To our knowledge this is the only recent study with the aim of developing and validating a new mortality estimation method based on primary data collection. The informant method potentially offers a more rapid means of estimating mortality than retrospective surveys and surveillance systems. The results show that the informant method performed better than the active surveillance system in the Tanzania refugee camps, but achieved moderate sensitivity compared with a best estimate of mortality, and was not good at identifying deaths in children <5 years of age. The informant method also cannot be used to record data on exposure to mortality risk factors, whereas retrospective surveys can potentially record such data.
There are different reasons why the informant method did not identify some deaths. The choice of key informants may have been sub-optimal and inappropriate for childhood deaths. This may have arisen because of dominance of community leaders among FGD participants, which may have masked the diversity of opinions in the community and discouraged other participants from expressing their views, resulting in over-direction by community leaders about which key informants we used. Furthermore, in both Kabul and Chiradzulu, key informants derived their information about deaths from similar sources. A greater number and diversity of key informants may have been warranted.
It may have been inherently difficult for key informants to know about all deaths in their sectors, due to: (i) large sector populations (about 3000 people in Kabul, 2000 in Mae La and 4500 in Tanzania); (ii) lack of trust and thus information sharing between key informants and community members (e.g. in Kabul many residents were short-term renters without kinship ties to the wakils); and (iii) inexperience of key informants (e.g. in Mae La many section leaders were newly appointed as part of a repatriation scheme).
Household respondents provided a minority of all referrals; given the relatively low mortality in the study sites, this may have been because households did not know about other deaths. Additionally, households may have been reticent to share such information with strangers, wary of upsetting community leaders or the bereaved families themselves or acting based on other cultural and/or religious beliefs and practices.
Both key informants and households may also have deliberately withheld information on deaths due to sensitive causes, such as suicide or drug addiction. This issue would, however, affect alternative mortality measurement methods and hence is not a particular weakness of this method. Furthermore, the main mortality rate estimate would not be affected if these deaths were mentioned, but falsely attributed to a more socially acceptable cause.
Theoretically, the informant method presents considerable advantages over both surveillance and surveys for the purposes of real-time mortality measurement. It is a one-off activity that can be repeated on a regular basis by staff with limited research skills. The small number of interviews conducted (i.e. only in households with deaths) greatly reduces data entry requirements; a simple analysis can be done with pen and paper, as there is no need for weighting and design effect adjustment; and the questionnaire can be expanded to explore the timing/location of the death (e.g. if the death occurred when residing in the study site or beforehand) and the causes and circumstances of death through methods such as verbal autopsy, since considerably more interview time can be devoted to each household than for other methods. The findings on issues of feasibility of the new method (e.g. time, financial, use of verbal autopsy questionnaires and ethical implications) will be presented elsewhere. A potential disadvantage is the need for accurate population estimation. However, population estimation is frequently required by humanitarian agencies for operational response in crisis-affected and resource-poor settings, and so is itself a useful measurement activity. Like retrospective surveys (but not surveillance), the informant method is also affected by potential survival bias (households disintegrating during the course of the recall period), though the potential effect of this bias may be small in our case due to the short recall period.
The method's sensitivity did not reach 80%, the level we aimed for when developing this method. Based upon our experience of developing and testing the method, we speculate that it may be possible to increase sensitivity by: (i) ensuring that the FGD participants represent a mix of men and women, ages, occupations and economic and social hierarchies; (ii) using multiple rounds of FGDs; (iii) using other formative research methods alongside FGDs, such as in-depth individual interviews or informal discussions; (iv) using more than two informants: in this study, we easily collected additional lists of deaths and; (v) using less formal informants (e.g. groups of people at gathering points such as water sources, shops).