Reliability of coding causes of death with ICD-10 in Germany

The international classification of diseases (ICD) is used to code death worldwide uniformly and comparably. This study investigates the reliability of national ICD-10 coding practice by assessing agreement of two official coding offices in Germany. Inter-observer agreement for coding of 372 quasi-randomly selected death certificates is measured by percentages of agreement and simple kappa coefficients. Only 209 (56%) deaths were coded with the same 3-digit ICD-10 code. Agreement of the main chapters according to ICD-10 is higher with 78.2% and a kappa statistic of 0.69 (CI 95%, 0.63-0.75). Examples show that the coding rules correctly applied to the information given on the death certificates may lead to different conclusions. Data show good agreement in the marginal distribution, and thus population frequencies of causes of death may be more reliable despite limited agreement between the two coding offices.