David P. Wilson

Sally M. Blower

Presented by Harry Chang

April 7th, 2010

2 Biomathematicians: UCLA AIDS Institute

Topic: Equitable distribution of ARV in resource-constrained countries

Proposal: Mathematical model for achieving OEAS

Focus: KwaZulu-Natal province of South Africa

ARV Allocation DecisionBackgroundExperimental OutlineMethodsResultsBest StrategyFuture ExtensionsAuthors’ Conclusions

Caveats & Shortcomings

Discussed extensively: ARV for HIV/AIDS

Last presentation: ending note

Novel scientific approach

Interesting proposed resolution

ARV therapy expensive: barriers to providing essential medicines (eg. patents protecting IP), long-term treatment etc.

Cannot afford to treat all afflicted individuals

How to make decision?

EpidemiologyPreferential:

MenPregnant womenChildrenSickestHighest efficiencyMilitaryDominant ethnic group…

LotteryPeris, S.J. On a never-ending waiting list: toward equitable access to anti-retroviral treatment? Experiences from Zambia .

Health and Human Rights, 8, 76-102.

McGough LJ, Reynolds SJ, Quinn TC & Zenilman JM. Which patients first? Setting priorities for antiretroviral therapy where resources are limited. Am J Pub Heal, 95, 11173-1181.

1) All similar cases be treated alike

2) Utilitarian: maximize overall social benefits

3) Egalitarian: Equal distribution to different groups

4) Maximin: Prioritize least advantaged individuals

Ethical: Equality“Each individual with HIV has an equal chance

of receiving ARV”

Intention: mathematical model of treatment accessibility & equity objective function OEAS

South Africa epidemic (12% of population)

KwaZulu-Natal = largest province

Population: 9.4 million

highest HIV-positive (21% of all South Africa)

Total HCF: 54

Photo source:

Wilson DP, Blower SM (2005) Designing equitable antiretroviral allocation strategies in resource-constrained countries. PLOS Medicine. DOI: 10.1371/journal.pmed.0020050

April 2004

17 HCF in KwaZulu-Natal for ARV Roll-out

Variable distance between communities & HCFSpatial distribution diverse heterogeneity,

unequal accessibility to ARV

Photo source: Wilson DP, Blower SM (2005) Designing equitable antiretroviral allocation strategies in resource-constrained countries. PLOS Medicine. DOI: 10.1371/journal.pmed.0020050

Photo source:

Wilson DP, Blower SM (2005) Designing equitable antiretroviral allocation strategies in resource-constrained countries. PLOS Medicine. DOI: 10.1371/journal.pmed.0020050

Intention: Determine ARV OEAS for KwaZulu-Natal

Examine parameters 1) Changing catchment region of HCF

20km OR 40km OR 60km2) Number of HCF

1 OR 17 OR 54

Compare to1) All ARV to Durban2) Equal ARV to 17 HCF (current government

plan)

ARV available for distribution only treat 10% of infected

Catchment region: do not know hence approx 40km

Distance from community to HCF is determinant of whether patient has access to treatment

HIV prevalence: urban = 13%, rural = 9%Only 51 communities in KwaZulu-Natal

Population > 500

Accessibility = how likely a patient will travel to a HCF to receive ARV

# Patients go to HCF: increase with # of patients, decrease with distance

Considered:# people in communityTreatment Accessibility function

Gaussian Radius of catchment region

Weighting function: distance btw community and HCFLongitudeLatitudeRadius of EarthAngles (rad)

Photo source: Wilson DP, Blower SM (2005) Designing equitable antiretroviral allocation strategies in resource-constrained countries. PLOS Medicine. DOI: 10.1371/journal.pmed.0020050

Spatial relation of HCF to neighbouring communities

ARV supply

Effective demand for each HCFLongitudeLatitude

Photo source: Wilson DP, Blower SM (2005) Designing equitable antiretroviral allocation strategies in resource-constrained countries. PLOS Medicine. DOI: 10.1371/journal.pmed.0020050

Purpose: find optimal equitable allocation strategy

Catchment region sizeNumber of HCF Total number of ARV Amount of ARV to each HCF

Precautions:Total ARV supplied = Total ARV distributed# ppl treated <= # HIV++ number of ARV to each HCP

Photo source: Wilson DP, Blower SM (2005) Designing equitable antiretroviral allocation strategies in resource-constrained countries. PLOS Medicine. DOI: 10.1371/journal.pmed.0020050

Majority ARV to HCF in Durban

2 non-Durban HCF have 5-15%

Other non-Durban HCF have <5%

When using current South Africa ARV roll out plan of 17 HCF

Compare using fixed 40km catchment regionIdeal: 10% patients receive ARV at each HCFCompare inter-quartile range:

1) All ARV to Durban:Small inter-quartile range; Unfair

2) Equal ARV to 17 HCF:Large inter-quartile range: 0.025-42% unequal

access1) 3) Authors’ OEAS:

Doesn’t necessarily deliver 10% to all patientsSmall inter-quartile range 0.011 – 10% treated

Photo source: Wilson DP, Blower SM (2005) Designing equitable antiretroviral allocation strategies in resource-constrained countries. PLOS Medicine. DOI: 10.1371/journal.pmed.0020050

Authors’ OEAS not perfect but gives best equality of ARV distribution

Equality improves SUBSTANTIALLY with either

# HCF used is more important than catchment size27 HCF

1) 20km 88% 2) 40km 91%3) 60km 96%

54 HCF1) 20km 90%2) 40km 94%3) 60km 99%

Photo source: Wilson DP, Blower SM (2005) Designing equitable antiretroviral allocation strategies in resource-constrained countries. PLOS Medicine. DOI: 10.1371/journal.pmed.0020050

Increase # HCF, SIGNIFICANTLY increase treatment accessibility

Propose: Increase in catchment region by increasing transportation

Use all 54 HCF, each with catchment region of 40-60km to maximize ARV distribution

Nigeria: Mobile clinic

Increase catchment region:Challenge: improve transportation costly

Use all 54 HCFAdvantage: existing infrastructureChallenge: training costly

Data: distance patients willing/able to travel to HCF

Data: factor in travel ease for all communitiesDifferent weighting function based on road

infrastructure, availability of transportation etc.

Authors chose equality as objective Other ethical ARV allocation strategies present

Need even access from national to grass root levelProportion to province, HCF, groups of individual

If uneven accessSocial, political structure destroyedIntra-state, inter-state conflict

1) Behavioural core groupsEg. sex workersChallenge: fraud to receive priority treatment

2) Highest viral loadAdvantage: easy to identify

3) Those s.t. reduce future epidemic impactAdvantage: potentially decrease future

epidemicDisadvantage: disregard current patients

(unethical?)

Our OEAS can be used by any resource-constrained country and highly recommended

Each nation has to decide on priorities of ARV distributionObjective function can be modified but OEAS

still apply

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