# Presentation: 485223

## An Indicator for mortality: Thinking beyond external cause!(a.k.a.  selecting a main injury) 

- Margaret Warner, Ph.D.
- Li-Hui Chen, Ph.D.
- Rolf Gedeborg,
- Injury ICE meeting, Mexico 2008

**Notes:**
Very preliminary speaking notes!
Good Morning.  My name is Margaret Warner.  I’m from the National Center for Health Statistics.
I am going to talk about the main injury indicator.  Some of you who have been to ICE meetings before will remember this work talked about before as “selecting a main injury” 
I would like to acknowledge Lily and Rolf Gedeborg who contributed to this work in addition to Lois my supervisor.
I have been able to devote a substancial amount of time to this project because in the US we would like to include the “main injury” for the death on the MCOD file  -- presumably this would be used as an indicator.  I am going to walk you through over 10 years of ICE work in 15 minutes  -- focusing of course, on our most recent work which is a report to the mortality reference group on selecting a main injury (in your packet?) 

## Problem: Countries collect and report multiple cause of death data differently

- Past ICE work:
- Average number of injuries per death reported varies between countries collecting MCOD data
- Existing  systems
- No coding multiple cause of death
- Coding all causes, do not select main injury
- Coding all causes and select a main injury
- Coding only a main injury

**Notes:**
Very preliminary speaking notes!
No complex analysis needed here!
In Canada, for instance, they do not collect mc data on injuries
In the US, we collect and code all causes but we do not select a main injury
In England and Wales, they collect, code and select a main injury
I know there are countries that only code one main injury (in other words, select one and then code it)

## Request from the Mortality Reference Group (MRG)

- Who is the MRG?
- 	Part of WHO classification group who (1) decides on applications and interpretation of the ICD to mortality and  (2) recommends updates to ICD
- MRG asked ICE to provide guidance to the
- 	Selection criteria changed in ICD-10
- 	Concerns over application of new criteria voiced
- Selection criteria in ICD-9 and ICD-10:
- 		ICD-9	   Selects most  “severe” (referred to as the 			   Precedence list)
- 		ICD-10  Selects the injury which led to the death                  		            (similar to external cause selection)

**Notes:**
Very preliminary speaking notes!
So now I am going to talk about selecting a main injury...  Having looked at the US data, I think it may be important to select a main injury since some of the reason that some deaths have one injury and some deaths have many injuries may not be due to the death...  I suspect this is true internationally.

Here are some of the downsides to selecting and some of the things the MCOD group have been discussing.

## Selecting a main injury: Recommendations from MRG

- Eliminate trivial injuries and superficial injuries from consideration
- If obvious causal sequence, select injury which led to death
- Select from among remaining injuries using severity ranking
- Select first mentioned if several at same level of severity

**Notes:**
Very preliminary speaking notes!
The MRG came up with guideline which incorporate both the ICD -9 and ICD-10 guidelines. 

## Solution: Develop severity measures 

**Severity ranking empirically derived based on Swedish data**
**Use Survival Risk Ratios (SRRs) to determine severity ranking **
- SRR is probability of survival with a range from 0 (unsurvivable) to 1 (no threat to life).

**Notes:**
Very preliminary speaking notes!
Breif overview of what we did...  The data is really important – we tried a lot of different methods to deal with the fact that you need to include pre-hospital deaths.  In the US the hospital data and mortality data use different ICD coding systems and are not linked.  We tried to use the IMD matrix and the Barell matrix to combine but that was not working very well – AND then Rolf showed up with the perfect data set and he is going to talk about it for a few minutes.

## Swedish injury data	

**Unique person identification number**
**All residents** of Sweden have** equal access** to health services (tax funded). It is a **public sector responsibility**
- The National Hospital Discharge Register – future research, not insurance, reimbursement etc.
- Nation-wide and population-based
**Cause of injury** - low proportion missing (~4%)

## Swedish injury data

- 1998-2004
- Person-based linked National Hospital Discharge Registry and Cause of Death Registry
- Hospital and department transfers merged
- 733,131 incident injury admissions [Epidemiology, Accepted 2008]
- Superficial injuries (defined by MRG) excluded

## SRRs calculated for each injury ICD-10 code for total injury deaths.

SRRcode= SHcode/(SHcode + Dcode),
where code=any non-excluded ICD-10 S or T code
SHcode = weighted total mentions of survived hospital for each code  
Dcode = weighted total mentions of in-hospital deaths + pre-hospital deaths for each code
where weighted total mention = 1/number of ICD codes reported for death 

SRRs for ICD injury codes were ranked into 6 ordinal levels of severity with roughly equal numbers of deaths in each severity level.

