a unified optimal resource allocation model for screening and treating asymptomatic women for...

A Unified Optimal Resource Allocation Model for Screening and Treating

Asymptomatic Women for Chlamydia Trachomatis and Neisseria Gonorrhoeae

Abban B, Tao G, Gift T, Irwin KCenters for Disease Control and Prevention

(CDC)

Background

Up to 70% CT and up to 50% GC infections are asymptomatic

CT infection among GC infected populations can be as high 50%

Different segments of the population have different prevalences of CT, GC, and co-infection; range of disparities is wide

Availability of different testing technologies at varying cost and performance

Many clinics operate under fixed budgets and cannot accommodate universal screening

Study Objective

Determines the optimal combination of screening coverage, test selection and treatment for CT and GC in asymptomatic women; specifically

At what prevalence is it cost-saving to screen a population for CT or GC?

Is it more beneficial to screen with more sensitive but more expensive tests?

Is presumptive treatment cost-saving?

What test(s) should be used?

Which risk-group(s) should be screened for CT, or GC, or both?

Should patient be dual-treated?

What treatment(s) should be used?

Clinical Management Decision

Clinical Alternatives Considered

1. Screen and treat for CT only2. Screen and treat for GC only 3. Screen and treat for both CT and GC 4. Screen and treat for CT only and

presumptively treat for GC5. Screen for and treat for GC only and

presumptively treat for CT

For each risk-group the following strategies are possible:

Methods

The optimal strategy was defined as one that maximized the number of women cured or the cost-saving value (cost of averted PID minus

screening and treatment costs for CT and/or GC) Selective screening based on readily

ascertained risk-factor: Age 4 tests each for CT and GC, including dual

test(s) 2 treatment regimens for CT and 3 for GC A mixed integer optimization model for a

hypothetical cohort of 1000 asymptomatic women

Model Assumptions

All women who visited the clinic lacked symptoms of CT and GC infections

A strategy could allow the screening of selected age groups or all patients

Return rate for treatment was assumed to be the same for all age groups

Test and treatment for each infection were the same all age groups

Variables

CT and GC positivity by age group

Co-infection rates by age group

Tests sensitivity, specificity and cost

Treatments effectiveness and cost

All parameter values were from

published literature

Test Positivity Ratesby Clinic Type

Age group(years)

CT(%)

GC(%)

GC with CT (%)

15 – 19 10.6 1.2 46.0

20 – 24 6.9 0.8 39.3

25 2.3 0.4 30.0

Age group(years)

CT(%)

GC(%)

GC with CT (%)

15 – 19 12.5 8.1 45.5

20 – 24 8.0 6.5 32.7

25 3.0 2.0 20.0

STD clinic

Family planning clinic

Variables - TestCT Test Sensitivi

tySpecifici

tyCost

1 Pace CT 0.780 0.780 8.03

2 BDPT-CT 0.993 0.993 9.42

3 Pace 2C 0.928 0.928 5.61

4 BDPT-Dual

0.981 0.981 7.82

GC

1 Culture 0.850 0.995 4.20

2 PCR 0.995 0.990 9.26

3 Pace 2C PCR 0.993 5.61

4 BDPT-Dual 0.900 0.995 7.82BDPT – Becton Dickinson Probe Tec

Variables - Treatment

CT Treatment Effectiveness

Cost

1 Doxycycline 0.900 4.00

2 Azithromycin

0.965 9.50

GC

1 Ceftriaxone 0.977 15.37

2 Ciprofloxacin

0.972 5.27

3 Cefpodoxime

0.965 7.32

Clinical Costs and Outcomes

Other CostsPatient visitPID case

ProbabilitiesReturn rate for treatmentPID in untreated cases 0.21

1,434.00$ 14.00$

0.80

Results

Test Positivity at which Screening is Cost-saving

PID cost(US $)

Pathogen (Test type)

CT(Pace 2)

GC(Culture)

GC(PCR)

1434 5.1% 2.4% 4.9%

1900 3.7% 1.8% 3.6%

4131 1.7% 0.8% 1.6%

Sensitive to PID cost

Results – FP Clinic

Total Program Cost†

Screening Coverage

Test #CuredCost-

saving†

17,437

CT (all)GC (all)

BDPT-Dual

BDPT-Dual

53.3 -1,391

15,635CT (all)GC (all)

BDPT-CTculture

52.6 192

14,214 CT (all)GC ( 24, pres.)

Pace 2CTculture

51.9 1,432

11,458CT (all)GC (none)

BDPT-CT-

49.6 3,483

7,668CT ( 24)GC (pres.)

BDPT-CT-

43.8 5,229‡

CT (2.3 - 10.6%), GC (0.4 - 1.2%), GC with CT (30.0 - 46.0%)

† All costs in US dollars (2003) | BDPT – Becton Dickinson Probe Tec‡ Optimal cost-saving strategy | pres. – presumptively treat

Results – STD Clinic

Total Program Cost†

Screening Coverage

Test#Cure

dCost-

saving†

18,878

CT (all)GC (all)

BDPT-Dual

BDPT-Dual

97.8 10,578


BDPT-Dual

Culture92.8 11,020

12,788

CT ( 20)GC ( 20)

BDPT-Dual

BDPT-Dual

85.4 12,934

12,757CT ( 20, pres.)GC (all)

BDPT-CTCulture 83.0 12,245


Pace 2CPace 2C

82.0 15,849‡

CT (3.0 – 12.5%), GC (2.0 – 8.1%), GC with CT (20.0 – 45.5%)

† All costs in US dollars (2003) | BDPT – Becton Dickinson Probe Tec‡ Optimal cost-saving strategy | pres. – presumptively treat

Limitations

The alternative of screening and treating for CT and screening CT-positives for GC was not considered

Published range of values for direct cost attributable to PID is wide: (1,433 – 5,000)

Repeat infections were not considered CT and GC positivity in asymptomatic

STD clinic patients may be less than the reported population-wide rates

Conclusions

Optimal control strategy varies with CT and GC positivity, CT-GC co-infection rates, total program budget, test costs and PID cost

Influence of treatment cost on overall program cost is minimal

A switch from one test to another may not yield significant change in the number of women cured

The optimal strategy from a cost-saving perspective and from a number-of-cures perspective may vary

The model provides a flexible tool to analyze different scenarios when identifying a control strategy for CT, GC, or both

a unified optimal resource allocation model for screening and treating asymptomatic women for...

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