Potential and limits of verbal autopsies

The idea of assessing causes of death by retrospective interview is as old as medical statistics. In 17th century London, so-called death searchers visited the houses of people who had died to make enquiries about the death, especially about communicable diseases. In the 19th century, modern systems of death registration saw the end of this practice in Europe; but in developing countries, which lack the medical capacity to produce death certificates for the whole population, there is still a need for lay investigations into cause of death. Pioneer projects in the 1950s and 60s in Asia (Khanna and Narangwal in India, Companiganj in Bangladesh) and in Africa (Keneba in the Gambia) used systematic interviews by well trained physicians to assess causes of death. Workers at the Narangwal project christened this new technique autopsy. However, in-depth interviews by research physicians are costly and can not be replicated nationwide, and sometimes involve biases linked to the focus of the research. Systematic investigation of causes of death on a larger scale became possible with the use of questionnaires. Questionnaire-based verbal autopsies have several advantages over ad hoc investigations. For example, they allow all available information to be recorded and, although data derived from these interviews do not constitute formal proof, they do allow objective decisions about probable cause. WHO has long recommended the systematic recording of signs and symptoms for assessing causes of death, and has proposed structured questionnaires for use in developing countries. (1-3) When the list of target diseases is extensive, questionnaire-based verbal autopsies may, in principle, ensure high specificity. They can be administered by lay people, and qualified personnel need only read the forms and stories. They also allow statistical analysis and the use of systematic algorithms. Many questionnaires have been developed since the Reproductive Age Mortality Studies (RAMOS), Matlab, and Niakhar questionaires were produced in the late 1970s and early 80s. These tools are now used in many research settings, such as the INDEPTH network, and also in national or large-scale regional surveys (such as in Morocco, India, and China). (4) Verbal autopsies are of optimum value when they are applied to all deaths in a population, which is crucial in situations where only a fraction of deaths are registered or occur in hospitals. However, there are limits to the use of verbal autopsies. First, they require skilled field-based personnel to record evidence as well as office-based staff to assess cause of death, and to code and analyse data. Second, the list of causes of death that can be assessed by verbal autopsy is only a small sample of the list of causes used on medical certificates. Third, the quality of the assessment depends on sensitivity and specificity of each diagnosis. While they work well for some diseases of high public health importance (such as measles, whooping cough, tetanus, cholera, and dysentery) as well as for accident and violence, the use of verbal autopsy is more problematic with diseases that have less specific symptoms, but which are equally important (such as HIV/MDS in children, malaria in adults, and cancers). …