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Cost-effectiveness of treating ocular hypertension |
Stewart W C, Stewart J A, Nasser Q J, Mychaskiw M A |
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Record Status 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. CRD summary The objective was to examine the cost-effectiveness of treatment of ocular hypertension (OHT), considering various risk factors. The authors concluded that treatment for OHT was cost-effective only in selected patients with risk factors such as advanced age, high pressures, thin central corneal thickness, and wide vertical cup-to-disc ratios. The study has some limitations that might affect the validity of the authors’ conclusions. Type of economic evaluation Study objective The objective was to examine the cost-effectiveness of treatment of ocular hypertension (OHT), focusing on subgroups of patients with various risk factors. Interventions The treatment strategy was compared with no treatment. The treatment strategy was not described, but the authors referred to a published study, the Ocular Hypertension Treatment Study (OHTS), for these details. The available medications were latanoprost, bimatoprost, travoprost, generic timolol, and brimonidine. Methods Analytical approach:The economic evaluation was based on a Markov model with a five-year time horizon. The authors did not explicitly state the perspective adopted.
Effectiveness data:The clinical data came from selected sources. The bulk of the evidence (i.e. transition probabilities) for the first two years was derived from the OHTS. More data for longer term, progression came from other published studies, including the Early Manifest Glaucoma Trial (EMGT). The key clinical endpoint was the progression rate from OHT to open-angle glaucoma.
Monetary benefit and utility valuations:The derivation of the utility valuations was based on visual acuity data derived from a published study, the details of which were not given.
Measure of benefit:Quality-adjusted life-years were the summary benefit measure. The prevention of one patient from progressing to primary open-angle glaucoma was also reported.
Cost data:The economic analysis included the costs of visits, procedures, and therapy. The resource use data were derived from the OHTS, while the costs were obtained from the Blue Cross/Blue Shield directory from the state of South Carolina, supplemented by data from pharmacies. Using out-of-pocket prices, an average medication price was calculated, because the medication that patients actually received was not specified. The price year was not explicitly reported. Costs were in US dollars ($) and were discounted at an annual rate of 3%.
Analysis of uncertainty:The analysis of uncertainty focused on four risk factors, which were identified in the OHTS: advancing age, higher intra-ocular pressures, thinner central corneal thickness, and wider vertical cup-to-disc ratio. A deterministic one-way sensitivity analysis was also undertaken by varying the following model inputs by ±10%: argon laser trabeculoplasty, number of medications used over five years, and follow-up visits. Results The expected five-year costs per patient were $2,467 without treatment and $5,001 with treatment. The QALYs were 4.45 without treatment and 4.48 with treatment. Thus, under base-case conditions, the incremental cost per QALY was $89,072.
The risk factor analysis indicated that the cost-effectiveness ratio fell below the threshold of $50,000 per unit of benefit in the following scenarios: 20 years or more above the average age of 56 years; 4mmHg or more above the average pressure of 25mmHg; 40μm or more below the average central corneal thickness of 573μm; and wider by 0.2 vertical cup-to-disc ratio or more than the average ratio of 0.4.
The univariate analysis showed that the base-case findings were altered by $10,000 or less in all cases. Authors' conclusions The authors concluded that treatment for OHT was cost-effective only in selected patients with risk factors such as advanced age, high pressures, thin central corneal thickness, and wide vertical cup-to-disc ratios. They noted that future studies should concentrate on further clarifying treatment indications, risk factors, and their associated costs for ocular hypertension. CRD commentary Interventions:The health technologies were not clearly described. The aim of the study was to consider a generic treatment strategy versus no treatment, rather than a specific medication. Thus, the average treatment price and efficacy were calculated, considering all the available medications.
Effectiveness/benefits:The derivation of the clinical data was based on studies that were known to the authors. No information on these studies (their design, patient population, and follow-up) was provided so a critical assessment of the data is not possible. The benefit measure was not clear QALYs were reported in the tables, but the same data were described as the prevention of one patient from progressing to primary open-angle glaucoma in the text.
Costs:The economic viewpoint of the study was not explicitly stated. The categories of costs were reported together with their sources. The unit costs were presented, but resource quantities were not. The price year was not given, which limits the possibility of making reflation exercises for other time periods. The impact of variation in a few cost estimates on the findings was investigated.
Analysis and results:The synthesis of costs and benefits was appropriately carried out using an incremental analysis. The expected costs and benefits were presented. The issue of uncertainty was restricted to a deterministic analysis, which considered only a few inputs. The global uncertainty in the model was not investigated. The authors pointed out some limitations of their analysis, such as the relatively short time horizon and the exclusion of indirect costs.
Concluding remarks:The study has some limitations that might affect the validity of the authors’ conclusions. Bibliographic details Stewart W C, Stewart J A, Nasser Q J, Mychaskiw M A. Cost-effectiveness of treating ocular hypertension. Ophthalmology 2008; 115(1): 94-98 Other publications of related interest Kymes SM, Kass MA, Anderson DR, et al. Management of ocular hypertension: a cost-effectiveness approach from the Ocular Hypertension Treatment Study. Am J Ophthalmol 2006;141:997-1008.
Medeiros FA, Weinreb RN, Sample PA, et al. Validation of a predictive model to estimate the risk of conversion from ocular hypertension to glaucoma. Arch Ophthalmol 2005;123:1351-60.
Gordon MO, Beiser JA, Brandt JD, et al. The Ocular Hypertension Treatment Study: baseline factors that predict the onset of primary open-angle glaucoma. Arch Ophthalmol 2002;120:714-20. Indexing Status Subject indexing assigned by NLM MeSH Aged; Antihypertensive Agents /economics /therapeutic use; Cost-Benefit Analysis; Decision Support Techniques; Glaucoma, Open-Angle /prevention & Health Care Costs; Health Services Research; Humans; Insurance, Health /statistics & Intraocular Pressure; Markov Chains; Middle Aged; Ocular Hypertension /economics /therapy; Quality of Life; Quality-Adjusted Life Years; Risk Factors; Trabeculectomy /economics; United States; control; numerical data AccessionNumber 22008000052 Date bibliographic record published 02/03/2009 Date abstract record published 16/09/2009 |
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