[Diagnosis Coding in German Medical Practices: A Retrospective Study Using Routine Data].

OBJECTIVES: Primary care physicians and specialists deal with a wide range of diseases. The diagnoses are coded by using the annual version of the International Statistical Classification of Diseases and Related Health Problems, 10th revised version, German modification (ICD-10-GM). The aim of this study was to describe the current spectrum of documented diagnoses by physicians. Based on the underlying conditions, a broad variety of ICD-10-GM codes could be expected, which in many cases would not be coded to the final character (terminal).

METHODS: 22,287,583 data sets of 900 medical practices of 13 various physician groups were included in this retrospective study. The data originate from the regions Brandenburg and North Rhine and the accounting period October 2014 - September 2015. The normalized Gini coefficient was applied as a measure for inequality.

RESULTS: 97.6 % of the total data set were coded to the final character using the ICD-10-GM. ENT physicians used the highest rate of terminal codes (99.6 %), whereas orthopedists and cardiologists used the lowest rate (94.0 %). The broadest variety of different ICD-10-GM codes was used by primary care physicians (71.1 % of all possible terminal codes), the smallest variety was used by ophthalmologists (22.9 %). The lowest inequality of using ICD-10-GM codes could be detected for primary care physicians (Gini coefficient: 0.56), the highest inequality could be shown for ophthalmologists (Gini coefficient: 0.93).

CONCLUSIONS: The specialists mainly use a circumscribed set of ICD-10-GM codes, whereas primary care physicians not only use a broad variety of different ICD-10-GM codes, but very often code them to their final character. This indicates a high quality of coding.