|Costs and outcomes of total hip and knee joint replacement for rheumatoid arthritis
|March L M, Barcenilla A L, Cross M J, Lapsley H M, Parker D, Brooks P M
This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn.
This study examined the clinical and economic impact of primary unilateral total knee replacement (TKR) and total hip replacement (THR) in patients with rheumatoid arthritis. The authors concluded that surgery reduced the post-operative costs from the perspective of the patient and the health care system, and improved the health outcomes for both THR and TKR patients. Although well described, the study had some methodological limitations, relating to its design, and the conclusions should be treated with caution.
Type of economic evaluation
The objective was to examine the clinical and economic impact of primary unilateral total knee replacement (TKR) and total hip replacement (THR) in patients with rheumatoid arthritis.
The health technologies examined were TKR and THR. Each surgical procedure was compared with no intervention.
Australia/hospital and community (home).
This economic evaluation was based on a single study with a time horizon of 15 months. The authors stated that the perspective of the patient was adopted.
The clinical data came from a prospective cohort study with historical control carried out in five hospitals in the city of Sidney, Australia. The data were collected retrospectively for the three months before surgery, and prospectively for the 12 months after surgery. A total of 70 patients were eligible to participate, but only 42 were included. There were 31 patients in the TKR group (average age: 60 years, 77% female) and 11 patients in the THR group (average age: 57 years, 91% female). The key clinical endpoints were the patients’ health conditions measured using the Short Form (SF)-36, the Health Assessment Questionnaire (HAQ), and the visual analogue scale (VAS). These data were obtained three months pre-operatively, and three months and 12 months post-operatively.
Monetary benefit and utility valuations:
Measure of benefit:
No summary benefit measure was used and the three clinical outcomes were SF-36, HAQ, and VAS scores.
The economic analysis included patients’ out-of-pocket expenses for: medications (both prescription and non-prescription), visits to health care professionals, diagnostic tests, special equipment, household alterations, and the use of private or community services. The utilisation of health care system resources was also analysed and this included visits to medical practitioners, tests, and visits to public hospital out-patient clinics where patients had no out-of-pocket expenses. The out-of-pocket costs for the acute hospital stay and surgeons fees associated with joint replacement surgery were not included. The resource use data and costs were based on cost diaries, which were completed at baseline for the previous three months (pre-operative phase) and every three months for the post-operative year. All costs were in Australian dollars (AUD) for the year 2005.
Analysis of uncertainty:
Not carried out.
For TKR patients, significant improvements in the SF-36 scores (on physical function, role physical, mental health, and the physical component scales) were observed from three months pre-operatively to three months post-operatively. At one year, the dimensions of physical function, bodily pain, social function, role emotional, and the mental component were significantly improved over the pre-operative scores. A similar improvement was observed in the HAQ at three months post-operatively (1.37) compared with pre-operatively (1.63), but at 12 months the difference was not statistically significant. The VAS showed a significant reduction in the severity of pain from pre-operatively (56mm) to 12 months post-operatively (39mm).
For THR patients, similar findings were observed, with respect to the SF-36, but there were no statistically significant differences in the HAQ scores (1.56 pre-operatively compared with 1.39 three months and 1.5 one year post-operatively). The VAS score improved significantly from pre-operatively (61mm) to 12 months post-operatively (33mm).
Out-of-pocket expenses and health care service utilisation decreased over the post-operative year for both groups of patients. For TKR patients, the mean out-of-pocket expenses decreased significantly for the first three months after surgery (AUD 388) compared with before surgery (AUD 911). This significant cost reduction was sustained over the whole post-operative year. For THR patients, the mean expenses decreased by AUD 572 from the pre-operative period to the 9- to 12-month post-operative period, but this decrease did not reach statistical significance.
The analysis of cost components revealed that, for both groups, the greatest component was special equipment before surgery, and private service at one year after surgery.
The authors concluded that surgery for rheumatoid arthritis patients reduced the post-operative costs from the perspective of the patient and the health care system, and at the same time, improved the health outcomes for both THR and TKR patients. They suggested that, for accuracy, the assessment of health status should be based on the Western Ontario and McMaster Universities (WOMAC) measure.
The rationale for the selection of the comparators for each group of patients was clear in that the pre-operative period was compared with the post-operative period.
A ‘before-after-study’ study is based on a single cohort of patients, without an external control group, and each patient acts as their own control. This design has the advantage of not requiring statistical methods to ensure the comparability of the intervention and control groups, but its main limitation is that the two strategies (no intervention and the surgical procedure) are compared in two different time periods. The retrospective collection of the ‘before’ data could also introduce recall bias and inaccurate data. The method of selection and the process that defined the final sample (refusal, withdrawal, exclusion, etc) were explicitly described. The clinical endpoints appear to have been appropriate for detecting the impact of the treatments on the patients’ health status. The main drawback of the analysis was the small sample size, although the authors stated that the demographics and clinical characteristics of the two groups were similar to those recorded in the National Registry.
The conduct and methods of the cost analysis were consistent with the perspective of the patients. A secondary analysis also assessed the costs borne by the health care system. A breakdown of the cost items was reported, but the unit costs and resource quantities were not presented separately; only total costs were reported for each cost category. The price year was reported, which will assist with reflation exercises for other time periods. The resource consumption and costs in the ‘before’ phase were based on retrospective data, which may have reduced the accuracy of this assessment.
Analysis and results:
The study was based on a cost-consequences framework, which precluded the derivation of a summary benefit measure and its subsequent synthesis with costs. The issue of uncertainty was not addressed, and sensitivity analyses were not carried out. The findings were clearly presented and discussed.
Although well described, the study had some methodological limitations relating mainly to its design. The authors’ conclusions should therefore be treated with some caution.
Funded by the Australian National Health and Medical Research Council.
March L M, Barcenilla A L, Cross M J, Lapsley H M, Parker D, Brooks P M. Costs and outcomes of total hip and knee joint replacement for rheumatoid arthritis. Clinical Rheumatology 2008; 27(10): 1235-1242
Other publications of related interest
Chang RW, Pellissier JM, Hazen GB. A cost-effectiveness analysis of total hip arthroplasty for osteoarthritis of the hip. JAMA 1996;275:858-65.
Nelissen RG. The impact of total joint replacement in rheumatoid arthritis. Best Pract Res Clin Rheumatol 2003;17:831-46.
Subject indexing assigned by NLM
Aged; Arthritis, Rheumatoid /economics /surgery; Arthroplasty, Replacement, Hip /economics; Arthroplasty, Replacement, Knee /economics; Australia; Female; Health Expenditures; Humans; Male; Middle Aged; Prospective Studies; Quality of Life; Treatment Outcome
Date bibliographic record published
Date abstract record published