|
Which antimicrobial impregnated central venous catheter should we use: modeling the costs and outcomes of antimicrobial catheter use |
Marciante K D, Veenstra D L, Lipsky B A, Saint S |
|
|
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. Health technology Two types of antimicrobial catheters aimed at reducing the risk of catheter-related bloodstream infections (CR-BSI) were examined. The catheters were coated with either antiseptic chlorhexidine plus silver sulfadiazine (C-SS) or with the antibiotics minocycline and rifampin (M-R).
Type of intervention Treatment and primary prevention.
Study population The study population comprised a hypothetical cohort of high-risk patients requiring catheterisation. In particular, the study referred to hospitalised adults at high risk of developing a CR-BSI who were likely to require a triple-lumen, noncuffed central venous catheter for at least 3 days. High-risk patients included those in intensive care units (ICU) and those who were immunocompromised.
Setting The setting was a hospital. The economic study was conducted in the USA.
Dates to which data relate The effectiveness data were derived from studies published between 1989 and 2000. The resource use data and costs came from studies published from 1994 to 1999. The price year was 2000.
Source of effectiveness data The effectiveness evidence was derived from a review of completed studies and authors' assumptions.
Modelling A decision tree model was constructed to assess the clinical and economic outcomes associated with the two types of catheters in high-risk patients. The authors said that 25 models were actually constructed to represent patients catheterised for different durations (1 to 25 days). However, the model structure appears to have been the same for all the different durations. The time horizon of the model was the patient's lifetime. A structure of the decision tree was depicted. A catheterised patients was at risk for one of the following events:
remain catheterised without sequelae;
have the catheter removed with no colonisation, local infection, or CR-BSI;
have a colonised catheter removed with no evidence of local infection or CR-BSI;
have a colonised catheter removed with evidence of local infection, but no CR-BSI; or
have a catheter removed with CR-BSI.
Outcomes assessed in the review The outcomes estimated from the literature were the rates of local infection given colonisation, death due to CR-BSI, life expectancy, and utility. Life expectancy was obtained by assessing the rate of patients who would have a central venous catheter, who would develop a CR-BSI, and who would die as a result of the CR-BSI. Also, by estimating the proportions of patients who would die within 1, 2 or more years of catheterisation.
Study designs and other criteria for inclusion in the review A formal review of the literature was not undertaken. One of the primary studies was a clinical trial. Information on the other sources was not provided.
Sources searched to identify primary studies Criteria used to ensure the validity of primary studies Methods used to judge relevance and validity, and for extracting data Number of primary studies included Thirteen primary studies provided the evidence.
Methods of combining primary studies Investigation of differences between primary studies Results of the review The rate of local infection given colonisation was 0.05 in the reference case (C-SS), 0.40 in the M-R-favoured case, and 0 in the C-SS-favoured case.
The rate of death due to CR-BSI was 0.14 in the reference case, 0.24 in the M-R-favoured case, and 0.04 in the C-SS-favoured case.
Life expectancy was 15 years in the reference case, 20 years in the M-R-favoured case, and 10 years in the C-SS-favoured case.
The utility weight was 0.80 in the reference case, 0.90 in the M-R-favoured case, and 0.70 in the C-SS-favoured case.
The rate of patients who would have a central venous catheter was 60%.
The proportion of patients who would develop a CR-BSI was 5%.
The rate of those who would die as a result of the CR-BSI was 15%.
Twenty-seven per cent of patients would die within 1 year of catheterisation, 5% would die within 2 years of catheterisation, and 67% would live an additional 22 years.
Methods used to derive estimates of effectiveness The authors made some assumptions that were used in the decision model.
Estimates of effectiveness and key assumptions The authors assumed the following:
the risk of death after CR-BSI was the same for the two catheters;
there were no adverse outcomes associated with catheter colonisation (without local infection) or catheter removal in the absence of CR-BSI;
the survival experience of high-risk patients requiring central venous catheterisation was similar to the survival of patients hospitalised in an ICU;
the primary benefit of M-R catheters was the reduced risk of local infection and CR-BSI;
any other complications were equally likely for M-R and C-SS catheters.
Measure of benefits used in the economic analysis The summary benefit measure used was the quality-adjusted life-years (QALY). These were estimated from the decision model. An annual discount rate of 3% was applied as patient survival was assessed over a long timeframe. The utility weights were derived from the literature. Given that quality of life estimates specific to patients requiring central venous access were not available and much of the study population suffered from cardiovascular disease or cancer, the health states of lymphoma, leukaemia and congestive heart failure were used to obtain quality of life. However, few details of the source of such weights were provided.
Direct costs Discounting was not relevant since the costs were incurred during a short time. The unit costs were not presented separately from the quantities of resources used and a detailed breakdown of the cost items was not provided. The cost analysis included only the additional cost of an M-R catheter, the cost of CR-BSIs, and the cost of treating a local infection. The cost/resource boundary of the health care payer was adopted. Both the resource use data and costs were estimated from published studies. Therefore, few details on the methods used to assess the costs were provided. The cost of a CR-BSI was assumed to have been the same regardless of the survival outcome. All the costs were presented in 2000 values using the medical care component of the Consumer Price Index.
Statistical analysis of costs The costs were treated deterministically in the base-case.
Indirect Costs The indirect costs were not included.
Sensitivity analysis Univariate sensitivity analyses were conducted to determine the robustness of the estimated cost-utility ratios in MR- or CSS-favoured scenarios (all model inputs were set favourable to either catheter type). A multivariate sensitivity analysis (Monte Carlo simulation with 10,000 iterations), where all model inputs were attributed a probabilistic distribution, was also carried out.
