Cost effectiveness of rapid HIV and syphilis testing algorithms in antenatal care

Claire C. Bristow, MScFielding School of Public Health

University of California, Los Angeles

Satellite Session Sunday July 20th, 2014

Dualelimination.org

What is a cost-effectiveness study?

• Economic analysis that compares relative costs and outcomes – In this case we’re looking rapid point-of-care HIV

and syphilis testing algorithms

Why do we do cost-effectiveness studies?

• The concept of cost effectiveness is applied to resource allocation and management activities

– Getting the most “bang for your buck” – Spending the least to gain the most– Using evidence to determine how to prioritize

resources: “evidence-based public health”

Goals

1. To measure adverse pregnancy outcomes associated with alternative testing strategies

2. To measure the monetary costs of alternative testing strategies

3. To develop a cost-effectiveness model for policy-makers and implementers to determine the most cost-effective dual elimination strategy

• We used Malawi as the base case for this analysis

• Option B+ start lifelong highly-active antiretroviral therapy at 14 weeks of gestation

5 Testing Algorithms

Dual rapid test for HIV and syphilis

• 1 single rapid test for HIV• 1 single rapid test for syphilis

• HIV rapid test • Lab-based TPPA/RPR for syphilis

HIV rapid test only

No Testing

Simulation Model• 100,000 pregnant women in

Malawi• Followed through decision tree

(testing pathway) and treatment, each step governed by probabilities

• Key inputs from data out of Malawi

• TreeAge Pro Software (Williamstown MA, USA)

Simulation Model

• Estimated expected adverse pregnancy outcomes based on each testing strategy– HIV mother-to-child transmission (MTCT)– Newborn syphilis infection– Prematurity/low birth weight– Neonatal death– Stillbirth

Decision Tree – Simulation model

• A schematic tree-shaped diagram used to show a statistical probability

• Each branch of the decision tree represents a possible event

• The tree structure shows how one choice or event leads to the next, and the use of branches indicates that each option is mutually exclusive

Decision tree - No testing

No testing

Proportion HIV uninfected

Proportion of HIV uninfected women

who are syphilis uninfected

Proportion of these women with adverse pregnancy outcome

Proportion of HIV uninfected women

who are syphilis infected

Proportion of these women with adverse pregnancy outcome

Proportion HIV infected

Proportion of HIV infected women who

are syphilis uninfected

Proportion of these women with adverse pregnancy outcome

Proportion of HIV infected women who are syphilis infected

Proportion of these women with adverse pregnancy outcome

.106

.9891

.0109.894

.978

.022

One branch of the HIV rapid test only decision tree

HIV rapid test algorithm

Proportion of women receiving

HIV rapid test

HIV infected

HIV test positive (test sensitivity)

HIV treatment received

Syphilis infected Pregnancy outcome

Syphilis uninfected

Pregnancy outcome

HIV treatment LTFU …

HIV test negative …

HIV uninfected …

Not tested …

COST EFFECTIVENESS ANALYSIS

Costs• We considered costs of testing incurred by

both the health system and the woman (labor costs determined using standard WHO health worker salaries for the region, patient travel costs, and test costs, etc.)

• We included costs of treatment for both syphilis and HIV infection in the pregnant woman and infant

• All costs were converted to 2012 US Dollars.

Effectiveness: Disability adjusted life years (DALYs)

• The disability adjusted life years (DALYs) is a measure of overall disease burden, expressed as the number of years lost due to ill-health, disability or early death

• DALYs were calculated using disability weights from the Global Burden of Disease study1

• A disability weight is a weight factor that reflects the severity of the disease on a scale from 0 (perfect health) to 1 (equivalent to death)

• DALYs were adjusted for co-infection2

1. Lopez et al 20062. Owusu-Edusei et al 2014

DALYs• The DALY metric is used to provide a single number

to capture the health impact caused by a illness

• A DALY of 1 could represent 1 year of life lost (due to early death), 1.7 years spent with blindness, 5.2 episodes of malaria, etc.

• Syphilis infection in the infant has a disability weight of 0.315 per year and is estimated to last for 3 years. So a child born with congenital syphilis would receive a lifetime DALY value of 0.945

Incremental cost effectiveness ratio

• Cost-effectiveness is typically expressed as an incremental cost effectiveness ratio (ICER), the ratio of change in costs to the change in effects

ICER =

Key inputs: epidemiology

Cohort• 10.6% HIV prevalence among pregnant

women1 – 24.8% of those with AIDS2

• 1.09% syphilis prevalence among HIV-uninfected1

• 2.2% syphilis prevalence among HIV-infected1

1. Malawi Government 20122. Mwapasa 2006

Key inputs

Test accuracy • Sensitivity and specificity estimates were

determined from literature review of field studies

Key inputs: Health system structure and use

Treatment • Option B+ for treatment of HIV infection• Treatment for maternal syphilis infection with

one injection (2.4 MU Benzathine Penicillin)

Key inputs: Costs

Screening test costs• $0.80 Single HIV rapid test• $0.55 Single Syphilis rapid test• $2.39 Syphilis laboratory tests (RPR/TPPA)1

