Ruzicka and Lopez (1990) have listed five criteria used by the World Health Organisation to assess fitness of country-level cause of death data for inclusion in its compilations. Firstly, the proportion of all deaths attributed to residual categories such as "Symptoms, signs and ill defined conditions" is within limits, say less than 10%. Secondly, the proportionate distribution of deaths by cause is consistent with the estimated mortality level for that country. Thirdly, no cause of death with a clear age-sex dependency has been incorrectly assigned. Fourthly, the age-sex distribution for major causes is consistent with what one may expect for each cause. Finally, data generated by the system are consistent with previous years. Note that these are basically plausibility checks. A data set failing these criteria is more likely to be biased. A data set satisfying these criteria may still not be usable, on account of poor statistical power of the generated estimates, and biases that are not readily noticeable. Building upon the criteria suggested by Ruzicka and Lopez (1990), we have identified the following nine criteria to assess the usability of any cause of death statistics:

1. Content validity of lay reporting systems, if any.
2. Adequate coverage and compliance.
3. Validity of statistics at sub-national levels of disaggregation.
4. Minimal usage of residual categories, such as unclassifiable, or ill-defined conditions.
5. Consistency of cause-specific mortality proportion with general mortality level.
6. Absence of incorrect assignment of causes with clear age-sex dependency.
7. Incidence of improbable age-sex distribution by cause is nil.
8. Consistency of cause specific mortality proportion over consecutive years.
9. Timely compilation and publication of the statistics.

           We examine, below, the usability of the cause of death statistics in India from the rural and urban areas respectively. We take up each usability criteria, discuss its implications briefly and then examine how India's cause of death statistics fares, using national statistics and state level statistics from Andhra Pradesh. Where required, we supplement the published statistics with information about Andhra Pradesh, available to us from our study on cause of death in Andhra Pradesh. We have called this the Andhra Pradesh Rural Cause of Death (APRCD) study, 1998.

           Design characteristics of the reporting system have a bearing on the usability of cause of death statistics. For example, changes in the guidelines of the international classification of causes of death (ICD) have been seen to cause reduction or increase in assignment of deaths to certain causes, depending on the specific changes brought by the particular version of the ICD. Analogously, guidelines for verbal autopsy can have some effect on the cause of death structure produced by the concerned cause of death reporting system.

           The verbal autopsy method has been studied and applied in many parts of the world. For example the demographic surveillance system (DSS) in Matlab, Bangladesh (Nahar et al 1985; Zimicki, 1990); assessment of child mortality in Latin America (Puffer and Serrano, 1973); monitoring endemic diseases in West Africa (Bradley and Gilles, 1984; Greenwood et al, 1987) in Kenya (Omondi-Odhiambo et al, 1984), Namibia (Mobley and Ties, 1996); in Phillipines (Kalter et al, 1990) and in India (Bang et al 1992; Awasthi and Pande, 1998). Much of the VA related work, however, remains unpublished. For example the WHO-UNICEF (1994) memorandum on measurement of cause-specific mortality in children cites many unpublished sources.

           The current knowledge base on feasibility and validity of VA is largely restricted to childhood mortality. The WHO-UNICEF memorandum, cited above, summarizes results of validation studies and has tabulated sensitivity and specificity of VA for detecting major causes of childhood death. In addition, the memorandum contains expert opinion about use of VA for investigation of causes of childhood death. This memorandum was the result of an internal consultation in December 1992 in which experts engaged in research and implementation of VA participated. Bang et al (1992) have used consensus development techniques to synthesize expert opinion on diagnostic criteria for identification of causes of childhood deaths. They have developed questionnaires incorporating local terminologies in their study area (Gadchiroli, Maharashtra) to generate the required information by verbal autopsy to satisfy the coding algorithm.

           Studies about the validity of VA in identifying causes of adult death have been undertaken recently (Garenne and Fontaine, 1989; LSHTM, 1993). Garene and Fontaine (1989) have reported their experience in Senegal. The London School of Hygiene and Tropical Medicine (LSHTM) workshop (1993) on verbal autopsy tools for adult deaths was conducted on the eve of a study in sub Saharan Africa. Proceedings of this workshop, cited above, documents a consensus of expert opinion about VA for adult deaths. The World Bank working paper by Hayes et al. (1989), is another summary and source of expert opinion. Chandramohan et al (1994) have published discussions at the LSHTM verbal autopsy workshop and have summarized all VA-based studies published upto mid-1993. Certain general design features are the key to wide applicability, efficiency and validity of data generated by a VA based cause of death reporting system. Over the years, some degree of consensus on major design issues has been achieved. I have drawn upon these sources in order, to critically examine the extent to which SCD-Rural meets the criteria of a good VA-based system.

           The structured questionnaires of the SCD-Rural system are systematically examined for each of the conditions included in the non-medical list, in the light of available research results on verbal autopsy. SCD-Rural seems to satisfy most of these criteria except that of reporting multiple causes of death. However, assigning multiple causes of death creates problems for aggregation and reporting of deaths by cause. Manton and Stallard (1984) analyzed multiple cause of death patterns in the USA. Although their preferred suggestion is to use patterns of failure as the basis of analysis, it may not be a feasible alternative considering the small sample sizes inherent in verbal autopsy-based statistics. To the extent that certain deaths are assigned to a combination of causes, there will be reduction in number of deaths reported under the respective component causes (LSHTM, 1993). A compromise may be to restrict the number of multiple causes of death to a manageable number and develop algorithms to distribute these to their component causes. Manton and Stallard’s (1984) study suggests that recording upto three multiple causes would include more than two third of deaths. Choosing the top three most probable causes contributing to death may help improve the accuracy of estimates and keep it manageable.

           The trade off between the open-ended interview and the structured questionnaire needs further elaboration. Although an open-ended interview format allows for the pursuit of unusual diagnostic clues not covered by a structured questionnaire, it requires more skilled interviewers. For example, comparatively lower assignments to unknown category have been achieved with physicians acting as interviewers (Greenwood et al 1987). Open-ended interviews and coding of cause based on the judgment of the interviewer reduces the inter-regional and inter-temporal comparability of cause of death statistics.

           Since SCD-Rural satisfies most of the general design criteria for VA, does it follow that the statistics generated by it would automatically be valid? Not necessarily. Validity of classification of deaths to particular causes will depend on characteristics of the cause of death per se, as also the content of the questionnaire and algorithm used for specific disease entities the latter two of which are discussed in the next sub section.