University:
Kentucky State University
Course:
ECO 301 | Microeconomics
Academic year:

2021
Views:

23

Pages:

44
Author:

slypery5hy

Cost-Utility Analysis Cost-Utility Analysis (CUA) • Some consider CUA a subset of CEA because the outcomes are assessed using a special type of clinical outcome measure, usually the qualityadjusted life-year (QALY) • CUA take patient preferences (utilities) into account when measuring health consequences • The most common outcome unit used in CUA is the QALY, which incorporates both the quality (morbidity) and quantity (mortality) of life • Other outcome units that are seen less frequently include qualityadjusted life months (QALMs) and healthy-year equivalents (HYEs) CUA • Advantages: • different types of health outcomes & diseases with multiple outcomes of interest can be compared using one common unit (i.e., QALY) (unlike CEA) • CUA incorporates morbidity and mortality into one common unit without estimating the monetary value of these health outcomes (unlike CBA) • Disadvantage • it is difficult to determine an accurate utility or QALY value • Publications using CUA are still less common than those using CEA Overview of CUA • For some research questions, utility adjustments are not needed • Example: if 2 pharmaceutical products • have different outcomes based on no. of life-years saved (LYS) • but the quality of each year of life for those on 2 drugs are thought to be the very similar • Then, quality adjustment may not be warranted • However, in many cases (e.g., cancer treatment) both the length of life and the quality of life are different depending on the therapy selected • Sometimes the treatments that extend life the longest are also the most toxic, so a measure that incorporates both length of life and quality of life is needed in these cases Overview of CUA • Many health conditions … • Do not have an impact on patients’ length of life • However, do have an impact on patients’ QoL • CUA may be a good choice for comparing treatments for these conditions • e.g., hearing loss, seasonal allergies, and ED • CUAs are also useful when comparing treatments and outcomes that are very different • E.g., comparing the treatment of heart disease with prenatal care • Because outcomes for both treatments can be summarized into one common unit, such as QALYs Overview of CUA • When calculating QALYs … • 1 year of life in perfect health has a score of 1.0 QALY • If a person’s health is diminished by disease or treatment, 1 year of life in this state is valued at less than 1.0 QALY • By convention … • perfect health is assigned 1.0 per year • death is assigned 0.0 per year Graphical representation of QALYs • QALYs require 2 dimensions • Time (quantity of life) • Quality (value of that life or health state • QALYs = area of a rectangle (length • height) • One QALY: 1.0 0 1 2 time (years) Graphical representation of QALYs • But this is also equal to one QALY: 1.0 0.5 0 1 2 time (years) Simple Example • Consider the following patient experience: • lives 3½ years in perfect health (utility = 1.0) • then develops angina for 1 year (utility = 0.5) • then undergoes a CABG, allowing him to return to near-perfect health for 5 years (utility = 0.9) • then suffers a heart attack and lives for 6 months in relatively poor health (utility = 0.2) • and then dies. • How many life-years? • How many QALYs? Graphical description MI CABG Perfect Health 0.5 Post-MI Post-CABG angina Utility weight 1.0 0 1 2 3 4 5 6 7 8 9 10 Time in years QALYs = (3.5)(1.0) + (1)(0.5) + (5)(0.9) + (0.5)(0.2) = 8.6 So, the patient lived 10 years but received only 8.6 QALYs Steps in Calculating QALYs 1. Develop a description of each disease state or condition of interest 2. Choose the method for determining utilities 3. Choose subjects who will determine utilities 4. Multiply utilities by the length of life for each option to obtain QALYs Step 1: Develop Description of Each Disease State or Condition of Interest • The description should briefly depict the usual health effects expected from the disease state or condition • It should include … • • • • • the amount of pain or discomfort any restrictions on activities the time it may take for treatment possible changes in health perceptions (worry or concern) any mental changes Step 1: Develop Description of Each Disease State or Condition of Interest • Example: Description of hospital-based kidney dialysis: • You often feel tired and sluggish • A piece of tubing has been inserted into your arm or leg, which may restrict your movement • There is no severe pain but rather chronic discomfort • You must go to the hospital twice a week for 8 hours per visit • You must follow a strict diet (low salt, little meat, no alcohol) • Many people become depressed because of the irritations and restrictions, and some feel they are being kept alive by a machine Step 2: Choose Method for Determining Utilities Indirect assessment Health state classification systems Derived from multiattribute utility functions (MAUFs) Look like a QOL questionnaire EuroQOL (EQ-5D) Medical Outcomes Study 6-item short