• $1.30 Dual Rapid test – SD Duo®

Patient costs• Treatment costs for syphilis or HIV infection for life

of infant • Pregnancy outcome costs1. Owusu-Edusei 2011

RESULTS

Expected adverse pregnancy outcomes per 100,000 pregnancies

No testing program 17,127 adverse outcomes

HIV rapid testing only 15,820 adverse outcomes

HIV rapid testing and laboratory-based syphilis testing

15,779 adverse outcomes

1 single HIV and 1 single syphilis rapid testing

15,775 adverse outcomes

Dual HIV/syphilis testing 15,370 adverse outcomes

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

186 186 174 173 51

4852 4852 4836 4834 4669

3112 3112 3105 3104 3031

6370 6370 6365 6365 6319

2607 1300 1299 1299 1300 HIV MTCT

Prematurity/ Low Birth Weight

Neonatal Death

Still Birth or Fetal Loss

Syphilis Infec-tion in Infant

Num

ber

of A

dver

se P

regn

ancy

Out

com

es

Summary results from the cohort decision model comparing the expected effects (DALYs) of the pregnancy and costs (2012 U.S. Dollars) for all 5 antenatal HIV and syphilis testing algorithms and a no-testing strategy in the Malawi setting.

Total Program and Outcome

Costs

No testing$20,783,454

Dual HIV/syphilis$21,274,678

HIV test only$21,583,611

Single rapid tests for HIV & syphilis $21,593,145

HIV rapid test & RPR/TPPA for syphilis $21,605,356

Summary results from the cohort decision model comparing the expected effects (DALYs) of the pregnancy and costs (2012 U.S. Dollars) for all 5 antenatal HIV and syphilis testing algorithms and a no-testing strategy in the Malawi setting.

Total Program and

Outcome Costs

DALYs

No testing$20,783,454 269,400

Dual HIV/syphilis$21,274,678 228,829

HIV test only$21,583,611 235,716

Single rapid tests for HIV & syphilis $21,593,145 235,023

HIV rapid test & RPR/TPPA for syphilis $21,605,356 235,094

Summary results from the cohort decision model comparing the expected effects (DALYs) of the pregnancy and costs (2012 U.S. Dollars) for all 5 antenatal HIV and syphilis testing algorithms and a no-testing strategy in the Malawi setting.

Total Program and

Outcome Costs

Cost increase from no testing

DALYS

No testing$20,783,454

-269,400

Dual HIV/syphilis$21,274,678 $491,224 228,829

HIV test only$21,583,611 $800,158 235,716

Single rapid tests for HIV & syphilis $21,593,145 $809,692 235,023

HIV rapid test & RPR/TPPA for syphilis $21,605,356 $821,902 235,094

Summary results from the cohort decision model comparing the expected effects (DALYs) of the pregnancy and costs (2012 U.S. Dollars) for all 5 antenatal HIV and syphilis testing algorithms and a no-testing strategy in the Malawi setting.

Total Program and outcome

Costs

Cost increase from no testing

DALYS DALYs prevented compared

to no testing

No testing$20,783,454

-269,400 -

Dual HIV/syphilis$21,274,678 $491,224 228,829 40,571

HIV test only $21,583,611 $800,158 235,716 33,684

Single rapid tests for HIV & syphilis $21,593,145 $809,692 235,023 34,377

HIV rapid test & RPR/TPPA for syphilis $21,605,356 $821,902 235,094 34,306

Summary results from the cohort decision model comparing the expected effects (DALYs) of the pregnancy and costs (2012 U.S. Dollars) for all 5 antenatal HIV and syphilis testing algorithms and a no-testing strategy in the Malawi setting.

Total Program and outcome

Costs

Cost increase from no testing

DALYS DALYs prevented compared

to no testing

ICER*

No testing $20,783,454 - 269,400 - -

Dual HIV/syphilis $21,274,678 $491,224 228,829 40,571 12.11HIV test only $21,583,611 $800,158 235,716 33,684 Strictly

dominatedSingle rapid tests for

HIV & syphilis $21,593,145 $809,692 235,023 34,377Strictly

dominated

HIV rapid test & RPR/TPPA for syphilis $21,605,356 $821,902 235,094 34,306

Strictly dominated

*Incremental cost effectiveness ratio (ICER) is the ratio of the change in costs to incremental benefit of an algorithm.

Conclusions

• A dual HIV/syphilis testing algorithm in antenatal care would be the most effective means to reduce the number of adverse outcomes of pregnancy

• The dual point-of-care testing algorithm had lower overall costs and decreased life-time disability when compared to the other testing choices

Limitations

• Did not include procurement costs for tests or training costs

• Inputs are based on estimates from a variety of studies, actual measures may change over time

• This is a purely economic perspective, this doesn’t include the intangible values society places on pregnancy outcomes

Conclusions

• Integrating the screening of syphilis into antenatal HIV prevention programs through dual rapid point-of-care testing would increase the number of maternal infections detected and have the greatest impact on the prevention of HIV and syphilis related adverse pregnancy outcomes

Next steps, sensitivity analyses

Visit our posters!

• "Cost-effectiveness of dual HIV and syphilis testing“ - Thursday, 24 July 2014 from 12:30 - 14:30, Exhibition Hall, Ground Level THPE416

• “Field evaluation of a dual rapid diagnostic test for HIV and syphilis in Lima Peru using SD BIOLINE HIV/Syphilis Duo“ - Wednesday, 23 July 2014 from 12:30 - 14:30, Exhibition Hall, Ground Level WEPE050

Acknowledgements

• Jeffrey Klausner, UCLA• Elysia Larson, Harvard

• Thomas Gift, CDC• Kwame Owusu-Edusei, CDC• Lori Newman, WHO• Fern Terris-Prestholt, LSHTM• Peter Vickerman, Bristol University

THANK YOU

Please get in touch if you want more information or have comments.

ccbristow@ucla.edu

Dualelimination.org