Page 74 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

42 PART 1: An Overview of the Approach to and Organization of Critical Care

Long-term acute care (LTAC) facilities are playing an increasing stents have a different cost-effectiveness ratio when compared to no PCI
role in the care of patients after critical illness. Many of these facili- as opposed to standard therapy with PCI and bare metal stent delivery.
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ties accept patients directly from the ICU, even before liberation from Standard therapy should also represent the least expensive strategy
mechanical ventilation. Transferring patients to LTACs, as an example of possible. Recognizing that there is variability in practice between physi-
a process of care, results in a reduced length of stay for the originating cians, the ATS guidelines simplified matters by recommending that best
hospital, and may encourage the assignment of some cost savings as a practice be the comparator of choice for cost-effectiveness studies.
result of that reduced length of stay. While it is possible that this pro-
cess of care is overall less expensive from the perspective of society, this
determination would need to include all costs of care incurred by the DISCOUNTING
patient in the LTAC along with costs of care at the originating hospital. Discounting costs over time is another important element in the
Without this accounting step, the cost of patient care is simply shifted analysis. When we borrow money, we must pay it back with interest.
https://kat.cr/user/tahir99/
to the LTAC, rather than inherently reduced. Likewise, introducing an This is because money is worth more now than it will be in the future.
intermediate care unit in the hospital may decrease ICU costs, but not For example, $10 is more valuable now than $10 delivered at a rate of
have the same financial benefit from the standpoint of the hospital. The $1 per year for the next 10 years. It follows, to repay $10 over the next
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importance of perspective cannot be overstated. 10 years, we would be required to pay more than $1 per year. Worldwide
economic growth is occurring at approximately 3% per year, and there-
COST ESTIMATES AND GUESSES fore the PCEHM and ATS recommend that all costs be discounted at a
3% rate per annum.
Not all costs in a cost-effectiveness analysis are measured empirically. Equally important, effects should also be discounted. Analogous to
One reason is that pricing for a treatment may not be established at the the borrowed money example, the benefit of one person living 10 addi-
time of the analysis. In this circumstance, an educated “best guess” is tional years is not equivalent to 10 persons each living one additional
made, with consideration of preliminary pricing set by company. year. Failure to discount effects incurs the Keeler-Cretin procrastination
Perhaps surprisingly, estimates of costs may not even have a major paradox, wherein we would forever favor health care programs that take
impact on the analysis. To investigate how sensitive a cost-effectiveness place sometime in the future. Effects are therefore discounted at 3%,
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ratio is to cost estimates, the completed model is exposed to a sensitivity the same rate as costs.
analysis. As long as the estimated costs have little effect on the overall
conclusions, estimates are acceptable and the finding is considered robust.
ROBUSTNESS AND SENSITIVITY ANALYSIS
COST STREAMS When we perform an RCT, our primary conclusion is a statement of
effect: Did the new therapy change the outcome of interest? Statistical
When the cost of therapy is computed, the duration of the costs attributed testing for significance tells us which therapy arm is better, but not how
to the therapy must also be considered. For example, if our new therapy much better. Consider the case of inhaled nitric oxide among neonates
allows more people to leave the ICU, but causes a higher incidence of with respiratory failure, for which an RCT found a reduced chronic
renal failure requiring long-term dialysis, this needs to be included in the lung disease (7% vs 20%; p = 0.02) and reduced use of ECMO (38%
accounting. In producing a survivor, one must also take responsibility for vs 64%; p = 0.006). This does not mean that exactly 26 patients avoid
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the cost of maintaining survival, which means following the cost streams ECMO therapy for every 100 neonates treated. Rather, it tells us that
for an appropriate length of time. Furthermore, if chronic renal failure our best estimate is that 26 patients are spared. If we in turn presume
leads to a lower quality of life, the new therapy will be doubly penalized, a binomial distribution around the rate, we can generate confidence
both for the cost of the dialysis and for the reduced quality-adjusted intervals for the estimate. The confidence intervals might now tell us
survival. This concept is known as the cost of survivorship. that the new therapy prevents between 18 and 34 ECMO runs per 100
neonates treated, but cannot tell us where the true value falls within
COST MEASUREMENT that range.
On the other hand, in cost-effectiveness analysis, it is a primary
For the costs we choose to measure, we must decide what represents interest to describe the magnitude of effects and costs, yielding a cost-
true cost. True costs might be assumed to be those generated by formal effectiveness ratio. To do this, we generate a base case and then perform
cost-accounting mechanisms. For example, the cost of a complete blood a sensitivity analysis. The base case comes from our best point estimates
count includes the wage rate for and time spent by the employee who of cost and effect. Thereafter, we vary our estimates across their range
drew the blood, the cost of the tube, and some tiny amortized fraction of probabilities to determine the extent to which the cost-effectiveness
of the cost of the equipment upon which the test is run. In economics, ratio varies. This exercise is known as a sensitivity analysis and can be
this approach is called microcosting. However, detailed information performed with multiple variables simultaneously. If, despite varying
such as this is rarely available as part of a cost-effectiveness analysis. several or all variables across their stochastic distributions, there is
Instead, a frequently used approach is to collect hospital charges and minimal change in the final ratio, we have confidence in the robustness
adjust them by the hospital- or department-specific cost-to-charge of our estimate.
ratio. Comparisons between department-specific cost-to-charge ratio- The sensitivity analysis can also be used to determine which model
adjusted charges and estimates generated from a formal cost-accounting parameters need to be measured most accurately. For example, the cost-
system show good correlation when assessing patients in groups. effectiveness ratio may be particularly sensitive to estimates of ICU costs,
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Agreement is worse when comparing individual patients and when but relatively insensitive to expected costs of postdischarge resource use.
using hospital-specific ratios; however, cost-effectiveness analyses rely In this situation, ICU costs need to be measured carefully, while postdis-
on average grouped estimates, and therefore department-specific esti- charge resource use can be estimated with less rigor. Alternatively, a sensi-
mates are adequate for estimating hospital costs. tivity analysis can be pinned to cost-effectiveness threshold (eg, $50,000)
and then vary other parameters to show the ceiling of costs under which
DEFINING STANDARD CARE a given therapy would still be considered cost-effective. An example of
this approach was used in the evaluation of lung-protective ventilation for
The comparison group in the analysis, standard therapy, must reflect acute lung injury. Even at an investment level of $9482 per patient with
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contemporary clinical practice to yield meaningful conclusions. For acute lung injury, an intervention that increased adherence to lung-pro-
example, percutaneous coronary interventions (PCI) with drug-eluting tective ventilation from 50% to 90% would be considered cost-effective. 34

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