Exploring determinants and regional variation of diagnostic imaging utilization rates in German inpatient care

Introduction: Germany ranks high concerning the per capita supply of computer tomographs (CT) and positron emission tomographs (PET) which may incentivize supply-induced use. Beyond that, international comparison shows high per capita examinations. However, misuse of diagnostic imaging may cause harm to patients and the health care system. The use of diagnostic imaging in Germany has been insufficiently studied so far. Therefore, the study aimed to determine the extent of regional differences as well as supply and demand side factors of per capita CT and PET examinations in German inpatient care.Methods: Cartographic visualizations and a random intercept model controlling for the regional disease bur-den, ambulatory provided supply and demand, and population deprivation between 2010 and 2017 for CT and between 2016 and 2017 for PET were applied. For this purpose, the Nationwide hospital discharge data (DRG statistics), hospital structured quality reports, the National Association of Statutory Health Insurance Physicians, the Central Research Institute of Ambulatory Health Care in Germany, and the German Index of Socioeconomic Deprivation were used.Results: We found a substantial regional variation of examination rates (-63 to +108 % for CT and from -94 up to +847 % for PET). Regarding PET, the supply structures have a significant impact on examinations per 1,000 inhabitants (28.46, p < .000). Both devices were used in correlation with the regional disease bur-den. Ambulatory and inpatient CT examination rates were positively associated.Discussion: The regional differences identified are to some extent attributable to the regional burden of dis-ease and thus warranted. Although the inpatient PET supply influences utilization rates, the direction of the effect should be investigated more closely for valid statements. The findings in terms of CT should be treated with caution. The cartographic distribution and examination rates indicate global overuse. The clear separa-tion of inpatient and ambulatory sectors leads to misallocation of scarce resources, medically unnecessary multiple examinations, and capacity utilization problems.Conclusion: The results obtained have great potential for assessing and analyzing the adoption and rapid expansion of imaging technologies. Capacity utilization figures should be the focus of further research to assess utilization rates both economically and medically. Policy makers should address ongoing issues of operational and organizational separation of inpatient and ambulatory sectors in the German health care system.