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– had no data reported, or none reported since 1990. Thailand had usable data reported, but it was<br />

considered to be of poor quality. 12<br />

The problems introduced by requiring reporting in health facilities and using a classification system<br />

designed for use in HICs results in incomplete and poor quality data reported to WHO. Extensive<br />

adjustments are required in order to make use of this data. However, the multiple biases are not<br />

systematic and the poor quality of the data makes adjustment a very difficult process.<br />

1.6 ADJUSTING INCOMPLETE NATIONAL DATA FOR GLOBAL ESTIMATES<br />

Lacking complete and accurate reports from its member states, WHO has had to develop a process to<br />

correct and adjust reported data, as well as to impute missing drowning data. The process of<br />

completing, imputing and adjusting the reported mortality data for use in constructing the Global<br />

Burden of Disease (GBD) estimates is described in detail elsewhere. 13 A brief summary of the GBD 2004<br />

process that resulted in the estimations for the time period covered by the TASC-UNICEF country<br />

surveys follows:<br />

The first step was to indirectly estimate age-specific death rates by sex, using life tables<br />

derived from available data. The data were adjusted for coverage and completeness.<br />

Adjustments were made by reclassifying misclassified deaths and reassigning and<br />

redistributing deaths coded to partially-specified causes.<br />

Injury deaths, including drowning, were estimated by statistical models (GBD CODMOD -<br />

case of death model) and regional patterns of death.<br />

Mortality rates were constructed for 21 causes of death used in the GBD process. Once<br />

constructed, expert groups undertook country-level analyses to establish national rates for<br />

mortality by age, sex and cause, and adjusted for internal consistency and validity.<br />

The lack of reporting of fatal drowning in national information systems requires the use of this<br />

adjustment process, which starts with large underestimates and corrects them by external adjustment.<br />

The complexity of the processes, the uncertainties involved in the adjustments, and the multiple nonlinear<br />

sources of possible bias make this a process fraught with potential for error.<br />

Some of this potential for error is due to the need to impute, estimate and adjust, but it is also in part<br />

due to definitional issues and problems in the ICD classification system. This can be seen with data from<br />

HICs in Asia-Pacific. These data come from death registries, coronial reports and other national systems<br />

that are far more complete and accurate than those used in Asian LMICs. Because of this, they are much<br />

less likely to require imputation and/or estimations through modeling. However, there are still<br />

significant differences when compared with GBD estimates. For example, in Australia, differences<br />

between GBD 2004 data and those produced by the Royal Life Saving Society Australia (RLSSA) for<br />

similar periods, show the GBD figures underestimate fatal drowning by more than 50 per cent. 14<br />

Following the GBD 2004 estimates, a second GBD process was undertaken to estimate the drowning<br />

rates and numbers of drowning for a 2008 update. Some of the difficulty and the inherent uncertainty<br />

12<br />

Mathers, c. et al. (2005). ‘Counting the Dead and What They Died from: An assessment of global status of cause of death data’. Bulletin of the<br />

World Health Organization, 83:171-177.<br />

13 World Health Organization, Global Burden of Disease 2004 Update, Annex B, Data Sources and Methods, Geneva: WHO.<br />

14 World Health Organization, Global Burden of Disease 2004 figure 186 for Australia and Royal Life Saving Society Australia,<br />

National <strong>Drowning</strong> Report 2011 figure (p. 3) is 286 for the 2004-2005 time period, a difference of 54 per cent.<br />

23

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