Cost-Effectiveness of Transesophageal Echo

Abstract & Commentary

Synopsis: TEE-guided therapy may not be suitable for patients at high risk for complications, such as the immunosuppressed, subjects using intravenous drugs, or those with prosthetic valves.

Source: Rosen AB, et al. Ann Intern Med 1999;130: 810-820.

Staphylococcus aureus bacteremia is relatively common in patients who have had an indwelling intravascular catheter during hospitalization. A frequent therapeutic approach is to routinely treat such individuals for 4-6 weeks with intravenous antibiotics. Rosen and colleagues from Duke University Medical Center, using state-of-the-art cost-effectiveness methodology and including decision analysis modeling, assessed three approaches to the management of catheter-related S. aureus bacteremia in patients who were otherwise uncomplicated. The primary goal was to see whether transesophageal echo (TEE) assessment would be a reasonable cost-effective alternative to the standard protocol antibiotic treatment course. Rosen et al modeled three management strategies: TEE in all patients, with two weeks of antibiotics in those not found to have endocarditis, and at least a four-week antibiotic course in those documented to have vegetations consistent with endocarditis; a routine policy of two weeks of intravenous antibiotics; and four weeks of oral antibiotics. All relapses were assumed to be due to ineffective therapy; such patients would be retreated with prolonged therapy. The three approaches all used combined inpatient and outpatient antibiotic therapy.

Rosen et al used the Duke endocarditis database, as well as an extensive literature review, to determine the natural history of catheter-associated bacteremia, including complications and co-morbidity, and the natural history and mortality in subjects with bacteremia and endocarditis, by pooling all available data. Event probabilities were derived from the literature. It was determined that a short antibiotic course relapse rate would be 6% vs. 2.6% for individuals receiving a long course of therapy. TEE was considered to be highly sensitive and specific (> 95%). Cost estimates were derived from an estimate of direct medical costs, as well as productivity estimates due to loss of work or death. Hospitalization costs were derived from Duke Hospital. Quality-adjusted life expectancy (QUALY) costs were used as the effectiveness end point in the study, and were derived for a hypothetical cohort of patients with a variety of co-morbidities, including diabetes, end-stage renal disease, and cardiac disease. Quality of life was assessed using a measure of patient preference for health outcome, known as a utility. Incremental cost-effectiveness ratios for each strategy were derived by comparing TEE to the two treatment approaches. Sensitivity analyses were carried out for a large number of variables over a wide range of values, including stroke, valve surgery, hospitalization for endocarditis, and prevalence of endocarditis.

The results indicated that the TEE strategy was an efficacious and cost-effective strategy for the management of S. aureus bacteremia in patients meeting the study criteria (immunosuppressed subjects, IV drug users, and those with prosthetic valves were excluded). While both the long-course strategy and TEE were efficacious when compared to the short-course strategy, the cost of the TEE strategy was low, confirming that the TEE approach had the best incremental cost-effectiveness of the three management approachs. Rosen et al estimated that for every QUALY gained by using an empiric four weeks of antibiotics instead of TEE, there would be a cost of more than $1.6 million. Sensitivity analysis using widely variable rates of prevalence of endocarditis showed cost savings for the short course antibiotic approach only at high rates of valve infection. Similarly, the empiric long-course therapy was associated with high costs for all sensitivity analyses, particularly when low rates of endocarditis were factored in. The cost of a TEE procedure did not materially affect the analysis for either antibiotic strategy. Rosen et al concluded that, "for most clinically realistic combinations of endocarditis prevalence and short course relapse rates, the TEE strategy was the cost effective alternative to the two other management strategies."

While the empirical long-course therapy demonstrated maximal effectiveness, scarcely different from the TEE approach, the cost of the TEE strategy was much less, in spite of comparable clinical outcomes. An important assumption was that no cases of actual endocarditis would be cured by the short-course therapy. Rosen et al believe that the TEE approach could save more than $140 million in U.S. health expenditures when compared to empiric long-course antibiotics. They conservatively estimate that there are approximately 35,000 cases of S. aureus catheter-associated bacteremia per year; the TEE strategy is very cost-effective, with a cost of $5000 per QUALY. Rosen et al stress that this analysis is only for patients without complications who have positive blood cultures and no noncardiac sources of infection. They conclude that TEE-guided therapy may not be suitable for patients at high risk for complications, such as those immunosuppressed, subjects using intravenous drugs, or those with prosthetic valves.

Comment by Jonathan Abrams, MD

This interesting analysis is quite convincing that TEE is an appropriate management strategy for individuals with bacteremia associated with placement of an intravenous line. If endocarditis is excluded on the echo, a short course of antibiotics is appropriate, given the low likelihood of endocarditis being present or developing subsequently. For those individuals with vegetations, at least four weeks of antibiotics are indicated. Thus, a long course of protracted antibiotics could be avoided in the large number of patients who have bacteremia but who do not have endocarditis; conversely, short-course (2-week) therapy is safe only in individuals without endocarditis. The latter approach would not be cost-effective if the prevalence of endocarditis is moderate or higher. Rosen et al conclude that the "use of the high tech option" instead of standard practice may result in substantial savings for the U.S. healthcare system.

This study is supported by an editorial written by Milton Weinstein of Harvard, who makes the comment that high-tech approaches may be appropriate and cost-effective for certain medical conditions, wherein a preventive or treatment strategy represents good value for the money. He underlined the importance of similar decision-making analyses for cost-effectiveness, and applauds the use of this approach for other clinical conditions. It would appear that the modest cost of a TEE is well worth it, as patients can be immediately risk stratified. This is concordant with the literature supporting the initial use of TEE when endocarditis is suspected, in the absence of in-dwelling catheters; a negative study is highly concordant with the absence of endocarditis and eliminates the need for protracted antibiotic therapy in relatively routine cases. While it may be that TEE is not available in all institutions, this is probably not a major problem, since in hospitals that are using intravenous lines, it is more than likely that TEE is available. This test should be used earlier and more widely on the basis of these findings. As Weinstein points out, physicians and healthcare providers must learn which technologies and devices are cost-effective based on careful studies to obviate the knee-jerk response that spending money for a high-tech procedure or therapy should be avoided at all costs.

The most cost-effective approach to S. aureus bacteremia in hospitalized patients is:
a. six weeks of IV antibiotics.
b. two weeks of IV and two weeks of oral antibiotics.
c. immediate TEE with antibiotic course based on results.
d. two weeks of antibiotics.