Population Size Estimation and coverage calculation for MARPs and MARA Dave Burrows, Director AIDS...
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Transcript of Population Size Estimation and coverage calculation for MARPs and MARA Dave Burrows, Director AIDS...
Population Size Estimation
and coverage calculation
for MARPs and MARA
Dave Burrows, DirectorAIDS 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
11stst problem is PSE 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)
PSEPSE Methods Methods Variety of methods available, but most include: Consensus/ Delphi Multiplier methods
Other potential methods RDS: Respondent Driven Sampling Social networks
Consensus/ DelphiConsensus/ 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 methodsRecommended 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 formulaMultiplier formulaX (population) = multiplier x benchmark
Example: 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
TriangulationSingle 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 networksRDS/ 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 projectAPMG 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 methodsTajikistan PSE methodsExpert estimation (Delphi) at rayon level,
combined at oblast and national levelsSurvey for risk assessment included
multiplier question re use of narcological services in 2008
Benchmark: narcological statistics in 2008Results presented to national consensus
meeting (September 21) to agree final numbers
Lessons learned from TajikistanLessons learned from TajikistanBiggest 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 TajikistanLessons 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 MARATajikistan lessons re MARAPSE 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 departmentsDefinition to be explained at rayon level
ArmeniaArmenia 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 MethodsArmenia 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
MacedoniaMacedonia 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 CoverageSome 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?
CoverageCoverage Calculation 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%
CoverageCoverage questions questionsWHO, 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
CoverageCoverage questions 2 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
QualityQuality 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 MARPsCoverage 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