Centers for Disease Control and Prevention Multiple cause of injury data: Selecting a main injury Margaret Warner, Ph.D. Injury ICE meeting Mexico 2005

Overview International differences in multiple cause data Methods to analyze multiple cause data Selecting a main injury from MCOD Looking at commonly co-occurring injuries

Multiple cause data for injury deaths United States External cause of injury Underlying cause *U,V,W,X,Y codes Intent and cause Injury diagnoses S and T codes Body region and nature Other diagnoses A,B,C…R codes Up to 20 conditions mentioned on death certificate including …

Difference in multiple cause data Do not code multiple cause of death Canada Code all causes, do not select main injury United States Code all causes and select a main injury England & Wales Code only a main injury ???

USA 1.53 * (1999) Sweeden ( ) Scotland ( ) England & Wales Multiple injuries listed per death Average number of injury codes 1 Percent of deaths by number of injuries coded 23 or more ( ) * 1.74 if duplicate codes included

Multiple injury deaths Many methods to analyze. For example: Total mentions of injury diagnoses Any mention (i.e. at least one mention) Weighted total mention – weight = 1/total number of injuries per death Main injury or first listed injury

Number of Mentions: ‘Total’, ‘Any’ & ‘Weighted total’ by body region US, 2002 Body region

Why select main injury? Data issues May differ by certifier Artifacts of coding rules ICD international and some countries only collect the main injury…

If select main injury, is information lost? Is one injury more important than the other??? Rules can be established about priority, but what conclusions will be drawn from data Are there combinations of injuries which are more deadly?

ICD and selecting a main injury ICD-10 Vol. II, Section ICD-9Precedence list –most “severe” ICD-10 Selects the initiating condition (similar to external cause) Asked for input from the Mortality reference group (MRG) MRG (1) decides on applications and interpretation of the ICD to mortality and (2) recommends updates to ICD

Selecting a main injury: Recommendations from MRG 1) Eliminate trivial injuries and superficial injuries from consideration 2) If obvious causal sequence, select injury which led to death 3) Select from among remaining injuries using severity ranking (e.g. Precedence list) 4) Select first mentioned if several at same level of severity

Analyze data by common pairs of injuries To determine if certain combinations commonly occur together (e.g. head and thorax injuries) If yes, Computer algorithms could be adapted to choose for these deaths Should a single code by used to identify combination?

Common pairs, US, ,078 deaths with external underlying cause 1 injury listed65% of deaths 2 injuries22% 3 injuries8% injuries4% Examined unique pairs – Two nature of injury codes were treated as a unique pair regardless of the order in data

Common pairs TRUE !!!! Certain injury pairs account for high proportion of deaths with two or more injuries listed

Common pairs, results Most frequent pair – occurs 3,327 times S06.9 (Intracranial injury, unspecified) and S09.9 (Unspecified injury of the head) Second most frequent – occurs 2,671 times S09.9 (Open wound of head, part unspecified) and S29.9 (Unspecified injury of the thorax)

Expert review of 139 pairs Member of MRG and expert ICD coder Selected main injury for 83% (116 out 139) Main injury selected for 54% of deaths with 2 injuries listed

Unspecifieds Many injuries are unspecified either by body region or by nature Totally non-specific ICD codes T14.8 = Other injuries of unspecified body region T14.9 =Injury, unspecified

For 2 injuries listed Pair with …Percent distribution T14.8 (Other injury unspecified … ) 2.6 % T14.9 (Injury, unspecified) 8.4 % Superficial injuries 1.1 % Selected by expert review (116) 54.0 % Total: Main injury selected for 64.0 %

Conclusion Multiple cause data vary by country Number of injuries reported and coded Range: 0, 1, 20 Some select main injury, others keep all Many methods to analyze (total, weighted total) Selecting main injury (ICD rules might be modified)