We use the SIemens Advia for hepatitis C IgG Ab measurements. The Advia gives a result in signal/Cutt-off ratio. However, in loinc there are only Hepatitis C IgG entries that have a property AConc. The advia does not measure a concentration. There is a LOINC code (51656-7) that describes signal/cuttoff ratio. However, signal/cuttoff is included in the component and property is ratio (relative density). Imho it would be more in line with other codes to define the property as signal/cuttoff ratio. However this property does not exist. How should we make a request to add this test to LOINC?