Injury MICA - Variable Definitions

Record Selection for All Injuries

The injuries in this MICA are those recorded by hospitals for their emergency room patients and inpatients, as reported by the Missouri Department of Health and Senior Services Patient Abstract System (PAS).

The causes of the injuries are defined according to the external-cause codes (E codes) of the International Classification of Diseases-9th Revision-Clinical Modification (ICD-9-CM). This coding system is used by hospitals to record the injuries and diseases of their patients. Below are the E-codes and diagnoses that are used to define injury causes and determine whether a patient’s records should be included in this MICA.

Records were selected for this MICA if there was a diagnosis code of 800-995 in the first diagnosis field and the injury was not a late effect according to either the principal diagnosis (905-909) code or the E-code (929,959,969,989,999). Medical misadventures (E870-E879) and adverse effects of drugs (E930-E949) were also excluded. Not all causes of injury are available for display in the MICA. The particular causes that can be displayed were chosen based on their frequency of occurrence and their interest to the public health community.

Injury Matrix

This MICA is structured to follow the Intent-by-Mechanism matrix recommended by the Centers for Disease Control. The matrix categorizes all E-codes according to a mechanism of injury (firearm, poison, etc.) and four intentions: 1) assault: intent to injure others; 2) self-injury: intent to injure oneself; 3) unintentional: accidental or no intent to hurt anyone, and 4)intent undetermined: intention cannot be determined). For example, firearms can be used with the intent of injuring oneself or others or they can injure people unintentionally. If specific mechanisms are selected for display in a table, the user should understand that the mechanisms will encompass all intentions (unless an intention is selected as a qualifying variable for the table.)

Special Problems

Abusive Behavior

Abusive behavior, a type of assaultive behavior, does not fit very well into the intention-mechanism structure. Ideally, abusive behavior, like the other intentions, could be categorized by which mechanism was used--striking someone, cutting someone, etc.--but the E-codes are not structured this way, and abuse can only be categorized by the types of abusive behavior--spouse abuse, child abuse, etc.

A further complication with the Abuse/Neglect/Rape category is that a record may fall into more than one category of abuse depending on the patient's age and the E-codes and diagnosis codes on the record. For example, some records had both an E-code for spouse abuse and a diagnosis code for sexual abuse. Records with multiple codes were categorized according to the following priority: spouse abuse, sexual abuse, rape, shaken baby, physical abuse, neglect.

Motor Vehicle Crashes

E-coding of injuries due to motor vehicle crashes is also somewhat confusing. Crashes are grouped by E-codes into motor vehicle crashes on a trafficway (E-codes 810-819), nontrafficway motor vehicle crashes, such as in a parking lot or driveway (E-codes 820-825), and nonmotorized road vehicle crashes, such as those involving bicycles or animals being ridden (E-codes 826-829), which can travel on a trafficway or nontrafficway. Within each of these groups the E-codes identify the injured person, as in motor vehicle driver, bicycle driver, pedestrian, etc. Within the nonmotorized road vehicle category, the two injured groups of most interest are pedestrians and bicycle drivers. Four non-traffic motor vehicle intermediate items and two nonmotor vehicle intermediate items: Bicyclist-nontraffic, Pedestrian-nontraffic, Other Vehicle-nontraffic, Motorcyclist-nontraffic, Other Person-nontraffic, Pedestrian-nonmotor vehicle, and Bicyclist-nonmotor vehicle. Thus the Bicyclist-nontraffic and Pedestrian-nontraffic intermediate groups would include bikers and pedestrians injured by ATV's, for example; the Pedestrian-nonmotor vehicle and Bicyclist-nonmotor vehicle intermediate groups would include bike riders and pedestrians not injured by motor vehicles, as with a person who is injured by hitting his/ her head on the road after falling off a bike. A third group of injured bicyclists and pedestrians are those who are hit by motor vehicles on a trafficway, and their totals are given by looking at the intermediate items in the Motor Vehicle Trafficway category.

Multiple Records

The inpatient records and emergency room records are designed to be mutually exclusive in the PAS system. If a person is admitted to the hospital through the emergency room, the inpatient record but not the E/R record should be included in the PAS. Only if the person is treated in the E/R and released should the E/R record be included in the PAS. Due to the size of this data system and the resulting editing challenge it represents, a small number of patients will have both an E/R and inpatient record for the same hospital stay. Additionally, patients who return to the hospital for follow-up treatment will also have more than one E/R or inpatient record for an injury episode. The number of injury records is thus somewhat more numerous than the number of injury episodes and patients. An attempt to separate records from persons indicated that the number of patients was 10 percent less than the number of records for the combined E/R and inpatient records. This percent was fairly similar across mechanisms and intents; the largest difference in the number of patients and the number of records among mechanisms was 13% for overexertion, while the largest difference for intentions was 16% for Unknown intent. (These percents should be considered estimates, since a small number of records do not have patient name on them, and because it is impossible to determine whether a person who has two or more records with the same E-code has been treated for separate injury incidents or has visited hospital(s) multiple times for the same injury incident.)

Injury E-Codes

Following are the ICD-9-CM E-codes and diagnosis codes used to define the causes of injury. For more detail on these categories, consult a current ICD-9-CM manual or contact us.

Intent E-codes

• Unintentional '800'-'949'
• Assault '960'-'969'
• Legal Intervention and War ‘970-979’,'990'-'999'
• Self-Injury '950'-'959'
• Unknown ‘980’-‘989’

Mechanism E-codes