Reliability of ICD-10 external cause of death codes in the National Coroners Information System

Availability of ICD-10 cause of death codes in the National Coroners Information System (NCIS) strengthens its value as a public health surveillance tool. This study quantified the completeness of external cause ICD-10 codes in the NCIS for Victorian deaths (as assigned by the Australian Bureau of Statistics (ABS) in the yearly Cause of Death data). It also examined the concordance between external cause ICD-10 codes contained in the NCIS and a re-code of the same deaths conducted by an independent coder. Of 7,400 NCIS external cause deaths included in this study, 961 (13.0%) did not contain an ABS assigned ICD-10 code and 225 (3.0%) contained only a natural cause code. Where an ABS assigned external cause ICD-10 code was present (n=6,214), 4,397 (70.8%) matched exactly with the independently assigned ICD-10 code. Coding disparity primarily related to differences in assignment of intent and specificity. However, in a small number of deaths (n=49, 0.8%) there was coding disparity for both intent and external cause category. NCIS users should be aware of the limitations of relying only on ICD-10 codes contained within the NCIS for deaths prior to 2007 and consider using these in combination with the other NCIS data fields and code sets to ensure optimum case identification.