raanan shamir, md cost effectiveness of population screening 15.9.2010
TRANSCRIPT
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Raanan Shamir, MD
Cost Effectiveness of Population Screening
15.9.2010
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Screening-WHO Definition
An investigation whereby:
a simple test is applied to
an asymptomatic population without consulting a health care
system in order to identify a disease.
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Mass screening
Celiac disease fulfils all requirements for a mass screening program: It is common Specific screening tests are
available Definite treatment (gluten-free
diet) is available If unrecognized, morbidity and
complications may ensue.
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However… Most available data about the
epidemiology of CD is derived from studies in symptomatic patients
GFD is not easy to maintain and may constitute a cumbersome lifestyle
There is a paucity of data on the cost–effectiveness (CE) of CD screening
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On GFD IgA and IgG TTG decreased significantly over 12 months
About 25% admitted sub optimal compliance on social occasions explaining the continuing (although low) positivity in 8/28 subjects after 18 months
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Prevalence of CD is high in Italian schoolchildren.
2/3 of cases were asymptomatic. Acceptance of the program was
good, as was dietary compliance. Given the high prevalence and
possible complications of untreated CD, mass screening deserves careful consideration.
Tommasini A, et al. Arch Dis Child 2004
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Med Desc Making 2006;26:1-12
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Methods
We developed a state-transition Markov model, from a societal perspective, to evaluate whether it is cost effective to screen the entire population at the age of 18 years (range 6-30 years), for CD.
Since the model uses values that can vary between studies and countries, the influence of establishing a certain value on the model was examined using the sensitivity analysis (examining the model within the range of preset values).
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Markov Model for CD Screening
Unknown CD
No CD
Known CD no GFD
Known CD Strict
diet
Dead
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Methods (Cont.)
Effectiveness was measured by life expectancy in each strategy (TTG, EMA, IgA and AGA IgA combinations).
We calculated the incremental average cost-effectiveness (CE) ratio for each strategy (additional expected cost divided by additional expected effectiveness) compared with the next least expensive strategy.
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Costs
We considered only direct health care costs, representing the average payments for each coded procedure based on the 2004 Medicare Fee Schedule (http://www.hgsa.com/professionals/feedb-2004.shtml)
The cost of biopsy includes additional average costs of endoscopy and its complications (bleeding, perforations, death)
The costs of evaluation of symptoms include the following: Physician’s visits, laboratory tests (two physicians visits, complete blood count, chemistry panel, CD serology), and endoscopy that is mandatory for the diagnosis of CD
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Cost values in $
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Results
• All screening strategies resulted in life year saving and reductions in mortality related to CD
• Base-case analysis at an annual discount rate of 3% revealed a US$ 49,491 per life-year gained for screening compared to no screening using the EMA strategy
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ICER as a function of prevalence
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ICER as a function of SMR in CD
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Conclusions (1)
Mass screening would be CE in populations with a high prevalence of CD, over a wide range of ages at screening, assuming that the mortality rate is higher in undiagnosed CD, and that implementing and adhering to a GFD in cases diagnosed by screening reduces the mortality rate
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Conclusions (2)
From a CE perspective, EMA is the best serological marker for mass screening for CD
Due to the uncertainties regarding the validity of our assumptions, screening for CD would be justified only if these assumptions are proved to be correct
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To determine the CE of mass screening within the young adult population for CD
To document the changes in quality of life produced by CD screening
To define the parameters constituting the highest impact on the CE
T. Hershcovici1 M. Leshno, E. Goldin, E. Israeli & R. Shamir. Aliment Pharmacol Ther 2010;31:901-10
Mass screening, the 2010 Update
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METHODS
Design: State transition Markov model
Perspective: Third-party payer Interventions: CD screening compared
to a no-screening strategy Outcome Measures:
Quality Adjusted Life Years (QALYs) Incremental Cost-Effectiveness Rate (ICER)
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Positive Serology
IBS
IDA
Morbidity
Mortality
QALYs
SMR
Latent Silent Overt
%over time
Screening
GFD QALYs
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Strategy
Cost
(US$) QALYsICER
(US$/QALYs)
No
Screening 24.94 26.9031
Screening 158.64 26.9057* 48.960
* The screening strategy resulted in a gain of 0.0027 QALYs.
Results
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Parameters with Significant Influence on ICER
Time delay to CD diagnosis
Utility of CD patients adhering to GFD
Prevalence of CD
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Screening would be CE if the time delay to diagnosis is longer than 6 years, and utility of
GFD adherence is greater than 0.978.
