The UNAIDS Reference Group raises an important issue in the approach to mortality estimation, claiming that their methods and, more importantly, their data sources to estimate mortality from HIV/AIDS are sufficiently robust to obviate the need for any post-estimation review. We disagree.
Underlying their claim is the notion that causes of death, particularly those of global significance such as HIV/AIDS, can be reliably estimated without taking into account what might well be reasonably reliable estimates of other major causes of death, estimated from reasonable data sources, with reasonably defensible methods. The implication of this claim is that when such reasonable estimates of cause-specific mortality are summed for any given age-sex group of the population for any given year, the total might well exceed the numbers of deaths that have been independently estimated from available demographic data on mortality levels in populations.
Are we to conclude that overall estimates of mortality are thus less reliable than estimates of cause-specific mortality, even for causes where substantial effort has gone into data collection? Again, we think not. Demography and the measurement of mortality in populations has a substantially longer history than does descriptive epidemiology, certainly for HIV/AIDS, with the result that there are vastly more datasets available with which to estimate all-cause mortality, including for countries most affected by HIV/AIDS.1
Uncertainty intervals for total mortality are substantially smaller than for any single cause of death of significance in most countries.2
This observation underlies the approach to cause of death estimation in the Global Burden of Disease (GBD) 2010 Study.3
In its application, we adjust individual causes in proportion to the estimated degree of uncertainty around each: we do not thus assume that initial cause-specific estimates are equally valid, as Hallet and colleagues suggest.3
Causes such as HIV/AIDS are proportionately less adjusted since uncertainty around the initial estimates (provided in large part by UNAIDS) is less than for other causes.
Despite the numerical differences between GBD 2010 and UNAIDS, the current estimates of global HIV/AIDS deaths are within the uncertainty bounds of the GBD 2010 estimate, and, more importantly, show a similar trend in HIV/AIDS mortality over time.4
Reasonable scientists will continue to debate the scientific merits of different methodological approaches to the estimation and the interpretation of inadequate data; that is the scientific process and we should not suppress such debate and innovation. Rather, we should seek to rapidly reduce uncertainty in our understanding of causes of death in populations by accelerating efforts to assist countries to strengthen their vital registration systems. That is surely a goal we can all agree on.
We declare that we have no conflicts of interest.