Prehospital injury deaths: The missing link

International Classification of Disease based Injury Severity Score (ICISS): a comparison of methodologies applied to linked data from New South Wales, Australia

BACKGROUND

The International Classification of Disease Injury Severity Score (ICISS) provides an efficient method to determine injury severity in hospitalised injury patients. Injury severity metrics are of particular interest for the tracking of road transport injury rates and trends. The aims of this study were to calculate ICISS using linked morbidity and mortality datasets and to compare predictive ability of various methods and metrics.

METHODS

This was a retrospective analysis of Admitted Patient Data Collection records from New South Wales, Australia, linked with mortality data. Using a split sample approach, design data (2008-2014; n=1 035 174 periods of care) was used to derive survival risk ratios and calculate various ICISS scales based on in-hospital death and 3-month death. These scales were applied to testing data (2015-2017; n=575 306). Logistic regression modelling was used to determine model discrimination and calibration.

RESULTS

There were 12 347 (1.19%) in-hospital deaths and 29 275 (2.83%) 3-month deaths in the design data. Model discrimination ranged from acceptable to excellent (area under the curve 0.75-0.88). Serious injury (ICISS≤0.941) rates in the testing data varied, with a range of 10%-31% depending on the methodology. The 'worst injury' ICISS was always superior to 'multiplicative injury' ICISS in model discrimination and calibration.

CONCLUSIONS

In-hospital death and 3-month death were used to generate ICISS; the former is recommended for settings with a focus on short-term threat to life, such as in trauma care settings. The 3-month death approach is recommended for outcomes beyond immediate clinical care, such as injury compensation schemes.

International classification of disease based injury severity score (ICISS): A data linkage study of hospital and death data in Victoria, Australia

BACKGROUND

Surveillance of severe injury incidence and prevalence using ICD-based injury severity scores (ICISS) requires valid, locally applicable diagnosis-specific survival probabilities (DSPs). This study aims to derive and validate ICISS in Victoria, Australia, and compare various ICISS methodologies in terms of accuracy and calculated severe injury prevalence.

METHODS

This study used injury admissions (ICD-10-AM coded) from the Victorian Admitted Episodes Database (VAED) linked with death data (Cause of Death - Unit Record Files: CODURF). Using design data (July 2008 - June 2014; n = 720,759), various ICISS scales were derived, based on (i) in-hospital and (ii) three-month mortality. These scales were applied to testing data (July 2014 - December 2016; n = 334,363). Logistic regression modelling was used to determine model discrimination and calibration.

RESULTS

In the design data, there were 6,337(0.9%) hospital deaths and 17,514(2.4%) three-months deaths; in the testing data, there were 2,700(0.8%) hospital deaths and 8,425(2.5%) three-month deaths. Newly developed ICISS scales had acceptable to outstanding discrimination, with Area Under the Curve ranging from 0.758 to 0.910. Age-specific ICISS scales were superior to general ICISS scales in model discrimination but inferior in model calibration. Calculated severe injury (ICISS ≤0.941) prevalence in the testing data ranged from 2% to 24%, depending on which mortality outcomes were used to calculate DRGs.

CONCLUSIONS

This study provides local, validated ICISS scores that can be used in Victoria. It is recommended that age group stratified ICISS based on the worst-injury method is used. From the comparison of various ICISS scores, reflecting the range of ICISS permutations that are currently in use, care should be taken to compare ICISS methodology before comparing severe injury prevalence per population, injury cause, and time trends.

Opportunities to prevent fatalities due to injury: a cross-sectional comparison of prehospital and in-hospital fatal injury deaths in New Zealand

OBJECTIVE

There is interest in opportunities that lie in the prehospital setting to reduce the substantial burden of fatal injury. This study examines the epidemiology of prehospital and in-hospital fatal injury in New Zealand.

METHODS

All deaths registered in 2008-2012 with an underlying cause of death external cause-code V01-Y36 (ICD-10-AM) were identified. The setting of death was determined following linkage to, and review of, hospital discharge data and Coronial records.

RESULTS

Of 7,522 injury deaths, 80% occurred in a prehospital setting, with the highest burden relating to males. Within those fatally injured, 25-54-year-olds had a higher risk of prehospital death than 55-84-year-olds (adjusted Relative Risk [aRR] 1.20, 95%CI 1.16, 1.20). Similarly, those injured due to drowning (aRR 1.39, CI 1.26, 1.53) and non-hanging suffocation (aRR 1.31, CI 1.18, 1.45) had a higher risk of prehospital death than those 'struck by/machinery'.

CONCLUSION

Prehospital deaths account for four out of five fatal injuries in New Zealand. Of the fatally injured population, the probability of prehospital death differed by age, sex, injury mechanism and intent. Implications for public health: This study highlights the importance of strengthening prevention efforts to reduce the substantive burden of prehospital fatalities in New Zealand.

Potential survivability of prehospital injury deaths in New Zealand: a cross-sectional study

INTRODUCTION

Acknowledging a notable gap in available evidence, this study aimed to assess the survivability of prehospital injury deaths in New Zealand.

METHODS

A cross-sectional review of prehospital injury death postmortems (PM) undertaken during 2009-2012. Deaths without physical injuries (eg, drownings, suffocations, poisonings), where there was an incomplete body, or insufficient information in the PM, were excluded. Documented injuries were scored using the AIS and an ISS derived. Cases were classified as survivable (ISS <25), potentially survivable (ISS 25-49) and non-survivable (ISS >49).

RESULTS

Of the 1796 cases able to be ISS scored, 11% (n=193) had injuries classified as survivable, 28% (n=501) potentially survivable and 61% (n=1102) non-survivable. There were significant differences in survivability by age (p=0.017) and intent (p<0.0001). No difference in survivability was observed by sex, ethnicity, day of week, seasonality or distance to advanced-level hospital care. 'Non-survivable' injuries occurred more commonly among those with multiple injuries, transport-related injuries and aged 15-29 year. The majority of 'survivable' cases were deceased when found. Among those alive when found, around half had received either emergency medical services (EMS) or bystander care. One in five survivable cases were classified as having delays in receiving care.

DISCUSSION

In New Zealand, the majority of injured people who die before reaching hospital do so from non-survivable injuries. More than one third have either survivable or potentially survivable injuries, suggesting an increased need for appropriate bystander first aid, timeliness of EMS care and access to advanced-level hospital care.