- Design
- Prospective observational validation study
- Population
- 58 adults with diabetes undergoing surgery or ICU admission
- Primary outcome
- Median absolute relative difference versus point-of-care glucose
- Effect
- MARD 10.9%; 98% in Clarke zones A/B; +4.5 points during hypoperfusion
Continuous glucose monitors are now common in outpatients with diabetes, and many arrive for surgery wearing one. A prospective BJA validation study compared a current-generation CGM sensor with point-of-care glucose testing in 58 people with diabetes on glucose-lowering treatment undergoing surgery or ICU admission (mean age 71).
Median absolute relative difference was 10.9%, and 98% of 1,212 paired readings fell in clinically acceptable zones of the Clarke error grid. The mean difference was −1 mmol/L, but limits of agreement were wide (−5.6 to 3.4 mmol/L). During hypoperfusion — mean arterial pressure below 65, vasopressor infusion or low perfusion index — the error rose by 4.5 percentage points. No hypoglycaemia occurred, so accuracy in the range that matters most was not tested.
CGM can help with trend monitoring, but point-of-care confirmation remains necessary for treatment decisions, especially in shocked patients.
- Patients arriving with a CGM can keep it on as a trend monitor during surgery or ICU stay.
- Confirm any reading that will change treatment with a point-of-care or laboratory glucose.
- Treat CGM readings with extra caution during hypotension, vasopressor use or poor peripheral perfusion.
- Accuracy during hypoglycaemia was not tested in this study.
Why it matters
Sensors already worn by patients could reduce finger-prick testing, but not in the patients where accuracy is worst.
Don't overread it
With no hypoglycaemic readings and 58 patients, the study cannot show CGM is safe for detecting low glucose in hospital.
The statistics, in plain English
A median error of about 11% is acceptable for trends. Limits of agreement of −5.6 to 3.4 mmol/L mean individual readings can be several units off.
Read the rest in the app
You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.
Scan to keep reading on your phone. No account needed to start.
Tomorrow morning, before your first patient
One edition a day for anaesthesiology, written by the desk, every claim tied to its paper. Six minutes.
Get the app — free