Dr M. Pugh and Dr E. Rankin for access to their patients. Supported by the Arthritis Research Campaign (UK), University Hospitals Birmingham NHS Trust (in collaboration with Professor R Hobbs and Ros Salter) and the British Sjögren's Syndrome Association.

The authors have declared no conflicts of interest.


   Notes
 
* The UK Sjögren's Interest Group includes: Deva Situnayake MD, FRCP, Liviu Hanu-Cernat MBBS, FDSRCS, Stephanie Heaton RGN and Bernard Speculand FDS, FRACDS, City Hospital, Birmingham; John Ainsworth FRCOphth, Ahmed Bawendi MSc, MD and Georgina Holmes RGN, Birmingham Heartlands and Solihull Hospitals, Birmingham; John Hamburger FDS, FRCPath, School of Dentistry, Birmingham; David A. Booth PhD, DSc, CPsychol, FBPsS and Rosemary G. Platts BA, School of Psychology, The University of Birmingham; Peter Maddison MD, FRCP, Bangor, Wales; Diarmuid Mulherin MD, MRCP, Cannock Chase Hospital, Staffordshire; Pepe Shirlaw BDS, FDSRCPS, UMDS, London; Michael Snaith MD, FRCP, Mohammed Akil MD, FRCP and Christine Yeoman PhD, FDSRCS, Royal Hallamshire Hospital, Sheffield; Anne Field DDSci, FDSRCS, Jocelyn Rostron BDS, FDSRCS, Luke Dawson PhD, and Leslie Longman PhD, FDSRCS, Liverpool Dental Hospital, Liverpool; Ian Griffiths BSc, FRCP and Brian Davidson MD, MRCP, Freeman Hospital, Newcastle; Neil McHugh MD, FRCP and Ms Nicola Waldron RGN, Royal National Hospital, Bath; Colin Pease MD, FRCP and Elizabeth Tyas RGN, Leeds General Infirmary, Leeds; Elizabeth Price MD, FRCP, Princess Margaret Hospital, Swindon; David Isenberg MD, FRCP, Maria-Jose Leandro MD and Nurhan Sutcliffe MD, MRCP, Middlesex Hospital London, UK. Back


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Acknowledgements
 References
 

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Submitted 13 December 2005; revised version accepted 7 April 2006.
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