David Wonderling

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The cost-effectiveness of thromboprophylaxis
David Wonderling Senior Health Economist National
Collaborating Centre for Acute Care Royal
College of Surgeons of England
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Content

• Role of cost-effectiveness analysis
• Determinants of the cost-effectiveness of VTE
  prophylaxis
• Some evidence The cost-effectiveness of VTE
  prophylaxis in surgical patients
• Discussion remaining uncertainties

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Why consider cost-effectiveness?

• NOT about saving the government money
• cost-effectiveness
• value for money
• getting the most health gain from the resources
  available
• If the NHS spends more on one thing, it has to do
  less of something else
• The opportunity cost is the value of the best
  alternative use of resources
• Could we do more good by spending money in other
  ways?

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Quality-adjusted life-year (QALY)
Health-related Quality of life
Perfect health
1.0
Intervention A
Intervention B
0.5
0
Death
Years
1
2
QALYs area under the curve
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How to measure cost-effectiveness

• NICEs cost-effectiveness criterion
• incremental cost-effectiveness is less than
  20,000 per QALY gained
• ½ QALY for every 10,000 spent

4.No prophylaxis 3.Mechanical 2.LMWH
1.MechanicalLMWH
ICER 1
ICER 3
ICER 2
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What health effects?

• QALYs Mortality and quality of life
• Determined by
• Symptomatic DVTs
• Symptomatic PEs (fatal and non-fatal)
• Major bleeding (fatal and non-fatal)
• Post-thrombotic syndrome (PTS)

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What costs?

• Costs
• Drugs, stockings, other consumables
• Prophylaxis administration e.g. nurse time
• Treatment of adverse events (major bleeds)
• Cost savings
• Treatment of symptomatic VTEs
• Treatment of PTS

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Calculating cost-effectiveness.For each
prophylaxis strategy

• The incidence of each event
• Baseline risk x Relative Risk
• Health outcome
• Incidence x QALYs lost
• Cost outcome
• Incidence x treatment cost
• Sum up health and cost outcomes
• Calculate incremental cost-effectiveness ratios
  compare with threshold
• Repeat for different populations with different
  baseline risks

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Cost-effectiveness and risk

• Effectiveness cost-effectiveness of prophylaxis
  is determined by baseline risk of VTE
• Lowest risk
• health benefits are outweighed by health harms
• Higher risk
• Net health benefits are outweighed by opportunity
  costs
• Highest risk
• opportunity costs are outweighed by health
  benefits

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Cost-effectiveness of surgical VTE prophylaxis
the NICE guideline

• Based on the guideline systematic review
• Directed by the Guideline Development Group
• Public consultation
• Key assumptions for base case analysis
• Observed reductions in DVTs lead to commensurate
  reductions in fatal non-fatal PEs
• Observed increases in Major bleeds lead to
  commensurate increases in fatal bleeds
• Post-thrombotic syndrome is not averted by
  prophylaxis

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Results of base case analysisby baseline risk
level
Risk of symptomatic VTE with no prophylaxis
THR
Mechanical -only Prophylaxis
MAS
Combination Prophylaxis
Risk of major bleeding with no prophylaxis
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Sensitivity analysis prophylaxis is only 50 as
effective for fatal events
Risk of symptomatic VTE with no prophylaxis
THR
MAS
Risk of major bleeding with no prophylaxis
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Sensitivity analysis PTS is averted
Risk of symptomatic VTE with no prophylaxis
THR
MAS
Risk of major bleeding with no prophylaxis
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Discussion

• A single type of prophylaxis is cost-effective in
  surgery patients
• (And cost-saving in many subgroups)
• Mechanical prophylaxis is preferred over LMWH
  unless
• baseline risk of major bleeding is negligible
• long-term outcomes are assumed (PTS is averted)
• there are differential effects on fatal pulmonary
  embolism

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Discussion 2

• Whether combination prophylaxis is cost-effective
  is highly sensitive to
• the extent that fatal events are averted
• the extent that long-term events are averted
• baseline risk of VTE
• baseline risk of major bleeding
• Extended duration LMWH prophylaxis is only
  cost-effective if
• long-term effects (PTS) are assumed
• Incidence of fatal PE is high

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• NICE Guideline on venous thromboembolism
  (surgical)
• National Collaborating Centre for Acute Care.
  Venous thromboembolism. Clinical guideline no
  46. National Institute of Clinical Excellence,
  London 2007. http//guidance.nice.org.uk/CG46
• Guideline Development Group
• Tom Treasure (Chair), Nigel Acheson, Ricky Autar,
  Colin Baigent, Kim Carter, Simon Carter, David
  Farrell, David Goldhill, John Luckit, Robin
  Offord, Adam Thomas.
• NCC-AC staff Enrico de Nigris, Jennifer Hill,
  Philippa Davies, Carlos Sharpin, Saoussen Ftouh,
  Peter Katz, Arash Rashidian.
• Funding
• National Institute for Health and Clinical
  Excellence, London, England