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Understanding the mortality pattern experienced in South Africa is hampered due to poor quality and representativeness of routinely collected data, particularly in rural areas. Therefore, a mortality surveillance system using verbal autopsy (VA) procedures is used in the Agincourt Health and Demographic Surveillance System (HDSS) as a solution to this problem. This presentation discusses a re-validation of the Agincourt VA instrument for HIV/AIDS diagnoses and evaluate the effects on other communicable and non-communicable diseases in this era of health transition.
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Validation of verbal autopsies in rural South Africa: the influence of AIDS mortality
Annette A.M. Gerritsen, Kathleen Kahn, Stephen M.Tollman, Michel Garenne
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Re-validation Agincourt VA Instrument (1)How good is it in the AIDS era?
Agincourt Health and Demographic Surveillance System: verbal autopsy (VA) as mortality surveillance system
Validation 1992-1995:
‘satisfactory estimate of the frequency of causes of death among adults and children’
‘findings could reliably be used to inform local health planning and evaluation, and policy priorities‘
Pre-dated AIDS era: re-validation
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Re-validation Agincourt VA Instrument (2)
Validate the diagnoses obtained with the Agincourt VA questionnaire against hospital diagnoses by presenting cause specific mortality fractions (CSMFs), and measures of sensitivity and specificity, both for children and adults, to assess the performance of the VA on a group and individual level respectively.
Study objective
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VA validation methods (1)
• Reference diagnosis: hospital deaths (Jan 2001-Aug 2005): ICD-10 main cause of death assigned
• VA: open and closed section, use of treatments, lifestyle practices
• VA ICD-10 cause of death assigned by 2 medical practicioners
Comparing VA and hospital records
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VA validation methods (2)
• Grouping of ICD-10 codes using WHO mortality tabulation lists
• Performance of the VA at group level: compare CSMFs for the hospital records and the VA
• Validty of the VA diagnoses at the individual level: calculating sensitivity and specificity for each cause of death (main hospital diagnosis = reference)
• Validation of single diagnoses HIV disease, TB, respiratory TB, validation of combined diagnosis HIV/TB among different age categories
Comparing CSMFs (group level) and calculating Se and Sp (individual level)
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CSMFs from VA and hospital recordsCSMFs based on the VA closely appproximate those of the hospital records used as a reference diagnosis.
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Se and Sp VA diagnoses (1)Under 5 year olds: Se low, except for HIV/TB [broad CIs] and Sp high for malnutrition and pneumonia/OARI, low for diarrhoea and HIV/TB.
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Se and Sp VA diagnoses (2)5 years and above: Se low, except for HIV/TB, malaria, malignant neoplasms, diabetes and diseases of the circulatory system. Sp is high, only not for HIV/TB.
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HIV disease and TBIt is indeed difficult to distinguish these two diagnoses and they should be presented as one underlying cause.
Se combined diagnosis lowest in under 15 year olds, sp highest in those 50 years.
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VA questionnaire usefull for monitoring trends in causes of deathFindings of the earlier VA validation study still hold in the AIDS era.
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‘satisfactory estimate of the frequency of causes of death íncluding HIV/TB among adults and children’
‘findings can reliably be used to support planning and resource allocation, and evaluate community-based interventions’
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More information
Dr. Annette Gerritsen072-9640548annette.gerritsen@epiresult.comwww.epiresult.com
Questions?
December 2010
