OGTT at Home Using CGM vs at the Clinic (OGTT-CGM)

Oral Glucose Tolerance Test at Home With Continuous Glucose Monitoring vs Standard Clinic-based Testing

This randomized, crossover study evaluates the feasibility and accuracy of a self-administered oral glucose tolerance test (OGTT) at home using continuous glucose monitoring (CGM) compared to a standard clinic-based OGTT. Participants with prediabetes will undergo both home-based and clinic-based OGTTs, with glucose levels measured via CGM and venous plasma glucose. The primary outcome is the correlation between CGM-based glucose values and standard OGTT results. Secondary outcomes include diagnostic agreement, metabolic hormone associations, and feasibility of home-based testing as a diagnostic tool for dysglycemia.

Study Overview

• Status: Recruiting
• Conditions: Diabetes; Pre-diabetes
• Intervention / Treatment: Diagnostic test: OGTT at home using CGM; Diagnostic test: OGTT at the clinic

Detailed Description

This study aims to evaluate the feasibility, accuracy, and diagnostic utility of a self-administered oral glucose tolerance test (OGTT) at home using continuous glucose monitoring (CGM) compared to a standard clinic-based OGTT.

Study Design Type: Randomized, crossover study Participants: 75 adults with prediabetes Intervention: Each participant will complete both a home-based OGTT with CGM and a clinic-based OGTT with venous plasma glucose measurement.

Primary Objective To assess the correlation between glucose values obtained from a CGM-based home OGTT and a standard venous OGTT performed in the clinic.

Secondary Objectives Evaluate diagnostic agreement between CGM-derived and venous glucose measurements.

Assess variability in glucose responses between the two methods. Investigate associations between OGTT results and metabolic/sex hormones. Determine feasibility and patient adherence to home-based testing.

Methods Participants will be randomized into two groups: one starting with a clinic-based OGTT, the other with a home-based OGTT, followed by a crossover period. CGM will continuously monitor glucose responses, and standard venous plasma glucose measurements will serve as the reference method.

Clinical Relevance A validated home-based OGTT using CGM could improve access to glucose tolerance testing, reduce patient burden, and enhance early detection of dysglycemia.

• Study Type: Interventional
• Enrollment (Estimated): 75
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Peder af Geijerstam, MD, PhD; Phone Number: +46739597426; Email: peder.af.geijerstam@liu.se

Study Locations

• Sweden
  • Jönköping County
    • Huskvarna, Jönköping County, Sweden, 55185
      • Recruiting
      • Primary Health Care Center Bra Liv Rosenhälsan
      • Contact: Maria Samefors, MD, PhD; Phone Number: +46102423550; Email: maria.samefors@liu.se
  • Norrköping
    • Norrköping, Norrköping, Sweden, 60239
      • Recruiting
      • Primary Health Care Center Cityhälsan Centrum
      • Contact: Peder af Geijerstam, MD, PhD; Phone Number: +46101059140; Email: peder.af.geijerstam@liu.se
  • Östergötland County
    • Linköping, Östergötland County, Sweden, 58662
      • Recruiting
      • Primary Care Center Vårdcentralen Kärna
      • Contact: Karin Rådholm, MD, PhD; Phone Number: +4613281756; Email: karin.radholm@liu.se

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Prediabetes indicated by ≥2 of the following values, measured at separate occasions or through different analyses during the past 2 years:
• - Fasting venous plasma glucose ≥6.1 but ≤6.9 mmol/L
• - Non-fasting venous plasma glucose ≥7.8 but ≤11.0 mmol/L
• - HbA1c ≥39 but ≤47 mmol/mol
• Access to a smart phone which is compatible with the CGM application and has working Bluetooth connectivity
• Ability to read and respond to online instructions and questionnaires in Swedish.

