Blood Glucose: Plasma vs Interstitial Fluid. Call for a new LOINC Code!

With LabResults the blood glucose is measured in the plasma. For this the LOINC code 14749-6 is used. This code can also be used for at home testing by patients.

With the new Glucose monitoring devices like Dexcom G4 / G5 or Abbott FreeStyle Libre and others a new LOINC classification code of the resulting blood glucose is necessary. This is because these devices do not measure in the plasma but in the interstitial fluid - usually in the upper skin layer.

The new LOINC code I am proposing should allow to differentiate between measurements in plasma and interstitial fluid. This is important for quality analysis. It is also important because dosing decisions for insulin should only be derived from blood glucose measured in the blood plasma. So this differentiation is important for clinical settings as well.

Best regards,
Holger Schmeken

It appears the new code ended up being 97507-8 “Average glucose [Mass/volume] in Interstitial fluid during Reporting Period” in release 2.70, June 2021. “The average glucose value over a period of time and typically reported from a continuous glucose monitor (CGM) device.”