The Barell matrix
In the latest issue of Injury Prevention we were pleased to note that an editorial had been written about the Barell matrix.1 Unfortunately, the editorial gives the reader the impression that the Barell matrix is one whose two dimensions are the (1) ICD-9 CM injury diagnosis codes (often referred to as “N” codes) and the (2) ICD-9 CM external cause of injury codes (E codes). This is not the case. The Barell matrix uses the two dimensions of the diagnosis code—(1) the nature of the injury and (2) the body site of the injury—to describe injuries more completely.
Historically, users of ICD-9 CM have used only the nature of the injury (the fractures, open wounds, burns) to describe patterns of injury. The Barell matrix is useful for allowing the researcher (both the epidemiologist and the clinician) to fully characterize the injury so that demographics and health related outcomes for patients, for example, with fractures to the lower extremity can be readily distinguished from patients with fractures of the vertebral column.
The Barell matrix says nothing about E codes. In fact, there is a completely separate matrix of external cause codes that can be found under the title of “frameworks” at http://www.cdc.gov/nchs/about/otheract/ice/projects.htm.
