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Surgery for spinal stenosis
Submit responseThe favorable conclusions drawn by the authors of this randomized controlled study should be viewed in a more sceptical light. The graph showing a clinical benefit at 2 years had the vertical axis amputated, thus expanding the apparent improvement. The real improvement was very modest even for degenerative spondylolisthesis (QALY gain 0.23). Further, at 2 years 26% of patients in the control arm were on opiates, compared to 73% of those following surgery.
The opposite conclusion is more likely: Opiates as used (details and intensity not described) provided a slight improvement and that surgically treated patients had an even greater need for pain control. In fact, much greater reductions in pain are commonly achieved with opiate treatment of adequate dose and there is little in this study to suggest surgery is effective.
I do commend the authors in undertaking a randomized study since the number of proven surgical procedures is regrettably few.
References
1. Anna N.A. Tosteson, Jon D. Lurie, Tor D. Tosteson, Jonathan S. Skinner, Harry Herkowitz, Todd Albert, Scott D. Boden, Keith Bridwell, Michael Longley, Gunnar B. Andersson, Emily A. Blood, Margaret R. Grove, James N. Weinstein for the SPORT Investigators Surgical Treatment of Spinal Stenosis with and without Degenerative Spondylolisthesis: Cost-Effectiveness after 2 Years Ann Intern Med 2008; 149: 845-853
Conflict of Interest:
None declared
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IN RESPONSE:
Submit responseWe thank Drs. Shusterman and Erder, for their comments which highlight both the challenge inherent in utilizing any single threshold as a benchmark for ascribing value to health care interventions and the pitfalls in adjusting for inflation and converting between currencies. If one first inflates from mid-1990 to mid-2004 Canadian Dollars (an adjustment of 1.319 (1)), then the “costly” $100,000 threshold (2) becomes $131,900. Converting between 2004 Canadian and US Dollars (1.322 Canadian Dollars per US Dollar as of July 1, 2004 (3)), one achieves a value of $131,900/1.322=$ 99,773 or approximately $100,000 in 2004 US Dollars.
To overcome relying on a single benchmark, we showed results for the most important sensitivity analyses using a cost-effectiveness acceptability curve, which graphed the proportion of times the cost per QALY gained achieved willingness-to-pay thresholds ranging from $20,000 to $300,000 (4). Such graphical presentations should be helpful to those skeptical about the use of any particular cost-effectiveness benchmark. This methodology was also useful for demonstrating the marked impact that higher surgery costs have on surgery’s value- an issue raised by Dr. Balestra's comment. Our costing approach utilized national standardized Medicare payment amounts as a proxy for actual resource tilization. Thus, the surgery costs in our analysis were lower than what many private insurers pay. When surgery’s cost was based on 70% of the amount hospitals billed to Medicare (a higher amount that what Medicare actually pays), in only a small minority of samples did the cost per QALY gained for surgery fall below $100,000.
The role that our costing approach had on comparisons between instrumented and non-instrumented fusion surgery warrants comment. Our report of no difference in cost between fusion types is largely an artifact of our costing approach, because Medicare payment amounts are minimally different for these surgical alternatives. While it is notable that no statistically significant health outcome differences were observed over 2-years between fusions types, further follow-up of SPORT participants using several approaches to costing will be important for understanding the long-term value of surgery.
Although the SPORT protocol specified a minimum symptom duration of 12 weeks, we are aware of no referral restrictions in place at participating centers. Prior treatments received by SPORT observational cohort participants have been described (5), and may be indicative of varied referral pathways. Our study was not designed to address the optimal symptom duration prior to surgery.
References
(1) Inflation Calculator from Bank of Canada accessed at: http://www.bankofcanada.ca/en/rates/inflation_calc.html, February 3, 2009.
(2) Laupacis A, Feeny D, Detsky AS, Tugwell PX. How attractive does a new technology have to be to warrant adoption and utilization? Tentative guidelines from using clinical and economic evaluations. Can Med Assoc J. 1992;146:473-481.
(3) Canada / U.S. Foreign Exchange Rate from St Louis Federal Reserve accessed at: http://research.stlouisfed.org/fred2/data/EXCAUS.txt, February 3, 2009.
(4) Tosteson ANA, Lurie JD, Tosteson TD, Skinner JS, Herkowitz H, Albert T, et al. Surgical treatment of spinal stenosis with and without degenerative spondylolisthesis: cost-effectiveness after 2 years. Ann Intern Med. 2008;149:845-853.
(5) Cummins J, Lurie JD, Tosteson TD, Hanscom B, Abdu WA, Birkmeyer NJO, Herkowitz H, Weinstein J. Descriptive epidemiology and prior healthcare utilization of patients in the Spine Patient Outcomes Research trial’s (SPORT) three observational cohorts- Disc herniation, spinal stenosis and degenerative spondylolisthesis. Spine 2006;31:806-814.
