In 2019, the Danish National Patient Register was updated, making it no longer possible to directly determine whether a hospital contact concerned an inpatient or an outpatient. To address this challenge, the Data Powerhouse developed an algorithm capable of classifying patient types. Additionally, we are part of a collaborative group aiming to establish national consensus in this area.

​​Publications

Data-Driven Algorithms for Classification of In- and Outpatients in the Danish National Patient Register. Buchardt AS, Madsen P, Jensen A (2025) 

With the introduction of the latest version of the Danish National Patient Register (DNPR3) in 2019, it was no longer possible for researchers to identify whether a hospital contact concerned an inpatient or an outpatient (the so-called patient type). This study aimed to develop and evaluate algorithms that can categorize a hospital contact as either an admission, an elective outpatient visit, or an emergency outpatient visit (the latter previously known as emergency room visits). The goal was to promote consensus in data interpretation among researchers using Danish health registers. 

The study showed that both methods based on departments as well as those using information about the individual hospital contact (e.g., duration and overnight stay), including hybrid approaches that combine both levels, could effectively categorize patient types. The choice of the best approach depends, among other factors, on whether a study has access to data at the department level and whether the study covers both the period before and after the introduction of DNPR3.​​​
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