Estimation or guestimation? (8)
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Dr Alan D. Lopez, Team Co-ordinator, Epidemiology and Burden of Disease,
World Health Organization responded:
Estimates or guestimates: CAUSE OF DEATH ESTIMATES
Your recent contribution to the AFRO-NET group concerning contradictory
cause of death estimates from WHO and UNAIDS has been brought to my at-
tention. I thing you entitled it "Estimation or guestimation?".
Your are absolutely right that WHO and other UN agencies need to harmo-
nize their estimation and dissemination efforts so that users of these
estimates do not receive contradictory information; and WHO, at least,
has recently done so. The new Director-General, Dr Brundtland, has cre-
ated a Global Programme on Evidence for Health Policy, one of whose
functions is to ensure that all epidemiological estimates issues by WHO
are internally consistent and NOT contradictory.
The estimates published in the 1999 World Health Report have been sub-
jected to this internal consistency check and are the official WHO es-
timates of death and disease burden until further notice. We intend to
update these estimates each year and each update will serve as the best
available WHO estimate for any specific disease, injury or risk factor.
This process only began in April 1999 and there is no guarantee that
the WHR 1999 estimates are consistent with estimates published by WHO
or other UN agencies e.g. UNAIDS prior to this date. Indeed, given the
adherence to strict criteria around evidence and internal consistency,
there may well be substantial differences with previous estimates.
A good example is malaria, which you mentioned in your network message.
Previous estimates of deaths by WHO ranged from 1.5 to 2.7 million each
year. We have carried out an intensive evidence-based review of studies
with malaria experts and believe the true annual mortality is closer to
1.1 million. The fact that estimates can change dramatically may be in-
convenient for advocates but surely it matters more that they are based
on a defensible, evidence-based scientific process.
WHO cannot decide what other UN agencies can or cannot claim about the
burden of various diseases. By taking concrete measures to avoid con-
flicting messages from within WHO, however, we hope that we can encour-
age other agencies to be equally circumspect about epidemiological
claims and base then on close collaboration with WHO. This process has
already started with UNAIDS and we looking forward to extending this
collaboration to other agencies.
I should also point out that global estimation of disease burden will
always be an imprecise science as long as the underlying data sources
are unreliable, as they are in large parts of the developing world. The
alternative is not to make estimates at all, but I an sure you would
agree that this is unhelpful for advocacy and public policy (and if WHO
does not make estimates, advocacy-based groups would!). Given this im-
pression, surely what matters more is not the ranking of disease bur-
den, but whether WHO and its partners agencies have appropriately quan-
tified diseases and being of major public health importance.
I trust that this provides the clarification you were looking for.
Dr Alan D. Lopez
Team Co-ordinator
Epidemiology and Burden of Disease
World Health Organization
1211 Geneva 27
Tel: +41-22-791-2374
Fax: +41-22-791-4328
mailto:lopeza@who.ch
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