Primary device
CGM
Continuous glucose monitoring
Study duration
12–24 mo
Compliance must be sustained
Key risk
Sensor gap
Miss replacement → data lost
Metabolic Compliance Model
CGM · Weight · Diary · Real-time QC
Continuous glucose monitoring is described as a passive data collection technology — the sensor does the work, the patient just wears it. In clinical trial practice, this underestimates the compliance management required.
CGM sensors have finite lifespans — typically 7 to 14 days depending on the device — and must be replaced on a consistent schedule. Each sensor replacement is an opportunity for user error: incorrect application site, inadequate adhesion, failure to initialize the new sensor, or simply forgetting to replace it when the previous one expires. In a 12-month study, each patient performs roughly 30 to 50 sensor replacements. Each one is a potential compliance event.
Add to this the sync requirements between sensor and reader or smartphone, dietary and activity protocol compliance, ePRO completion, and weight measurement scheduling — and the total compliance burden in a diabetes or obesity trial is substantial. Managing it requires systematic monitoring and proactive support, not just enrollment and access to devices.
See also: Diabetes & Obesity Trials · Wearables & Digital Endpoints
Sensor replacement gaps are the most common source of CGM data loss. Proactive reminders timed to the sensor expiry window — 24 to 48 hours before expiration, not after — prevent the four-to-seven-day gaps that result from a forgotten replacement.
Placement on the wrong body site, insufficient skin prep, or poor adhesion causes early sensor failure and degraded glucose readings. Onboarding training and periodic technique checks reduce this error rate across the study period.
CGM sensors generate continuous data but depend on regular reader or smartphone sync to transmit it. Sync failures create data gaps that don't affect the patient's experience of the device — making them easy to miss without active monitoring.
Weight endpoints in obesity trials require measurements under controlled conditions — same time of day, same pre-measurement protocol. Measurements taken at variable times or under different conditions introduce confounders that reduce endpoint validity.
Food intake diaries in metabolic trials have high burden and typically high non-compliance in the middle and late phases of long studies. Proactive monitoring and outreach before the decline becomes entrenched is the most effective intervention.
A patient enrolled in a two-year metabolic study at month 18 is a very different participant than at month one. Long-term retention requires mid-study re-engagement campaigns and sustained support infrastructure — not just strong onboarding.
Common devices include Abbott FreeStyle Libre, Dexcom G6/G7, and Medtronic Guardian. Device selection depends on glucose measurement frequency requirements, sensor lifespan, data transmission format, and regulatory context. Research-grade configurations may differ from consumer versions.
No. Some trials use intermittent glucose measurements, HbA1c at defined intervals, or other metabolic markers as primary endpoints. CGM is most valuable when the endpoint requires characterizing glucose variability, time-in-range metrics, or continuous glucose profiles rather than point-in-time measurements.
Time-in-range (TIR) is typically defined as the percentage of time CGM readings fall within a target glucose range (commonly 70–180 mg/dL for type 2 diabetes). TIR analysis requires a minimum CGM data completeness threshold — typically 70% of expected readings — below which the metric is not considered reliable.
Delve provides CGM compliance monitoring, weight endpoint support, ePRO integration, and concierge follow-up for metabolic studies — protecting data quality across the full arc of long-duration programs.
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