**SRRs calculated for each injury ICD-10 code for total injury deaths.**
**SRR****code****= SH****code****/(SH****code**** + D****code****),**
**where code=any non-excluded ICD-10 S or T code**
**SH****code**** = weighted total mentions of *****survived hospital***** for each code  **
**D****code**** = weighted total mentions of *****in-hospital *****deaths + *****pre-hospital deaths***** for each code**
**where weighted total mention = 1/number of ICD codes reported for death**
**SRRs for ICD injury codes were ranked into 6 ordinal levels of severity with roughly equal numbers of deaths in each severity level.**

**Methods to get severity ranking**

## Report to MRG

## ICD-10 Injury and poisoning codes by severity ranking

## Five leading “main” injuries selected for deaths with two or more injury diagnoses*

| Leading injury | United States |  |  |  |  |
| --- | --- | --- | --- | --- | --- |
|  | Lowest used line |  |  |  |  |
| 1 | S29.9 |  |  |  |  |
| 2 | S06.9 |  |  |  |  |
| 3 | S19.9 |  |  |  |  |
| 4 | S09.9 |  |  |  |  |
| 5 | S21.9 |  |  |  |  |
|  |  |  |  |  |  |
| Tie for highest ranked                         |  16% |  |  |  |  |

- NOTE: In both countries majority of deaths have one injury mentioned

## Five leading “main” injuries selected for deaths with two or more injury diagnoses

| Leading injury | United States |  |  |  | Sweden |
| --- | --- | --- | --- | --- | --- |
|  | Lowest used line | All |  |  |  |
| 1 | S29.9 | S06.9 |  |  |  |
| 2 | S06.9 | S29.9 |  |  |  |
| 3 | S19.9 | T14.1 |  |  |  |
| 4 | S09.9 | S09.9 |  |  |  |
| 5 | S21.9 | T07 |  |  |  |
|  |  |  |  |  |  |
| Tie for highest ranked                         |  16% | 19% |  |  |  |

- NOTE: In both countries majority of deaths have one injury mentioned

## Five leading “main” injuries selected for deaths with two or more injury diagnoses

| Leading injury | United States |  |  |  | Sweden |
| --- | --- | --- | --- | --- | --- |
|  | Lowest used line | All |  |  | All |
| 1 | S29.9 | S06.9 |  |  | S06.9 |
| 2 | S06.9 | S29.9 |  |  | T51.0 |
| 3 | S19.9 | T14.1 |  |  | T79.2 |
| 4 | S09.9 | S09.9 |  |  | S27.7 |
| 5 | S21.9 | T07 |  |  | S25.0 |
|  |  |  |  |  |  |
| Tie for highest ranked                         |  16% | 19% |  |  | 22% |

- NOTE: In both countries majority of deaths have one injury mentioned

## Selection of main injury among common pairs

- Certain injury pairs account for high proportions of deaths with two or more injuries listed.
- For MRG to review methods, a main injury was selected for common pairs of fatal injuries in the US, Australia, New Zealand, and Sweden.

## Common pairs example

| Obs | Code1 | Code2 | Main | Code 1 SRR | Code 1 rank | Code 2 SRR | Code 2 rank |
| --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | S02.9 = Fracture of skull and facial bones, part unspecified | S06.9 = Intracranial injury, unspecified | S06.9 | 0.72198 | 4 | 0.28098 | 5 |
| 2 | S02.1 = Fracture of base of skull | S06.9 = Intracranial injury, unspecified | S06.9 | 0.77487 | 3 | 0.28098 | 5 |
| 3 | S06.5 = Traumatic subdural haemorrhage | S09.9 = Unspecified injury of head | Same rank | 0.75509 | 3 | 0.72487 | 3 |

## Next steps

- MRG is reviewing the report of the Injury ICE
- ICD expert review
- Practical test on a sample of injuries
- Compare main injury selected using current (ICD-10 method) and new method suggested (incorporating severity ranking)
- ICE possible next steps:
- Ask medical experts to review empirically derived severity rankings.
- Compare severity rankings to updated ICDMAP (ICD-10 to AIS05) developed by Maria Segui-Gomez and colleagues
- 	Doing nothing is not an option for the U.S. because we would like to add a main injury indicator to the mortality file.