form (SF-6D) Direct assessment Rating scale Time tradeoff Standard gamble “Off the shelf” utility weights Beaver Dam study Catalog utility weights for many health states Published manuscripts Example: EuroQOL (EQ-5D) • An additive multiattribute utility function • 5 domains: • • • • • mobility self-care usual activities pain/discomfort anxiety/depression • For any given health state, indicate degree of limitation in each domain (none, some, extreme) “Indicate which statements best describe you current health in terms of…” 1. Mobility □ No problems walking about (1) □ Some problems walking about (2) □ Confined to bed (3) 2. Self-care □ No problems with self-care (1) □ Some problems washing or dressing himself/herself (2) □ Unable to wash or dress himself/herself (3) 3. Usual activities □ No problems with performing usual activities (e.g., work, study, housework, leisure activities) (1) □ Some problems with performing usual activities (2) □ Unable to perform usual activities (3) 4. Pain/discomfort □ No pain or discomfort (1) □ Moderate pain or discomfort (2) □ Extreme pain or discomfort (3) 5. Anxiety/depression □ Not anxious or depressed (1) □ Moderately anxious or depressed (2) □ Extremely anxious or depressed (3) Direct Methods for Determining Utilities Direct Methods for determining preference or utility scores Rating scale (RS) Standard gamble (SG) Time tradeoff (TTO) Direct Methods for Determining Utilities A disease state or condition or multiple disease states or conditions are described to subjects Subjects determine where these disease states or conditions fall between 0.0 (dead) and 1.0 (perfect health) Rating Scale (RS) • A line on a page with scaled markings somewhat like a thermometer with perfect health at the top (100) and death at bottom (0) Rating Scale (RS) • If patients place a disease state at 70 on the scale, the disease state is given a utility score of 0.7 • Mild seasonal allergies would not decrease a person’s QoL as much as being in stubborn pain for the year • Therefore, the preference score for … • mild allergies would be near the 1.0 mark • stubborn pain would be near 0 Visual Analog Scale (VAS) VAS is similar to the RS, but it does not have any markings between the best and worst scores, and subjects are told to mark an “X” some where between the two extremes to indicate their preferences Standard Gamble • Each subject is offered 2 alternatives • Alternative 1 is treatment with 2 possible outcomes: • return to normal health • immediate death • Alternative 2 is the certain outcome of a chronic disease state for life based on a person’s life expectancy • The probability (p) of normal health (vs. immediate death or 1-p) for alternative 1 is varied until the subject is indifferent between alternatives 1 & 2 (living with the disease state or condition) Standard Gamble Standard Gamble Example • A person considers 2 options: • a kidney transplant with • Alternative 1: • (p: 80% chance of returning to normal health ) • (1-p) 20% probability of dying during the operation • Alternative 2: certain dialysis for the rest of his/her life • If the person says he or she would have the operation if the chance of the successful operation p is 80% (chance of immediate death, 20%) … • The % chance of success is decreased until the person reaches his or her point of indifference (the point where the 2 options are nearly equal and the person cannot decide between the 2 outcomes) Standard Gamble Example • If the person says he or she would not have the operation if the % chance for success was 80% (chance of dying, 20%), the % chance of success is increased until the person reaches his or her point of indifference • Let us say that the first person chooses a 70% chance (p) of a successful operation (with a 30% chance [1-p] of immediate death) as the point of indifference between having a kidney transplant and living with kidney dialysis for life • The utility score for this person for this disease state or condition (kidney dialysis) would be calculated as the probability (p) of living a normal life after the operation, or 0.7 Time Tradeoff (TTO) • The subject is offered 2 alternatives • Alternative 1 is a certain disease state for a specific length of time (t), the life expectancy for a person with the disease, and then death • Alternative 2 is being healthy for time x, which is less than t Time Tradeoff (TTO) • Time x is varied until the respondent is indifferent between the 2 alternatives • The utility score for the health state is calculated as x divided by t Time Tradeoff (TTO) Example • A person with a life expectancy of 50 years is given 2 options: • Alternative 1 is being blind for 50 years • Alternative 2 is being healthy (including being able to see) for 25 years followed by death • If the person says he or she would rather be blind for 50 years than sighted for 25 years … • No. of years (x) of sight (healthy state) is increased until the person is indifferent between the two alternatives Time Tradeoff (TTO) • If the person would rather be sighted for 25 years than blind for 50 years, no. of