# Presentation: 497040

## ICD-9 to ICD-10 Comparability:

- Lois A. Fingerhut, MA and Margaret Warner, PhD
- Special Projects Branch, Office of Analysis and Epidemiology

**ICD-9 to ICD-10 Comparability:**
**Applicability to Injury Data**

## Overview

- Process of developing ICD-10 codes for external cause matrix
- Comparability ratio
- Percent agreement
- Application of comparability ratio
- Comparability for multiple cause diagnosis data

## Development of Comparability based on External Cause (EC) of Injury Matrix

- Development of ICD-10 EC matrix
- Compare ICD-9 to ICD-10 code by code for underlying cause of death
- Some movement of codes in ICD-9 matrix based on changes to ICD-10 (e.g. MVT) and updates (e.g. drowning)
- Validate with comparability ratios
- For trends, ICD-9 EC matrix adjusted to match ICD-10 EC matrix

## Final Comparability Ratios by Intent

- All injury 		1.0159
- Unintentional  	1.0251
- Suicide 			1.0022
- Homicide 		1.0020
- Undetermined 	0.9867
- Legal interv/war 	0.9235

## Effect of Final Comparability Ratios by Intent on 1998 death rates

**	****	****	****	**_CR__	__      CDR     CMR_
- All injury 		1.0159 * 53.3=54.1
- Unintentional 	1.0251 *34.2= 35.1
- Suicide 			1.0022 * 11.1=11.1
- Homicide 		1.0020 * 6.5=   6.5
- Undetermined 	0.9867 * 1.4=   1.3
- Legal interv/war 	0.9235 * 0.1=   0.1

- CR- comparability ratio, CDR- crude death rate, CMR- comparability modified rate

## Effect of Final Comparability Ratios by Mechanism on 1998 death rates

**	****	****	**_CR__	__      CDR     CMR_
- MVT	 	.9545 * 15.3=14.6
- Firearm   	1.0012 *11.1=11.1
- Poisoning	1.0192 * 6.7=6.8
- Fall		1.0015 * 4.8= 4.8
- Suffocation	1.0974 *4.0=  4.4

## Comparability ratios for external causes of injury with the “worst” ratios

## Transportation-related injuries

- Not 1-to-1 match for many codes
- Often no comparable ICD-10 codes
- Almost 20% of all ICD-9 MVT deaths
- Comparability ratios
- All transport			0 .9930
- Other land transport	2.6350
- Pedal cyclist, MVT          0.8038
- Pedal cyclist, other	1.7477

## Other summary measures

- Comparability ratio summarizes net effect
- Percent agreement between ICD-9 and ICD-10
- Inflows – in ICD-10 but not ICD-9
- Outflows – in ICD-9 but not ICD-10
- Coded to both

## Example: Suffocation 

- Total ICD-9   = 9,888
- Total ICD-10 = 10,851
- CR = 1.0974  (10 % more in 10 than in 9)
- Agreement      			9,716	88 %
- Outflows (ICD-9 & not ICD-10)    172		2 %
- Inflows (ICD-10 & not ICD-9)	1,135 	10 %

## Example: Suffocation 

- Inflows to suffocation (n=1,135)
- From Natural Causes	780   69%
- 	Pneumonia			208	18%     Residual disease		189	17% Pneumonitis			124	11%
- From External Causes	355   31%

## Multiple cause of death comparability issues for injury diagnoses

- No precedent exists, no standard cause of death lists for injury diagnoses
- Entity vs Record axis codes
- All mentions vs any mention of an injury
- ICD-9 and ICD-10 have opposite axes for injury diagnoses
- ICD-9 by nature of injury (fractures, open wounds..)
- ICD-10 by body region of injury

## Multiple cause of death comparability issues for injury diagnoses

- Need a standard format to compare ICD-9 and ICD-10 diagnosis or nature of injury codes
- A revised Barell Matrix is needed
- Current version uses ICD-9 CM injury diagnosis codes
- ICD-9 CM codes have 4th and 5th digits
- Most mortality codes have only 3 digits
- Comparability issues are abundant...

## Amputations....

- ICD-9 codes applied only to upper and lower limbs
- ICD-10 codes are far more extensive also covering thorax, head, neck, trunk, multiple body regions
- 				                    _CR      % agreement_
- 	All Amputations                    2.26     27%
-    Matching ‘limb’ codes           0.85     58%

## Slide 15

| Nature of injury | Comparability
ratio | Percent 
agreement |
| --- | --- | --- |
| All ‘nature of injury’ (w/o comp. care) | 0.999 | 99.5 |
| Fractures | 0.970 | 93.9 |
| Poisoning | 0.999
 | 98.2 |
| Upper  and lower extremities | ??? Much more detail in ICD-10!
 | ??
 |

## Conclusions

- Important to consider comparability
- Large differences in transportation codes
- Trends: Basic recommendations
- If at all possible, do not combine across revisions
- Apply CR to 1998 data only
- On web in near future-- Death and death rates for ICD-9 comparability modified EC matrix by age and sex
- How to deal with nature of injury codes—work in progress

## Questions/Comments Lois FingerhutLFingerhut@cdc.govorMargaret WarnerMWarner@cdc.gov