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Rapid assessment

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					The contribution of rapid
 and non-rapid studies
      to the GBD


 Hans Limburg MD, PhD, DCEH
    Rapid Assessment of
 Avoidable Blindness (RAAB)
• Population based survey
• Focus on people aged 50+
  – High prevalence  lower sample size
• Standardised survey form
• Special software
  –   Calculation of sample size
  –   Random selection of clusters with pps
  –   Data entry with consistency checks
  –   Automatic generation of reports
  –   Results comparable worldwide
How representative is RAAB?

• Survey area with population 0.5 - 5.0 million
• Cluster size: 50 residents age 50+
• Usually 50 to 100 clusters
• Random selection of population units from
  sampling frame with PPS
• Selection of 50 eligible persons from population
  unit with compact segment sampling
• In-build data cleaning functions
• Age and sex adjustment of prevalence
RA versus conventional Survey
Blindness survey            Rapid assessment
• Focus >1 risk group       • Focus on 1 risk group
    – lower prevalence          – higher prevalence
• Sample size >15,000       • Sample size 2500-5000
• Detailed examination      • Basic examination
• Disease intervention      • Planning and follow-up
• Expert staff              • Local staff
• Large survey population   • Smaller survey
  (10-100 m)                  population (0.5-5 mil.)
• Custom data analysis      • Automatic data analysis
• Takes long (years)        • Rapid (months)
• Expensive (0.5-10 mln)    • Cheap (20-40,000 US$)
The Gambia: Blindness by age

                 16
                 14
                 12        85% of blindness in
Prevalence (%)




                 10         people aged 50+
                 8
                 6
                 4
                 2
                 0
                      0-   10-   20-   30-   40-   50-   60-   70-   80+
                                        Age (years)
          The in people 50+ reflect
        CausesGambia: Causes of
         causes in total population
                 blindness
Cause of           Total      Population 50+
blindness        population
Cataract            46%            48%

Aphakia             13%            15%

Trachoma/CO         22%            17%

Glaucoma            9%             11%

Other               11%            9%
      Other rapid assessments
             in eye care

Cause                    Rapid assessment
• Cataract               RACSS
• Trachoma               TRA; ASTRA
• Onchocerciasis         REMO; RAPLOA
• Childhood blindness    CBS
• RE & low vision        RARE
• Diabetic retinopathy   DR module in RAAB
Where surveys were done
 RACSS   RAAB   Custom survey
       Web-based repository for
    results from blindness surveys
•   Increasingly difficult to publish results
•   Not all results in publication
•   Risk of losing original data and reports
•   Study results in public domain
•   Enable researchers to combine data
•   Permission:
    – Address principal investigator
    – Reports generated by software
    – Original data as Excel file

				
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posted:1/23/2013
language:English
pages:9