years (x) of sight is decreased until the person is indifferent between the two alternatives • Let us say that for a person who expects to live 50 more years, the person’s point of indifference is 40 years of sight vs. 50 years of being blind • The utility score would be x/t = 40/50 or 0.8 Comparisons of the 3 Methods • RS advantage • • • • many disease states can be described to each subject can be conducted via a questionnaire without face-to-face interaction People are familiar with indicating preferences on these types of scales less cognitively demanding than the other 2 methods • RS disadvantage • do not incorporate time into the utility score as easily as the other 2 methods • may be biased in that people do not tend to cluster their values at the extreme ends of the scale but spread them throughout the range given, even if some health states are very similar in their values Comparisons of the Three Methods • SG advantage • “gold standard” and based on economic theory • SG disadvantage • more difficult for the participants • few disease states can be cured by an intervention that brings a person back to “normal health” • takes more resources than a self-administered questionnaire Comparisons of the 3 Methods • TTO advantages • more adaptable to diseases states than the SG • incorporates the time in the disease state more easily than the RS • TTO disadvantages • takes more resources than a self-administered questionnaire Comparisons of the 3 Methods • Unfortunately, the average utility scores for each disease state may differ depending on which method is used • RS scores have been shown to be consistently lower than either SG or TTO scores • TTO scores are sometimes lower than SG scores • Some work has been done on creating algorithms that transform scores from one method to approximate scores collected from another method • Interactive computer software is being developed to decrease the need for face-to-face questioning for the SG method Step 3: Choose Subjects Who Will Determine Utilities Who should determine utilities? patient with the disease? health care professional? caregiver? people from the general population? Step 3: Choose Subjects Who Will Determine Utilities • Patients may understand the effects of the disease better than the general public • Should the parent or caregiver substitute for the patient? (young child or person with dementia) • Health care professionals could provide good estimates because they understand various diseases • However, HC professionals may not rate discomfort and disability as seriously as patients or general public Step 3: Choose Subjects Who Will Determine Utilities • Based on economic theory, the viewpoint of the analysis should be that of society, so the utility scores should be determined by the general population (society) • However, they may not be familiar with the complex outcomes associated with each disease state or outcome Step 3: Choose Subjects Who Will Determine Utilities • In many cases, a patient with the specific disease state or condition gives higher utility scores than others • This may be because of the patient’s adapting or adjusting to the disease state or condition • In the literature, health care professionals are often used to determine utility scores • Because these professionals have had experience with the disease states and are easily accessible for interviews Step 4: Multiply Utilities By The Length of Life for Each Option to Obtain QALYs • When comparing the options, the difference in the length of life permitted by each option is multiplied by the utility scores obtained • In the following table, it is assumed that the utility score for each year of additional life is constant • If a CEA, which option would be cost effective? • If the quality of those years is incorporated into the equation by calculating QALYs, option A becomes dominant in that it costs less and provides a better outcome (more QALYs) Step 4: Multiply Utilities By The Length of Life for Each Option to Obtain QALYs Summary • CUA has the advantage of using one outcome measure (usually QALYs) to incorporate various morbidity -and mortality-related health outcomes • Utility measurement is not regarded as being as precise or “scientific” as natural health unit measurements (e.g., BP, years of life) used in CEAs • Utility measures have been criticized for not being sensitive to small, but clinically meaningful, changes in health status • There is no consensus on which type of instrument to use (RS, SG, or TTO) Summary • There is no consensus on which group of people (e.g., patients, care-givers, or the general population) to interview to determine utility scores • Different results are obtained depending on which instrument and which group is chosen • As with CEA, an incremental cost-utility ratio can estimate the added costs for the added benefit of a treatment • But, as with CEA, it does not quantify if the added cost is worth paying for the added benefit • In other words, what is a QALY worth?

Cost-Utility Analysis

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