Exclusion Criteria:

• T2D indicated by ≥2 of the following values, measured at different occasions or through different analyses:
• - Fasting venous plasma glucose ≥7.0 mmol/L
• - Non-fasting venous plasma glucose value ≥11.1 mmol/L
• - HbA1c ≥48 mmol/mol
• Previous bariatric surgery e.g., gastric by-pass or gastric sleeve surgery
• Body mass index <20 kg/m2
• Body weight <43 kg
• Current pregnancy
• Need of regular use of GLP-1 receptor agonists, SGLT-2 inhibitors, acetaminophen or ascorbic acid supplements during the study period
• Fear of needle sticks
• Shift work during the study period
• Involvement in the study design, data collection, analysis, or participant recruitment.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Diagnostic
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: OGTT at the clinic then at home	Diagnostic test: OGTT at home using CGM; OGTT at home using CGM; Other Names: OGTT-home; Diagnostic test: OGTT at the clinic; OGTT at the clinic; Other Names: OGTT-clinic
Experimental: OGTT at home then at the clinic	Diagnostic test: OGTT at home using CGM; OGTT at home using CGM; Other Names: OGTT-home; Diagnostic test: OGTT at the clinic; OGTT at the clinic; Other Names: OGTT-clinic

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Diagnostic accuracy of the 2-hour CGM glucose value during home-based OGTT compared with 2-hour venous plasma glucose during clinic-based OGTT	The diagnostic accuracy of the 2-hour interstitial glucose measured by CGM during a home-based oral glucose tolerance test (OGTT) will be evaluated against the 2-hour venous plasma glucose obtained during a clinic-based OGTT (reference standard) for the classification of normoglycemia, prediabetes, and diabetes. The 2-hour CGM value will be defined as the first CGM recording at or within 5 minutes after the 2-hour timepoint (i.e., between 120 and 125 minutes). Diagnostic accuracy will be assessed using sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and Cohen's kappa coefficient for overall classification agreement, each reported with 95% CIs. Systematic bias and limits of agreement between the two continuous glucose measurements will further be assessed using Bland-Altman analysis.	2 hours after the start of the OGTT

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Diagnostic accuracy of the lag-adjusted 2-hour CGM glucose value during home-based OGTT compared with 2-hour venous plasma glucose during clinic-based OGTT	The diagnostic accuracy of a lag-adjusted CGM glucose value during a home-based oral glucose tolerance test (OGTT) will be evaluated against the 2-hour venous plasma glucose during a clinic-based OGTT (reference standard) for the classification of normoglycemia, prediabetes, and diabetes. The lag-adjusted timepoint will be identified from the clinic-based OGTT as the CGM recording between 120 and 140 minutes showing the highest concordance with the 2-hour venous plasma glucose, assessed using Lin's concordance correlation coefficient (CCC), and applied accordingly during the home-based OGTT. Diagnostic accuracy will be assessed using sensitivity, specificity, PPV, NPV, and Cohen's kappa, each with 95% CIs, and Bland-Altman analysis will be used to assess systematic bias and limits of agreement.	0-20 minutes after the 2-hour timepoint of the OGTT (lag-adjusted)
Reproducibility of home-based OGTT using CGM	Reproducibility of the 2-hour CGM glucose value across the two home-based OGTTs will be assessed using intraclass correlation coefficients (ICC), and agreement in glycemic classification (normoglycemia, prediabetes, and diabetes) will be assessed using weighted Cohen's kappa. Both the unadjusted and lag-adjusted 2-hour CGM values will be evaluated.	2 hours and 2 hours plus 0-20 minutes lag-adjustment after the start of the OGTT

Collaborators and Investigators

• Sponsor: Linkoeping University
• Collaborators: Region Östergötland; Region Jönköping County
• Investigators: Principal Investigator: Peder af Geijerstam, MD, PhD, Linkoeping University

Study record dates

Study Major Dates

• Study Start (Actual): June 11, 2025
• Primary Completion (Estimated): May 31, 2026
• Study Completion (Estimated): December 31, 2040

Study Registration Dates

• First Submitted: March 1, 2025
• First Submitted That Met QC Criteria: March 1, 2025
• First Posted (Actual): March 6, 2025

Study Record Updates

• Last Update Posted (Actual): May 19, 2026
• Last Update Submitted That Met QC Criteria: May 15, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Diabetes; Glucose; Continuous glucose monitoring; Oral glucose tolerance test; Pre-diabetes
• Additional Relevant MeSH Terms: Endocrine System Diseases; Metabolic Diseases; Glucose Metabolism Disorders; Hyperglycemia; Nutritional and Metabolic Diseases; Diabetes Mellitus; Glucose Intolerance
• Other Study ID Numbers: ogtt_cgm

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED
• IPD Plan Description: If suitable according to ethical guidelines.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No