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Two-Way Sensitivity Analysis
Screening is not CE for a time delay less than 3.5 years independent from CD prevalence*
Screening is not CE for a time delay less than 5.2 years independent from the utility of adherence to GFD*
*ICER=50,000US$/QALY
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Our model suggests that mass screening for CD of the young-adult general population is associated with improved QALYs and is a cost effectiveness strategy However:
Shortening of the time delay to diagnosis by heightened awareness of
health-care professionals may be a valid alternative to screening
Conclusions
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Base-case values and ranges used in sensitivity analysis
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Parameters that do not Influence ICER Significantly
Adherence to GFD
Probability to suffer of IDA or IBS-like symptoms
The utility of IDA or IBS-like symptoms
Cost of endoscopic biopsy and of serologic testing
Standardized Mortality Rate
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Screening for Celiac Disease-Justified?
CD is the most common food-based disease
Clinically based early diagnosis is difficult and is frequently delayed**
There are diagnostic serologic tests that are both specific and sensitive and can be applied
to a large population**
Undiagnosed patients remain at risk for complications
A gluten-free diet (GFD) relieves symptoms and decreases morbidity and mortality
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Perform CD screening in high-risk conditions
associated with increased prevalence of
disease
Mass-screening for CD remains controversial
CD Screening-Recommendations
Gastroenterology 2005;128:S104
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Markov Model – No-Screening Arm
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Markov Model–Screening Arm
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MortalitySMR
No Screening
IBS
IDA
Morbidity
QALYs Celiac Disease
GFD
Latent Silent Overt
Percentage over time
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Base–Case Analysis:Estimation of Parameters
Prevalence of CD in the general population: 1%
Standardized Mortality Rate (SMR):Untreated CD patients: 1.6
CD patients on GFD: 1.1
Average time delay to CD diagnosis from onset of symptoms: 6 years
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Base–Case Analysis:Estimation of Parameters
Compliance to GFD:Symptomatic CD patients: 82% at 10 years
Asymptomatic CD patients: 60% at 10 years
Utility of GFD: 0.98
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Base–Case Analysis:Estimation of Parameters
•Sensitivity of IgA anti-tTG : 95%
•Specificity IgA anti-tTG :98%
•Sensitivity of IgG anti-tTG* :98.7%
•Specificity IgG anti-tTG* :98.6%
*in IgA deficient patient
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Base–Case Analysis:Estimation of Parameters
Annual probability to develop symptoms in asymptomatic CD patient:2.8%
Prevalence of symptoms in CD patients:IBS-like symptoms: 30%
Iron-deficiency anemia: 50%
Utility of symptoms: IBS-like symptoms: 0.73
Iron-deficiency anemia: 0.76
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Sensitivity Analysis on Prevalence of CD
Screening remained cost-effective for a CD prevalence range between 0.875-2%.
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Sensitivity Analysis on Time Delay to CD diagnosis
For a time delay of less than 5.9 years, screening for CD is not cost-effective.
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Sensitivity Analysis on Utility of Adherence to GFD
For utility of adherence to GFD between 0.95-0.978, screening for CD is not cost-effective .
For an estimated utility less than 0.95, the no-screening strategy becomes dominant.
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Sensitivity Analysis on SMR
A SMR between 1.2-2.7 for symptomatic CD patients had no major effect on ICER.
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•Developed a case-finding strategy based on testing for TTG IgA antibodies in subjects showing
predefined signs and symptoms or belonging to at-risk groups .
•69 primary care doctors and 60 primary care paediatricians agreed to participate .
•1041 adults and 447 children were selected for TTG-Ab testing during the year of the study
(2001).
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Berti I, et al. Case-finding startegy, 2006
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Berti I, et al. Case-finding startegy, 2006
•31 subjects (2.08%, 19 adults and 12 children) were ultimately diagnosed as CD, while no cases of coeliac
disease had been diagnosed by the participating doctors in the previous year, 29 subjects were diagnosed as
coeliacs in the year after the completion of the study (2002) .
•The prevalence of confirmed CD in the population under study increased from 1:1506 to 1:1073 in adults and
from 1:827 to 1:687 in children from year 2000 to 2001. When cases diagnosed in 2002 are included, the
prevalence is 1:832 and 1:602, respectively .
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Berti I, et al. Case-finding startegy, 2006Conclusions
•Case-finding is a feasible and successful strategy for detecting undiagnosed CD patients and has
the important added value of increasing the awareness of the disease among primary care
physicians• It represents a cost-effective alternative to
population screening for reducing the burden of undiagnosed CD