# Presentation: 721247

## ICE on Injury Statistics Business Meeting, 6 June 2004 – Injury Indicators update

*Colin Cryer*
*Senior Research Fellow*

## Activities since Paris 2003

- Email to _[ADVICE-USERS@LISTSERV.CDC.GOV](mailto:ADVICE-USERS@LISTSERV.CDC.GOV)_
- Lee Annest:
- 2 indicator reports from CDC (USA)
- Yvette Holder
- Report: violence indicators (International)
- Saakje Mulder
- Eurocost (European)
- Indicators for priority setting (National)
- John Langley
- Report and paper: ICISS (Australia & New Zealand)
- Paper: Trends in neck of femur fracture (National)
- Paper: Trends in injury: service delivery effects versus real effects (National)
- New Zealand Injury Prevention Strategy [NZIPS] (National)
- Injury Outcome Indicators

## New Zealand Injury Prevention Strategy

- Injury Outcome Indicators
- ‘All injury’
- 6 priority areas
- Assault
- Workplace injury
- Suicide and deliberate self-harm
- Falls
- Motor vehicle traffic crashes
- Drowning and near-drowning
- Approach
- Identify current national indicators
- Identify generic fatal and serious non-fatal indicators
- Apply to priority areas
- Validate all using our ICEIInG criteria (Washington DC, 2001)

## A tool for investigating face validity	- Injury ICE, Washington 2001

**Case definition**
- The indicator should reflect the occurrence of injury satisfying some case definition of anatomical or physiological damage.
**Serious injury**
- The indicator should be based on events that are associated with significantly increased risk of impairment, functional limitation, disability of death, decreased quality of life, or increased cost.
**Case ascertainment**
- The probability of a case being ascertained should be independent of social, economic, and demographic factors, as well as service supply and access factors.
**Representativeness**
- The indicator should be derived from data that are inclusive or representative of the target population that the indicator aims to reflect.
**Data availability**
- It should be possible to use existing data systems, or it should be practical to develop new systems, to provide data for computing the indicator.
**Specification**
- The indicator should be fully specified to allow calculation to be consistent at any place and at any time.

**Notes:**
Much of the discussion around injury indicators at the 2001 ICE meeting was around getting agreement on criteria for validating injury indicators. As you know, validity can be judged in a number of different ways including content, concurrent, and predictive validity. The criteria that we discussed would be used to judge content validity.

What we came up with is shown here, and has been reproduced in the handout in your pack. The criteria suggest that an ideal indicator should:

Have a case definition based on diagnosis
Focus on serious injury – however that is defined
Have, as far as possible, unbiased case ascertainment
Be derived from data that are representative of the target population
Be based on existing data systems (or it should be practical to develop new data systems)
Be fully specified.

Many of the criteria focus solely on indicators of injury incidence, and within that on the characteristics of the incident cases.

## Generic fatal and serious non-fatal indicators

- Fatal *(Source: National mortality data)*
- Age-standardised mortality rate per 100,000 person years at risk.
- Number of injury deaths
- Serious non-fatal *(Source: National hospital discharge data)*
- Age-standardised serious non-fatal injury rate per 100,000 person years at risk.
- Number of cases of serious non-fatal injuries

## Definition of a serious non-fatal injury

- ICISS _<_ 0.941
- Implies:
- includes cases with an estimated probability of death of 5.9% or greater
- High threshold
- Only includes cases of injury that have a very high likelihood of admission to hospital
- Examples:
- Fracture of the neck of femur
- Intracranial injury (excluding concussion only cases)
- Injuries of nerves and spinal cord at neck level

## What is ICISS?

- ICD-based Injury Severity Score
- Threat-to-life anatomical severity of injury measure
- How are ICISS scores derived?:
- Survival probabilities calculated for every ICD-10-AM diagnosis
- from large data sets from which survival status is known
- Survival probabilities combined where multiple injuries
- Gives ICISS score
- (1 – ICISS score) = Pr (death)
- Note: also calculated for ICD-9-CM-A
- Retrospective trends based on both 9th and 10th revisions

## Validity of indicators - General findings

- Quality of data
- Few publications - None recent
- Overseas work indicates potential problems
- Potential threat to validity for all indicators
- National indicators
- Fatal injury indicators – Satisfy our validation criteria
- Non-fatal indicators - Significant threat to validity
- Generic indicators
- Satisfy our validation criteria (Fatal & Serious non-fatal)

## Trends in generic indicators – ‘all injury’

## Discussion

- Interesting findings
- Expect trends for deaths and injuries of this severity to be similar
- Reasons for differences:
- Data problems?
- Preventive activities selectively preventing deaths but not serious injury
- Case fatality rate falling – ie. effect of better treatment (eg Roberts BMJ 1996)
- Getting more seriously injured people to hospital before they die
- Other?
- Argument for combining fatal and serious non-fatal injury to overcome these problems
- Net effect: no decrease?

## Centre for Health Services Studies

- www.kent.ac.uk/chss