## 3 Results
### Evaluation  
The evaluation happened on two levels. In the first step, we generated quantifiable results by determining how many _Properties_ were able to be mapped to a base unit representation. For this purpose, we calculated the mapping coverage we were able to achieve compared to all quantitative _Properties_. In order to estimate how thorough the coverage for real-world data would be, we matched our mappings against the Top 2000 US, Top 2000 SI and Top 300 documents, which are intended to aid users in mapping their laboratory identifiers to commonly used LOINC codes. In the second step, data on LUMA itself were gathered with five participants of the LADR laboratory network in Germany via a video conference and a subsequent discussion. Additionally, a questionnaire concerning UCUM and previous mapping efforts was handed to the participants. In terms of raw numbers, the current 210 LOINC _Properties_ in Version 2.72 can be categorized as follows for the purpose of this project:* Thirty-four did not belong to the quantitative subset. * Of the remaining one hundred and seventy-six _Properties_:
* One hundred and fifty-nine were mapped with confidence;
* Three were excluded based on ambiguous usage;
* Ten were excluded based on specifying ranges, dates or time via annotations, effectively serving no purpose within Ucum;
* Four were excluded based on being deprecated, their use being discouraged or not existing in the LOINC data set without any further clues on how they may be represented. Even when excluding 17 _Properties_ from the overall result, we managed to achieve a coverage of roughly 90% for the quantitative subset. When encountering inconsistencies in the way example units were used, we weighted keywords and descriptions in the LOINC guide highest, seeing as their usage was more coherent across all entries, especially if the example units were obviously inappropriate. For the three _Properties_ we excluded based on their ambiguous usage, we were not able to reconcile the inconsistencies. They include \"Fluid Conductance\", \"Fluid Resistance\" and \"Resistance\". \"Fluid Conductance\" is currently used to measure fluid conductivity, electrical conductivity and diffusion capac  
Figure 6: The left side of the mapping window deals with the user’s instance data while the right one is based on the formalization we postulated. ity. \"Fluid Resistance\" is currently used to measure airway resistance and _specific_ airway resistance. \"Resistance\" is currently used for measuring hemodynamic resistance and impedance. Although formulating a base unit representation for each of these use cases by themselves is not an issue, they are incompatible when assuming that _Properties_ should be unambiguous. In order to simplify the uptake of mapping proprietary laboratory codings to LOINC, two data sets are provided on the official LOINC web presence. Each contains roughly 2000 LOINC codes that are supposed to cover 98% of use cases for typical lab result volumes. The data were gathered from three large organizations by the Regenstrief Institute and the data sets are split into a US and an SI version. The US version is intended for users who favor reporting in mass units, whereas the SI set favors molar units. In addition to these internationally provided data sets, Germany's Medical Informatics Initiative (MII) has produced a similar effort for national adoption and mapping guidance. As mentioned before, a set of 300 general laboratory test scenarios was envisioned to cover the most clinically relevant use cases. As a basis, LOINC-coded analyses were collected from five university laboratories in Germany and ranked according to their frequency of usage [22; 28]. Based on their principal characteristics--mainly the analyte in the Component axis (e.g., glucose) and the specimen in the System axis (e.g., blood)--these codes were aggregated into the aforementioned 300 groups. For each group, one primary LOINC code was chosen that represents the respective test scenario in the most general or common way.