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Population Size Estimation and coverage calculation for MARPs and MARA Dave Burrows, Director AIDS Projects Management G PowerPoint Presentation
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Population Size Estimation and coverage calculation for MARPs and MARA Dave Burrows, Director AIDS Projects Management Group. “Coverage”. Perhaps the most mis-named, misused and least understood concept in HIV work Coverage means whatever the person using it chooses to mean

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slide1

Population Size Estimation

and coverage calculation

for MARPs and MARA

Dave Burrows, Director

AIDS Projects Management Group

coverage
“Coverage”
  • Perhaps the most mis-named, misused and least understood concept in HIV work
  • Coverage means whatever the person using it chooses to mean
  • Most common use: % of people ever reached (or reached in 1 year) with an intervention: this is an utterly useless statistic
  • If 100% of IDUs are reached once with education or a new needle & syringe, or if MSM or SW are reached once with education or a condom, it will have virtually no impact on a HIV epidemic
1 st problem is pse
1st problem is PSE
  • PSE increasingly needed for national HIV plans & GF projects: if do not know size of population, how can we estimate coverage after 5 or 6 years of programs + plan scale-up?
  • Whatever definition of coverage is used, it almost always begins with “% of X population (IDUs, MARA, etc)”
  • X population is the denominator for all further calculations related to coverage and its constituent parts: reach, regularity of reach, breadth of services, quality
  • To find X population, population size estimation (PSE) methods are used
why is pse so difficult
Why is PSE so difficult?
  • Some populations difficult to count, especially hidden, stigmatised
  • Usual epidemiological methods such as national household or schools surveys usually do not work
  • Definition problems: eg, IDU has “ever injected”, “injected in past month”, injected in past year”?
  • Even more difficult for MARA and MARY as most epidemiological statistics & estimates are not disaggregated by age (or sex)
pse methods
PSE Methods
  • Variety of methods available, but most include:
  • Consensus/ Delphi
  • Multiplier methods
  • Other potential methods
  • RDS: Respondent Driven Sampling
  • Social networks
consensus delphi
Consensus/ Delphi
  • Asks key informants to agree on number of people in X population
  • Can be done at:
  • National level
  • All levels from local to national
  • Local to national seems to generate most accurate numbers
  • Should be triangulated with other methods
multiplier methods
Multiplier methods
  • Recommended by UNAIDS for population size estimation, eg for reporting on UNGASS IDU indicator
  • Uses existing data source with survey data
  • Benchmark: Reliable, regularly collected data: IDUs accessing health services, drug treatment, overdose deaths
  • Multiplier: Survey of as broad a sample as possible (eg not just from treatment centres)
multiplier formula
Multiplier formula

X (population) = multiplier x benchmarkExample: 1000 IDUs entered drug treatment in 2007 (benchmark)

