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

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

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

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  1. The contribution of rapid and non-rapid studiesto the GBD Hans Limburg MD, PhD, DCEH

  2. 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

  3. 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

  4. Blindness survey Focus >1 risk group lower prevalence Sample size >15,000 Detailed examination Disease intervention Expert staff Large survey population (10-100 m) Custom data analysis Takes long (years) Expensive (0.5-10 mln) Rapid assessment Focus on 1 risk group higher prevalence Sample size 2500-5000 Basic examination Planning and follow-up Local staff Smaller survey population (0.5-5 mil.) Automatic data analysis Rapid (months) Cheap (20-40,000 US$) RA versus conventional Survey

  5. The Gambia: Blindness by age 85% of blindness in people aged 50+

  6. Causes in people 50+ reflect causes in total population The Gambia: Causes of blindness

  7. CauseRapid assessment Cataract RACSS Trachoma TRA; ASTRA Onchocerciasis REMO; RAPLOA Childhood blindness CBS RE & low vision RARE Diabetic retinopathy DR module in RAAB Other rapid assessments in eye care

  8. Where surveys were done Custom survey RACSS RAAB

  9. 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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