[Coding problems in German mortality statistics as illustrated by ischaemic heart disease].
BACKGROUND
The German mortality statistics are an important data source in terms of research and health policy but might be influenced by different sources of error such as ICD-10 coding by regional authorities. The aim of this study was to identify state-specific coding problems using the example of ischaemic heart disease (IHD) and myocardial infarction (MI).


METHODS
After obtaining age-standardised mortality rates (1998-2008), outlier analyses were used to identify German states with suspect changes in mortality from IHD or MI over time or suspect proportional mortality from an unspecific cause-of-death (ICD-10 R00-R99). Values outside the 3-fold interquartile range (IQR) from the IQR boundaries were considered as outliers. The impact of these discrepancies was studied by using an ecological correlation between state-specific poverty rates and mortality from IHD or MI as an example.


RESULTS
During the study period, mortality rates dropped by 38.1% for IHD and by 38.7% for MI. Suspect mortality trends or proportional mortality rates were identified in Berlin, Bremen, Hamburg, Schleswig-Holstein and Saarland. The association between state-specific poverty rates and mortality from IHD or MI increased after exclusion of the suspect states.


CONCLUSIONS
The ICD-10 coding by regional authorities seems to be an important source of error. A standardisation of coding procedures is urgently needed.
Andersohn
F
F
Institut für Sozialmedizin, Epidemiologie und Gesundheitsökonomie, Charité-Universitätsmedizin Berlin. frank.andersohn@charite.de
Müller-Riemenschneider
F
F
Willich
S N
SN
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002423:Cause of Death; D005260:Female; D005858:Germany; D006291:Health Policy; D006302:Health Services Research / Q000706:statistics & numerical data; D006801:Humans; D038801:International Classification of Diseases; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000401:mortality*; D017202:Myocardial Ischemia / Q000401:mortality*; D016311:Outliers, DRG; D011203:Poverty / Q000706:statistics & numerical data; D013223:Statistics as Topic