Survival risk ratios for ICD-10-AM injury diagnosis classifications for children

The survival risk ratios (SRRs) were calculated using linked hospitalisation and mortality data from Australia. Hospital admissions was obtained from each Health Department or the Australian Institute of Health and Welfare and included all injury-related admissions identified using a principal diagnosis of injury (ICD-10-AM: S00-T89) of children aged ≤16 years during 1 July 2002 to 30 June 2012. In the Australian Capital Territory (ACT) data were only available from 1 July 2004. Mortality data was obtained from the National Death Index. Hospitalisation and mortality data were probabilistic linked by the Australian Institute of Health and Welfare Data Linkage Unit. There were an estimated population of 4.5 million children aged ≤16 years in Australia.

The SRRs were calculated for each injury diagnosis. A SRR represents the ratio of the number of individuals with each injury diagnosis who did not die to the total number of individuals with the injury diagnosis. The SRRs can be used to estimate injury severity (i.e. the International Classification of Injury Severity Score: ICISS). The ICISS is calculated by applying the SRRs to each injury diagnosis code in your data. A SRR represents the ratio of the number of children with each injury diagnosis who did not die to the total number of children with the injury diagnosis. There are two methods commonly used to estimate ICISS values: (i) multiplicative-injury ICISS where ICISS is the product of all SRRs for each of the child’s injuries; and (ii) single worst-injury, where ICISS only includes the worst-injury (i.e. the injury diagnosis with the lowest SRR) as the single worst-injury.