  • 10% of IDUs surveyed said they entered drug treatment in 2007 (multiplier)
    • X = 1000 x 10/100 (= 10)
    • X = 10,000 IDUs
triangulation
Triangulation
  • Single multiplier exercises tend to be inaccurate
  • UNAIDS recommends using 3 at least separate processes, and averaging results to find a mean estimate:
  • Eg: Different processes may give 10,000; 8000; 11,000. Mean = 9670
rds social networks
RDS/ Social networks
  • RDS uses snowball sampling in specific methods to attempt to achieve highly representative sampling: was not developed as a PSE method!
  • Mexico AIDS Conference: meta-analysis of 200 RDS papers found no evidence that RDS is useful in PSE
  • Promoted by many agencies with little/no evidence of accuracy; costly, time-consuming
  • Social networks PSE: new method, currently promoted by UNAIDS PSE workshops. May have value but requires evaluation, and to date apears costly and time-consuming
apmg tajikistan project
APMG Tajikistan project
  • In Tajikistan, APMG is finalising a 5-month process for UNDP (GF PR) to:
  • Estimate national populations of IDUs and SW
  • Risk behaviour of IDUs & SW in 5 sites
  • Capacity of implementation agencies to scale up service delivery to IDUs & SW in these sites
  • In addition, APMG is trying to tie this process to ongoing PSE for IDUs and SW as numbers change (especially locally as IDUs & SW are chased from 1 area by police activity or attracted to an area by availability of drugs or SW clients)
tajikistan pse methods
Tajikistan PSE methods
  • Expert estimation (Delphi) at rayon level, combined at oblast and national levels
  • Survey for risk assessment included multiplier question re use of narcological services in 2008
  • Benchmark: narcological statistics in 2008
  • Results presented to national consensus meeting (September 21) to agree final numbers
lessons learned from tajikistan
Lessons learned from Tajikistan
  • Biggest error was carrying out risk assessment and PSE simultaneously: much larger sample sizes needed for risk assessment sampling meant expert estimation could not be carried out in all rayons nationally
  • PSE can be relatively cheap and quick if done as a stand-alone activity
lessons learned from tajikistan14
Lessons learned from Tajikistan
  • Rayon-level estimation requires national/ oblast level staff to assist local officials to come to consensus
  • Time should be included to allow rayon estimates to be considered at oblast level, then national meeting based on oblast estimates
  • If this process used, could set up 6-monthly monitoring by asking rayons to consider increases/ decreases over the previous 6 months. Requires oblast/ national compilation
tajikistan lessons re mara
Tajikistan lessons re MARA
  • PSE of MARA in Tajikistan could be accomplished using the same methods (with lessons learned) BUT
  • Definition required
  • Definition would need to be agreed with officials from various departments
  • Definition to be explained at rayon level
armenia
Armenia
  • PSE of MARA in Armenia carried out by APMG and MoH staff working on GF RCC proposal (2008)
  • Had already estimated IDUs, MSM, SW, migrants, uniformed personnel
  • MoH wanted to include specific programs for MARA but this required a statement about projected coverage after 6 years
  • To calculate coverage figure, PSE was needed for MARA
armenia methods
Armenia Methods
  • No time available for MARA PSE study
  • Estimate figure was calculated as 5% of all adolescents in Armenia on the basis of household and school surveys that showed at least 5% of adolescents engaging in risky sexual behaviour or illicit (not necessarily injecting) drug use
  • Population estimate was used in RCC proposal with a note that a full PSE would be carried out as part of the grant activities
  • RCC was approved and will begin in late 09
macedonia
Macedonia
  • PSE in Macedonia will be carried out by National Public Health Institute (NPHI) for MoH (GF PR)
  • NPHI has decided to combine PSE with risk behaviour survey and to use RDS (against our advice)
  • APMG’s role will be to examine all documents (methods, instruments, sampling frames, data analysis & reports) to recommend corrections
  • From this process, we will be able to learn lessons about use of RDS for PSE (probably by end 09)
some further thoughts on coverage
Some further thoughts on Coverage
  • APMG accepts WHO Universal Access definition:

% of those who need an intervention who receive that intervention

  • APMG sees 3 aspects:
  • Reach, including regularity of reach. What % of the total population participate? Is this a sufficient proportion to prevent/ reverse/ treat the epidemic?
  • Breadth: Spectrum of Services. Are interventions able to prevent/ reverse/ treat the epidemic?
  • Quality: Are interventions sufficiently attractive and effective to meet their objectives?
coverage calculation
Coverage Calculation
  • APMG accepts WHO Universal Access definition:

% of those who need an intervention who receive that intervention

  • E.g., for needle-syringe programs, it appears that a percentage of IDUs in a specified area need to access NSP of adequate quality ON A REGULAR BASIS to prevent/ reverse a HIV epidemic among IDUs.
  • WHO, UNODC and UNAIDS state that the % of IDUs who have been reached by NSP regularly (at least monthly for past 12 months) should be considered as:

Low coverage: <20%

Medium coverage : >20– <60%

High coverage : >60%

coverage questions
Coverage questions
  • WHO, UNODC and UNAIDS Target Setting Guide for IDUs include:
  • Proportion of IDUs regularly reached by NSP
  • Number of pharmacies/ 1000 IDUs
  • NSP sites/ 1000 IDUs
  • Number of syringes distributed per IDU per year
  • % of IDUs who have been reached by NSP regularly (at least monthly for past 12 months)
  • % of IDUs who have been reached by NSP in the past month
coverage questions 2
Coverage questions 2
  • Similar questions on proportion of IDUs in substitution treatment
  • Similar questions on proportion of IDUs in other drug dependence treatment
  • Similar questions on proportion of IDUs participating in VCT and know their results
  • Ratio of HIV+ IDUs receiving ART to non-IDU HIV+ receiving ART (relative to proportions of HIV+ population)
  • Questions on TB, hepatitis C, etc
quality
Quality
  • Generally, view is that quality should be measured by adherence to guidelines, e.g. target setting guide asks:
  • Percentage of NSP sites adhering to WHO guidelines on NSP
  • Percentage of NSP sites adhering to UNAIDS best practice recommendations for HIV prevention among IDUs
  • Percentage of occasions when clients access an NSP and receive IEC
  • Percentage of occasions when clients access an NSP and receive condoms
  • In Russia, APMG is helping Russian Harm Reduction Network to develop NSP quality measurement and improvement processes based on the WHO/ UNAIDS/ UNODC Guide to Starting and Managing NSPs
  • Manual plus instruments should be available in English & Russian early 2010
coverage for other marps
Coverage for other MARPs
  • Similar processes now under way for MSM:
  • APMG working with Amfar, UNDP & WHO on coverage calculation, targets & breadth of services
  • WHO working on similar processes re SW
  • MARA and MARY not yet really included in these global processes