Measuring cause specific mortality: the use of verbal autopsies

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Measuring cause specific mortality the use of
verbal autopsies Alan Lopez Chalapati Rao
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Uses of cause of death data

• To study and explain levels, trends and
  differentials in age specific mortality
  (Preston and disciples)
• To guide priorities for resource allocation for
  intervention programs, biomedical and
  sociomedical research
• To monitor public health programs
• To provide clues for epidemiological research

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Sources of national cause-specific mortality data

• vital registration systems GOLD STANDARD
• sample registration systems
• household surveys
• population laboratories and surveillance systems
• epidemiological estimates
• For deaths registered in these systems, cause of
  death is either
• certified by a medical practitioner
• based on "verbal autopsies"
• not given at all

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VR Data availability, around 2000
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Data quality
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Strategies to improve COD data availability

• Accelerate development of civil registration
• SLOW, EXPENSIVE, LOW GOVERNMENT PRIORITY
• Introduce / improve physician certification, ICD
  coding, and statistical processing of data
• CRITICAL, NEEDS BIG WHO PUSH, NO CHAMPIONS
• Introduce and develop local applications of
  verbal autopsy procedures for data acquisition
  through
• vital registration
• sample registration
• demographic surveillance systems
• household surveys

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What is VA ?

• VERBAL AUTOPSY (VA), a two step procedure
• Data collection interview of bereaved relatives
  to collect information on symptoms experienced by
  deceased before death, using some form of survey
  instrument
• COD assignment methods include
• physician review of VA data
• ICD certification, coding, and tabulation
• computerised algorithms for population fractions

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Principles of VA

• Based on recall by relatives of symptoms \
  illness prior to death, sometimes difficult for
  adult deaths (similar symptoms)
• Requires identification of clearly
  distinguishable symptom complexes for each cause
  of interest, not available for some adult causes
• lung cancer, TB, diabetes, different forms of
  liver disease etc
• So far, found useful and validated for infant and
  maternal deaths deaths due to injuries
• Recent experiences suggest utility of gathering
  information from medical documents if available
  within household

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Historical use of VA

• Measuring cause specific mortality in populations
• SCDR / SRS - India
• DSP / VR China
• AMMP (Tanzania)
• Investigating COD in specific age-sex cause
  groups
• infant / child deaths
• maternal causes of death
• Injury related deaths
• Investigating outbreaks / epidemics
• Ebola fever epidemic in West Africa
• Diarrhoeal disease in Bangladesh

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Historical use (contd)

• Assessing coverage and effectiveness of disease
  specific interventions
• insecticide impregnated bed nets in Africa
• Pneumococcal vaccine trials in Bohol
• Home based neonatal care in India
• In developed countries
• confidential enquiries of maternal mortality
• Sudden infant death syndrome
• QOL / mental health status in terminal illness
  among elderly

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VA in India

• Survey of causes of death rural (SCDR) 1967
  1998 (1400 PHCs, rep)
• Structured instrument, lay assignment of cause,
  ICD classification since 1996
• problems with incomplete coverage, inadequate
  investigator training / physician verification of
  cause
• New system being implemented in SRS, covering 8
  million
• New instruments, field protocols, training
  support
• Five year retrospective survey planned soon
• independent field studies by Ind C Med Res in 5
  zones, ? 1 million pop each
• Need for integrated approach, involving civil
  registration systems

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SCDR Results
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VA in China

• Two mortality statistics systems NMS, DSP
• NMS (VR) medical certification (urban) / lay
  reporting (rural) 120 m pop
• DSP 1981, now 145 points, nationally
  representative, 10 m pop
• medical certification / VA for household deaths
  (80)
• Semi structured instrument, physician COD
  assignment, ICD classification since 1987
• Household visit by township hospital staff
• Much reliance on free text response to What was
  the cause of death in this person?
• Use of supportive medical documentation available
  at home / from hospital records
• Needs to be tested for reliability, and if
  possible, validity
• Research projects underway (UQ, Harvard)

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DSP Results
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VA in Tanzania

• Adult morbidity and mortality project in 3
  districts
• 1992 onwards
• Instruments developed by LSHTM AMMP
• Physician assignment of cause
• Non ICD mortality classification
• Recent introduction of ICD certification / coding
  (2003)
• Validation study underway (UQ, Harvard, LSHTM)

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AMMP results - 2000
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Important issues in VA

• Standard survey instruments including modules for
• Free text narrative
• Structured questions
• Recording household medical document information
• Interviewer
• Education background, training
• Choice of respondent
• Proximity to deceased, education, age and sex,
  cultural factors
• Recall periods
• Minimum and maximum intervals
• Cause of death assignment and ICD coding
• Physician / trained health professional review
  using standard protocols
• Computerized programs
• ICD mortality tabulation lists
• Validation studies

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Validation studies

• To develop standard verbal autopsy instruments
  and procedures that are applicable in different
  epidemiological and cultural settings with
  minimal modifications
• To measure biases in community cause of death
  patterns when using VA instruments validated in
  hospital based studies
• To improve understanding of quality of cause of
  death information for estimating global and
  regional mortality patterns

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Methods

• VA validation study in Tanzania
• VA validation and mortality statistics evaluation
  study in China

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Study design - Tanzania
For each death 3000 deaths
Medical record
Verbal autopsy
DC/ underlying cause from reviewer 1
DC/ underlying cause from reviewer 2
DC/ underlying cause from reviewer 1
DC/ underlying cause from reviewer 2
Agreement
Disagreement reconciled by consensus
Agreement
VA Underlying cause
MR Underlying cause
Verbal autopsy validation
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Study design - China
2700 deaths
Routine system death certificate
Routine system validation urban areas
Medical record Death certificate
1900 deaths
3500 deaths
Routine system reliability rural areas
Verbal autopsy death certificate
Verbal autopsy validation
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Future research

• Gates proposal Africa, Bangladesh, Philippines
• New UQ sites in Indonesia, Thailand
• Egypt, Syria, other EMRO countries ?
• Expression of interest by Indian SRS to adopt WHO
  VA methodology ?
• Other opportunities in Africa through PEPFAR?

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Conclusions

• Information on symptoms could be combined with
  available clinical evidence for judging cause of
  death at individual level
• Scope for application of Bayesian principles in
  deriving population level cause specific
  mortality fractions from data gathered in surveys
• For adult deaths, could be useful for
  understanding broad cause group mortality at
  population level
• A measure of discriminatory power of individual
  questions / algorithms for identifying specific
  causes of adult deaths would be useful

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Conclusions (contd)

• Need to evaluate biases from VA instrument
  validation in hospital studies, and cross
  cultural comparability of responses to specific
  questionnaire items
• Need for standardization of protocols for both
  data collection and cause of death assignment
• All VA implementation should contain elements of
  validation
• Examples of potential application
• Sentinel sites in northern Brazil
• Representative sites in Tanzania
• Data quality improvement in Thailand, China
• No other option to rapidly increase usability of
  cause of death data from developing countries