# Presentation: 175670

## 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 K
- Centers for Disease Control and Prevention (CDC)

**Notes:**
As the title suggests, the model here looks at a situation in which the management of CT and GC are not delineated from each other

## 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?

**Notes:**
For clinics operating on fixed budgets
At what parameter levels is it cost effective to include or exclude GC in a CT screening program and vice versa?
 Amplified tests vrs. Non-amplified tests

## Clinical Management Decision

**Clinical Management Decision**

**Notes:**
Dual treatment: Treat for one lab-confirmed pathogen and presumptively treat for the other pathogen, treat for 2 lab-confirmed infections

## Clinical Alternatives Considered

- Screen and treat for CT only
- Screen and treat for GC only
- Screen and treat for both CT and GC
- Screen and treat for CT only and presumptively treat for GC
- Screen for and treat for GC only and presumptively treat for CT

- For each risk-group the following strategies are possible:

**Notes:**
4) Although it may not be a desirable strategy we still considered it because the outcomes is equivalent to that effected by using Azithromycin to treat

## 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

**Notes:**
Better outcomes may be realized by violating if uniform test and treatment condition. In fact non-uniform tests are be used in some places

## 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 Ratesby 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

**Notes:**
Baseline values

## Variables - Test

| CT | Test | Sensitivity | Specificity | Cost |
| --- | --- | --- | --- | --- |
| 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 | 7.82 |

- BDPT – 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

## 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 | #Cured | Cost-saving† |
| --- | --- | --- | --- | --- |
| 17,437 | CT (all)GC (all) | BDPT-DualBDPT-Dual | 53.3 | -1,391 |
| 15,635 | CT (all)GC (all) | BDPT-CTculture | 52.6 | 192 |
| 14,214  | CT (all)GC ( 24, pres.) | Pace 2CTculture | 51.9 | 1,432 |
| 11,458 | CT (all)GC (none) | BDPT-CT- | 49.6 | 3,483 |
| 7,668 | CT ( 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

**Notes:**
Cohort of 1000 asymptomatic women 	- PID (68)
Cost and outcomes must be carefully examined when a switch from one test to a more sensitive is being considered
Although presumptive treatment of GC is not preferred because of drug resistance issues, the strategy is still included because about the same number of GC interventions would occur when Azithromycin is the chosen treatment regimen
Cost-benefit when universal screening is done with Pace 2C is comparative to the strategy above: $7569, 44, $5906.

## Results – FP Clinic

| Total Program Cost† | Screening Coverage | Test | #Cured | Cost-saving† |
| --- | --- | --- | --- | --- |
| 17,437 | CT (all)GC (all) | BDPT-DualBDPT-Dual | 53.3 | -1,391 |
| 15,635 | CT (all)GC (all) | BDPT-CTculture | 52.6 | 192 |
| 14,214  | CT (all)GC ( 24, pres.) | Pace 2CTculture | 51.9 | 1,432 |
| 11,458 | CT (all)GC (none) | BDPT-CT- | 49.6 | 3,483 |
| 7,668 | CT ( 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

**Notes:**
Cohort of 1000 asymptomatic women 	- PID (68)
Cost and outcomes must be carefully examined when a switch from one test to a more sensitive is being considered
Although presumptive treatment of GC is not preferred because of drug resistance issues, the strategy is still included because about the same number of GC interventions would occur when Azithromycin is the chosen treatment regimen
Cost-benefit when universal screening is done with Pace 2C is comparative to the strategy above: $7569, 44, $5906.

## Results – FP Clinic

| Total Program Cost† | Screening Coverage | Test | #Cured | Cost-saving† |
| --- | --- | --- | --- | --- |
| 17,437 | CT (all)GC (all) | BDPT-DualBDPT-Dual | 53.3 | -1,391 |
| 15,635 | CT (all)GC (all) | BDPT-CTculture | 52.6 | 192 |
| 14,214  | CT (all)GC ( 24, pres.) | Pace 2CTculture | 51.9 | 1,432 |
| 11,458 | CT (all)GC (none) | BDPT-CT- | 49.6 | 3,483 |
| 7,668 | CT ( 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

**Notes:**
Cohort of 1000 asymptomatic women 	- PID (68)
Cost and outcomes must be carefully examined when a switch from one test to a more sensitive is being considered
Although presumptive treatment of GC is not preferred because of drug resistance issues, the strategy is still included because about the same number of GC interventions would occur when Azithromycin is the chosen treatment regimen
Cost-benefit when universal screening is done with Pace 2C is comparative to the strategy above: $7569, 44, $5906.

## Results – STD Clinic

| Total Program Cost† | Screening Coverage | Test | #Cured | Cost-saving† |
| --- | --- | --- | --- | --- |
| 18,878 | CT (all)GC (all) | BDPT-DualBDPT-Dual | 97.8 | 10,578 |
| 16,928 | CT (all)GC (all) | BDPT-DualCulture | 92.8 | 11,020 |
| 12,788 | CT ( 20)GC ( 20) | BDPT-DualBDPT-Dual | 85.4 | 12,934 |
| 12,757 | CT ( 20, pres.)GC (all) | BDPT-CTCulture | 83.0 | 12,245 |
| 8,331 | CT (all)GC (all) | Pace 2CPace 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

## Results – STD Clinic

| Total Program Cost† | Screening Coverage | Test | #Cured | Cost-saving† |
| --- | --- | --- | --- | --- |
| 18,878 | CT (all)GC (all) | BDPT-DualBDPT-Dual | 97.8 | 10,578 |
| 16,928 | CT (all)GC (all) | BDPT-DualCulture | 92.8 | 11,020 |
| 12,788 | CT ( 20)GC ( 20) | BDPT-DualBDPT-Dual | 85.4 | 12,934 |
| 12,757 | CT ( 20, pres.)GC (all) | BDPT-CTCulture | 83.0 | 12,245 |
| 8,331 | CT (all)GC (all) | Pace 2CPace 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

## Results – STD Clinic

| Total Program Cost† | Screening Coverage | Test | #Cured | Cost-saving† |
| --- | --- | --- | --- | --- |
| 18,878 | CT (all)GC (all) | BDPT-DualBDPT-Dual | 97.8 | 10,578 |
| 16,928 | CT (all)GC (all) | BDPT-DualCulture | 92.8 | 11,020 |
| 12,788 | CT ( 20)GC ( 20) | BDPT-DualBDPT-Dual | 85.4 | 12,934 |
| 12,757 | CT ( 20, pres.)GC (all) | BDPT-CTCulture | 83.0 | 12,245 |
| 8,331 | CT (all)GC (all) | Pace 2CPace 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

**Notes:**
2) Conversely, screen and treat for GC, and screen GC-positives for CT
3) Threshold prevalence values for positive cost benefits is very sensitive to PID cost

## 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

**Notes:**
It may be used, among other things, as an evaluation tool for screening programs - providing support for advocacy for additional funding, or otherwise, through the demonstration of screening outcomes of different strategies.