The ICD-10 injury diagnosis matrix: Grouping S and T codes by body region and nature of injury. Paul R. Jones and Bruce A. Lawrence Pacific Institute for Research and Evaluation Lois A. Fingerhut National Center for Health Statistics November, 2004. Background.
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Paul R. Jones and Bruce A. Lawrence
Pacific Institute for Research and Evaluation
Lois A. Fingerhut
National Center for Health Statistics
In order to validate the algorithm, we first tested it against the ICD-10 coded Multiple Cause of Death (MCOD) data for 2000.
For records containing an injury diagnosis (i.e., an S or T code), we selected the injury diagnosis from the entity axis assigned by the death certificate as the earliest injury diagnosisin the chain of causes leading to death.
We ran this classifying diagnosis (Dx0) through our algorithm. The algorithm successfully assigned nature-of-injury and body-region codes to each case.
For every injury death, we applied the algorithm to each injury diagnosis on the record axis (except superficial injuries, which were judged to be unlikely to cause death).
In order to avoid double counting deaths with multiple injury diagnoses, we gave each diagnosis a weight equal to the reciprocal of the number of injury diagnoses on the record.
Example: a death that involved a head fracture and a crushed thorax would be counted as half a death from head fracture and half a death from crushed thorax.
By diagnosis matrix cell, we then computed the weighted numbers of cases across all injury deaths.
Other External Effects19.1%
Note. 1 = E.g., asphyxiation, drowning.
Note. 1 = E.g., foreign body, poisoning, external effects.
Fractures of the hip were especially prevalent among women over 50, accounting for 22.1% of all injury-related deaths - the highest ranking category for this demographic group. For men over 50, hip fractures accounted for 10.2% of injury deaths. For people under 50, however, hip fracture deaths were almost nonexistent.
Foreign body in the trunk accounted for 15.7% of all injury deaths of people over 50, but only 1.7% for those 50 or under. These are mostly choking deaths.
Internal injuries of the head (brain injuries) accounted for 8.1% of injury deaths of people over 50, but only 3.7% for ages 50 and under.
Among people age 50 or less, the biggest fatal injury category was poisoning, which, together with toxic effects, accounted for 20.3% of all injury deaths. Poisoning and toxic effects were more prevalent among women (25.0%) than among men (18.8%). They were less common among people over 50 (7.4%).
Other external effects (mostly drowning and asphyxiation) accounted for 12.2% of injury deaths among those 50 or under, but only 5.6% among those over 50.
Unspecified injuries of multiple regions accounted for 10.7% of injury deaths among those 50 or less, but only 5.9% among those over 50.
Other fatal injury categories were more common among people 50 and under (continued):
Unspecified head injuries accounted for 10.1% of injury deaths among those 50 or less, but only 6.6% among those over 50.
Open wounds were more common among males than females. Open wounds of the head accounted for 10.0% of injury deaths among men and 3.4% among women. Open wounds of the thorax accounted for 3.5% of injury deaths among men and 1.2% among women.
5.4% of injury death certificates lacked any injury diagnoses. Some coroners and MEs follow the convention (which is permitted by coding rules) of letting a cause code represent the injury without any accompanying injury diagnosis code.
Of the cases with at least one injury diagnosis code (the sub-sample used elsewhere in this study),
70.3% had a single injury diagnosis
19.6% had two injury diagnoses
6.4% had three injury diagnoses, and
3.6% had four or more injury diagnoses.
Internal organ injuries of the head (i.e., brain injuries) and unspecified injuries of the thorax were especially likely to be accompanied by at least one other injury diagnosis (51.1% and 56.5%, respectively).
This exercise gave a clearer picture of a known weakness of ICD-10 coded data - the heavy reliance on “multiple” and “unspecified” categories that are of little use to researchers.
In our injury-codeddata, 31.5% of deaths with injury diagnoses have a multiple or unspecified code for either the nature of injury or the body region, and 13.6% have both.
The algorithm proved robust against a large mortality dataset that could reasonably be expected to provide a sufficient test, but it should be validated against other datasets before being widely circulated.
The heavy use of “multiple” and “unspecified” diagnoses will be a challenge to those using these ICD-10 coded data for injury research.