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The Principles of Pharmacoeconomics 499as well as an increase or decrease in cost. Furthermore, the investigators did notconsider the indirect costs of overuse of antibiotics (i.e., resistance of GBS) orparental disutilities for losing an infant or raising a disabled child. Finally, PCR isless likely to be attractive in low-volume hospitals because these investigatorsassumed an on-site laboratory capable of conducting the test would be available, acharacteristic of their hospital. Such assumptions may negate the positive netbenefit of PCR at a different hospital, and these significant assumptions shouldalways be discussed in a pharmacoeconomic paper so that the reader can judgeexternal validity.Cost-Utility AnalysisCUA is an evaluation method similar to that of CEA. CEA costs are measured indollars and outcomes are measured in natural units; however, in CUA the naturalunits are by design a combined estimate of both quantity-of-life and quality-of-life(QoL) or what is often referred to as “utility.” (29) CUA is generally the mostdifficult and costly pharmacoeconomic methodology to utilize and therefore isoften reserved for evaluations of products or interventions that have significanteffects on both QoL and quantity-of-life. In addition, as it measures outcomes inquantity-of-life and QoL, it can be used in a similar fashion to CBA to compareproducts or interventions that result in different outcomes, provided that they bothcan be measured in quantity-of-life and QoL.Detailed discussion regarding the measurement of utility is outside the scopeof this chapter and therefore only a brief explanation will be provided. Utilities aredefined as a patient's preference for experiencing an outcome. Utility values rangefrom 0 to 1, where 0 represents death and 1 represent perfect health. Utilities areelicited from patients through a number of methodologies including questionnaires,visual analog scales, and standard gamble and time trade-off theories. All assumethe simple premise that patients when given a choice will chose the health statewith the highest utility value assigned to it. In addition, values previously used inthe literature or those based upon expert opinion may be used; however, theyshould be used with caution as these values may not be representative of everypatient population.Once determined, these utility values are then multiplied by the extent of timea patient is expected to be in that health state. Any unit of time can be utilized, butmost commonly years of life are used and the resultant outcomes are reported asQALYs. For example, you are evaluating two possible treatments for a lifethreateningfoot infection. Treatment A involves amputation, which costs $20,000but increases life expectancy by 4.5 years at a utility value of 0.60. Treatment B is anaggressive medical treatment with antibiotics, which costs $10,000 and increases lifeexpectancy by only 1.5 years with a utility value of 0.90. Treatment A wouldtherefore cost $20,000/ (4.5*0.4) or 1.8 QALY ¼ $11,111/QALY, where treatment Bwould cost $10,000/1.5*0.9) or 1.35 QALY ¼ $7,407/QALY. Similar to CEA, theincremental increase in cost per unit of outcome could also be calculated ($20,000–$10,000/1.8–1.35 ¼ $22,222 additional dollars will be spent to obtain one additionalQALY with treatment A compared with treatment B). Again, as with CEA, whenprovided with the incremental costs required for one additional outcome, decisionmakersmust determine whether the additional cost required is worth the additionaloutcome achieved.While CUA is a powerful tool among pharmacoeconomic analyses, it is oftendifficult to conduct because of the lack of data required to calculate a QALY in a