Estimated benefits used in the economic analysis During the first 7 days of catheterisation, no cases of CR-BSI occurred among M-R catheter patients.
The expected QALYs gained with M-R catheters over C-SS catheters were 0.009 (95% confidence interval, CI: -0.009 - 0.016) for patients catheterised 8 days, 0.03 (95% CI: 0.007 - 0.053) for patients catheterised 15 days, and 0.034 (95% CI: 0.009 - 0.059) for patients catheterised 22 days.
Cost results The expected costs associated with M-R catheters over C-SS catheters were -$67 (95% CI: 88 - -165) for patients catheterised 8 days, -$260 (95% CI: -29 - -580) for patients catheterised 15 days, and -$294 (95% CI: -40 - -654) for patients catheterised 22 days. Therefore, the M-R catheter was always associated with cost-savings.
Synthesis of costs and benefits Incremental cost-utility ratios were calculated to combine the costs and QALYs of the two strategies under evaluation. However, the cost per QALY was not actually estimated because the M-R strategy dominated the C-SS strategy, which was both less effective and more costly.
The multivariate sensitivity analysis showed that the probability that the M-R strategy was cost-effective (cost per QALY below the threshold of $50,000) was 91% after 8 days. The probability that the M-R strategy was cost-saving (dominant) was 97.4% for 13 or more days.
The impact of variations of single estimates, while keeping all others constant, was small.
The parameter with the strongest individual impact on the final cost-effectiveness results was the relative risk of a CR-BSI.
Only when C-SS-favouring estimates were used were M-R catheters not cost-effective or not cost-saving, until used in patients catheterised for more than 2 weeks.
Authors' conclusions Central venous catheters coated with minocycline plus rifampin (M-R) were cost-effective for patients catheterised for at least one week, and cost-saving when patients were catheterised for at least 2 weeks.
CRD COMMENTARY - Selection of comparators The authors justified the choice of the comparator. The C-SS catheter was selected because it had recently received approval from the Federal Drug Administration. Uncoated catheters were not considered as a relevant strategy because infection control experts recommended the use of a coated catheter in high-risk patients. You should decide whether the C-SS catheter is a valid comparator in your own setting.
Validity of estimate of measure of effectiveness The effectiveness evidence came from published studies. A review of the literature does not appear to have been conducted. In addition, with the exception of a clinical trial, which was the main source of the evidence, the primary studies were not described. The methods used to extract the primary data and then to combine them were not reported. However, reasons for the choice of the parameters were described. Some assumptions were also made. The issue of uncertainty was investigated satisfactorily in the sensitivity analysis, where alternative scenarios were considered.
Validity of estimate of measure of benefit The use of QALYs as the summary benefit measure was appropriate as it captured the impact of the intervention on the patients' health. Discounting was applied, as recommended in the USA. The utility weights were derived from the literature, but no information on the preferences used was provided.
Validity of estimate of costs The authors adopted a very limited perspective and included only the costs strictly related to the initial hospital management of disease. The authors noted that the adoption of a wider perspective and the inclusion of indirect costs would have further favoured the M-R option. As the costs were derived mainly from published studies, details on resource use and unit costs were not given. This limits the possibility of replicating the study. Discounting was not conducted because only the initial hospital costs were considered. The price year was reported, which makes reflation exercises in other settings easy. Overall, there was limited information on the cost analysis.
Other issues The authors made some comparisons of their findings with those from other studies. The authors stated that the use of trial data limited the generalisability of their findings. They also noted that they were unable to assess the cost-effectiveness of C-SS versus M-R catheters in patients catheterised less than 8 days, owing to the lack of trial data. Further, the risk of complications was not considered in the model. Although data from different sources were used, the results of the model proved to be robust to several changes in baseline inputs, as the sensitivity analysis showed.
Implications of the study The study results suggested "policies for the use of antimicrobial catheters in high-risk patients should reflect patients' expected duration of catheterisation".
Bibliographic details Marciante K D, Veenstra D L, Lipsky B A, Saint S. Which antimicrobial impregnated central venous catheter should we use: modeling the costs and outcomes of antimicrobial catheter use. American Journal of Infection Control 2003; 31(1): 1-8 Other publications of related interest Darouiche RO, Raad II, Heard SO, et al. A comparison of two antimicrobial-impregnated central venous catheters. New England Journal of Medicine 1999;340:1-8.
Pittet D, Tarara D, Wenzel RP. Nosocomial bloodstream infection in critically ill patients. Excess length of stay, extra costs, and attributable mortality. JAMA 1994;271:1598-601.
Veenstra DL, Saint S, Sullivan SD. Cost-effectiveness of antiseptic-impregnated central venous catheters for the prevention of catheter-related bloodstream infection. JAMA 1999;282:554-60.
Indexing Status Subject indexing assigned by NLM MeSH Anti-Infective Agents /administration & Bacteremia /prevention & Catheterization, Central Venous /adverse effects /economics /methods; Catheters, Indwelling /economics /microbiology; Chlorhexidine /administration & Cost-Benefit Analysis; Decision Support Techniques; Drug Delivery Systems; Humans; Middle Aged; Minocycline /administration & Quality-Adjusted Life Years; Rifampin /administration & Sensitivity and Specificity; Silver Sulfadiazine /administration & Time Factors; United States; control; dosage /economics; dosage /economics; dosage /economics; dosage /economics; dosage /economics AccessionNumber 22003000741 Date bibliographic record published 28/02/2005 Date abstract record published 28/02/2005 |
|
|
|