Conflict of Interest:
None declared
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Cost-Effectiveness of Spinal Stenosis Surgery
Submit responseTO THE EDITOR: We read with interest the article by Tosteson and colleagues (1) regarding the cost-effectiveness of surgical treatment of spinal stenosis with or without degenerative spondylolisthesis. However, we note that the health economic conclusions of the article may be more favorable than suggested by the authors based on a need to adjust the frame of reference to American dollars and adjust for inflation. This is because the authors refer to a paper by Laupacis et al (2) as a guide to determining whether a health intervention is considered “costly” or not. Two factors need to be kept in mind about this reference.
First, the Laupacis et al guidelines for interpreting health economic data were calculated in Canadian dollars at a time when the American dollar was stronger. Second, the Laupacis et al guidelines were based on the Canadian dollar in 1990, 14 years before the year used to standardize the health costs by Tosteson et al (2004). Inflation over that time period means that the value of a dollar in 2004 was not the same as in 1990. Laupacis et al suggest that interventions over CAN $100,000 per quality-adjusted life year (QALY) gained provide “weak evidence for adoption”, i.e. are “costly”. Based on the exchange rate in mid-1990 this would equate to U.S. $85,771 at that time (3). Adjusting for inflation in the United States between mid-1990 and mid-2004 increases this to U.S. $123,964 (4). Based on this standard, both of the interventions studied by Tosteson et al (spinal stenosis surgery and spondylolisthesis surgery) could be considered cost-effective after converting to U.S. dollars and accounting for inflation.
References
1. Tosteson ANA, Lurie JD, Tosteson TD, Skinner JS, Herkowitz H, Albert T, et al. Surgical treatment of spinal stenosis with and without degenerative spondylolisthesis: cost-effectiveness after 2 years. Ann Intern Med. 2008;149:845-853.
2. Laupacis A, Feeny D, Detsky AS, Tugwell PX. How attractive does a new technology have to be to warrant adoption and utilization? Tentative guidelines from using clinical and economic evaluations. Can Med Assoc J. 1992;146:473-481.
3. FX converter: currency converter for 164 currencies. Accessed at http://www.oanda.com/convert/classic on 11 January 2009.
4. CPI inflation calculator. U.S. Bureau of Labor Statistics. Accessed at http://data.bls.gov/cgi- bin/print.pl/data/inflation_calculator.htm on 11 January 2009.
Conflict of Interest:
None declared
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SPORT study/cost effectiveness analysis
Submit responseI really appreciated this article estimating the cost effectiveness of back surgury. As a retired General Internist who has treated many patients with back pain at the WRJct VA over many years in both acute and chronic settings ("walk-in" clinic; emergency room; scheduled GMC), and who has some familiarity with Richard Deyo's seminal work on back pain, several questions come to mind.
1. You mention that most patients were symptomatic for at least 6-7 months prior to study in "Multidiscinplinary Spine Clinics." Did each study site allow direct scheduled appointments, unscheduled "walk-in" evaluations, or emergency room evaluations(i.e., direct access) to Spine Clinic? Asked differently, did each Spine Clinic only accept referrrals from PCPs, or Emergency Room Professionals prior to Spine Clinic evaluation and what was the mean time from initial symptom onset to initial Spine Clinic evaluation and treatment entry (disease duration)? The reason for this interest is to determine if "referral status" vs "Spine Clinic status" is the better measure of surgical efficacy at 2 years, and to determine if an increased "delay to surgury" is a predictor of surgical efficacy by allowing operation to only the most durably symtomatic pain sufferers? Is there a pain duration that might represent an inflection point in the surgical efficicay vs time-to-treatment curve?
2. Your thoroughness in detailing medical costs is very impressive. Yet the largest single ticket item, and the only truly "discriminating" cost among the four treatment arms in Table 2 is "Surgery." As a General Internist, I would be particularly interested in a breakdown of "Surgical cost" into "hospital charges-Medicare re-imbursable", "hospital charges-negotiated reduction", "hospital charges-patient copay", "hospital charges -patient balance billed", and "physician charges." Asked differently, how well do Medicare payment schedules (Part A plus Part B), reflect private insurer costs plus patient costs (total costs) and surgical cost- effectiveness? Is surgical cost effectiveness in younger, Medicare ineligable patients, better, worse, similar?
References
1. Anna N.A. Tosteson, Jon D. Lurie, Tor D. Tosteson, et al. For the SPORT Investigators Surgical Treatment of Spinal Stenosis with and without Degenerative Spondylolisthesis: Cost-Effectiveness after 2 Years Ann Intern Med 2008; 149: 845-853
Conflict of Interest:
None declared