Is Noncontact Normothermic Wound Therapy Cost Effective for the Treatment of Stages 3 and 4 Pressure Ulcers?

Alex Macario, MD, MBA;1 Franklin Dexter, MD, PhD2

Other direct costs included supplies and equipment (see Table 3 footnotes for more detail).41 Complication costs were summed (e.g., antibiotic treatments for systemic infections attributable to the pressure ulcer). Physician professional costs were included.

     NNWT consists of a warming element to which a disposable wound cover is attached. The warming element is provided at no out-of-pocket cost, while the disposable wound cover costs $240.00 per wound cover to acquire. We assumed the wound cover to be used around the clock, with the warming element applied three times (with a minimum of one hour between applications) a day to heat the wound as recommended by the manufacturer. We assumed the wound cover would be used for two days, prior to needing to be replaced, for a daily cost of $120.00. For an eight-week cycle in the Markov model, the total acquisition cost for the NNWT wound cover equaled $6720.00.

     All costs are reported in year 2000 U.S. dollars. We discounted all future costs and QALYs at three-percent per annum in the base case scenario.

     Measurement of health-related quality of life. QALYs include a length of time component (e.g., one year) and a quality-of-life component (i.e., utility). Health utility is the numerical valuation of one’s quality of life on a linear scale from 0.00 (death) to 1.00 (perfect health). For example, one QALY for an individual in perfect health (with a utility = 1.0) for one year (QALY = 1) is considered equivalent to two years in a health state with utility = 0.5 (QALY = 1).

     We were unable to find primary data in the literature for quality-of-life assessments for patients with pressure ulcers.42,43 For this reason, we instead used the Rosser classification of illness states, or Rosser index, to form quality-of-life weights (utilities) for each health state in our model.44

     The quality of life of a patient with a pressure ulcer was determined by assigning levels of disability and distress to each health state. Thus, the Rosser index has two dimensions, disability and distress, and 29 possible health states. The change in health status, or quality adjustment, was combined with the life expectancy of patients to form QALYs. The Rosser and Kind valuation matrix was applied to obtain mean values for patients’ changes in health status.45 The utilities assigned via this method were checked with another scale, the Health Utilities Index-2 multiattribute utility function.46 This scale has dimensions for hearing, speech, vision, emotion, pain, ambulation, dexterity, cognition, and self care. The estimates of utilities used in the model were compiled from these two instruments (Table 4).

     Measurement of life-years. Baseline mortality rates were based on published life tables.47,48 These were modified to reflect that failure of a pressure ulcer to heal is associated with a tripling of mortality.49,50

     Calculation of the cost-effectiveness ratio. Incremental cost effectiveness was calculated by comparing the incremental costs and QALYs with NNWT versus the incremental costs and QALYs obtained with standard treatment. We examined the accuracy of our disease model by comparing the predictions of the model with endpoints observed in clinical studies of treatment of pressure ulcers with those of standard care, not necessarily studies involving NNWT.


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