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The University of Virginia/Padova Type 1 Diabetes Simulator Matches the Glucose Traces of a Clinical Trial

Open access
Visentin, Roberto, Dalla Man, Chiara, Kovatchev, Boris, Cobelli, Claudio·2014·Diabetes Technology & Therapeutics

Abstract

Background: In 2008, the Food and Drug Administration (FDA) accepted our type 1 diabetes mellitus (T1DM) simulator (S2008), equipped with 100 in silico adults, 100 adolescents, and 100 children, as a substitute for preclinical trials for certain insulin treatments, including closed-loop algorithms. Hypoglycemia was well described in the simulator, but recent closed-loop trials showed a much larger frequency of hypoglycemia events in patients compared with the in silico ones. In order to better describe the distribution of glucose concentration observed in clinical trials, the simulator has recently been updated, and modifications have been accepted by the FDA (S2013). The aim of this study is to assess the validity of the S2013 simulator against clinical data and compare its performance with that of the S2008. Subjects and Methods: The database consists of 24 T1DM subjects who received dinner (70.7±3.3 g of carbohydrate) and breakfast (52.9±0.1 g of carbohydrate) in two occasions (open- and closed-loop), for a total of 96 postmeal glucose profiles. Measured plasma glucose profiles were compared with those simulated in 100 in silico adults, and the continuous glucose error grid analysis (CG-EGA) was used to assess the validity of the simulated traces. Moreover, the most common outcome metrics have been compared. Results: The frequency of hypoglycemia episodes predicted by the S2013 well reproduces that observed during clinical trials as proven by the CG-EGA. In addition, the outcome metrics provided by the S2013 are similar to those observed in clinical trials in a set of T1DM subjects. Conclusions: We demonstrated that the virtual subjects of the S2013 are representative of the T1DM population observed in a clinical trial. We conclude that the S2013 is a valid tool usable to test the robustness of closed-loop control algorithms for artificial pancreas.

Overview

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TL;DR

The updated UVA/Padova type 1 diabetes simulator S2013 was assessed against clinical glucose data from 24 adults and compared with the earlier S2008. S2013 reproduced clinical glucose traces and hypoglycemia better, supporting its use for in silico testing of closed-loop algorithms.

Key findings

  • CG-EGA accurate+benign percentages were 86.4% in hypoglycemia, 99.9% in euglycemia, and 99.2% in hyperglycemia for S2013, versus 40.7%, 99.8%, and 99.5% for S2008.
  • S2013 outcome metrics were substantially similar to clinical data except for percentage of time in hypoglycemia (6.22±11.81 vs 4.04±7.93; P=0.006) and hypoglycemia area under the curve (5.00±14.50 vs 2.65±8.99 mg·h/dL; P=0.019); most S2008 metrics were significantly lower than clinical values (P<0.05).
  • Hypoglycemia events numbered 37 in data, 32 with S2013, and 19 with S2008; hyperglycemia events were 72, 67, and 61, respectively.
  • Real versus virtual parameter differences averaged 18% for body weight and 67% for carbohydrate ratio; a >50% carbohydrate-ratio difference occurred in 23 subjects, and 14 of them would have benefited from a ratio closer to the virtual one. No subject was matched by the same virtual patient at both dinner and breakfast.

Methods

  • The clinical database included 24 T1DM adults from Virginia (n=11), Padova (n=7), and Montpellier (n=6), each studied during two 22-h admissions (open- and closed-loop), with dinner (70.7±3.3 g carbohydrate) and breakfast (52.9±0.1 g carbohydrate), yielding 96 postmeal traces plus 8 overnight portions with at least one hypoglycemic episode.
  • Each measured plasma glucose profile was compared with 100 in silico adults undergoing the same meals, basal insulin, and boluses; the best FIT-matched simulated profile was evaluated by continuous glucose error grid analysis (CG-EGA).
  • Outcome metrics were compared between clinical and simulated data using paired t tests or Wilcoxon signed rank tests, with significance at P=0.05; S2013 includes modified hypoglycemia glucose kinetics via the Low BG Risk Index, a glucagon counterregulation model, and refined virtual-subject generation.

Limitations

  • Stated by the authors: the 24-subject dataset is not large despite 96 traces; only inpatient data were used, so outpatient free-living robustness is unproven; only adults were considered; the model does not yet account for intraindividual diurnal parameter variability; and glucagon secretion may not be appropriate for all long-duration T1DM patients.
  • Evident from the text: the protocol did not include a physical activity session, so simulator validity under exercise is not tested.

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Integrity signals

Registry

Crossref · 10.1089/dia.2013.0377

Cites

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  • It may state two separate claims as one. 8
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  • The paper relies on this without support.

    The virtual subjects well span the variability of the T1DM population observed in vivo.

    “The virtual subjects well span the variability of the T1DM population observed in vivo.”
  • The paper relies on this without support.

    Recent closed-loop trials showed a much larger frequency of hypoglycemia events in patients compared with the in silico ones.

    “Hypoglycemia was well described in the simulator, but recent closed-loop trials showed a much larger frequency of hypoglycemia events in patients compared with the in silico ones.”
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Research works printed but not linked: 1

  1. Micheletto F, , Dalla Man C, , Vella A, , Cobelli C: A model of glucagon secretion and action in healthy subjects [abstract A105]. In: Book of Abstracts. 10th Diabetes Technology Meeting. Bethesda, MD: Diabetes Technology Society, 2010.

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Metadata

Authors
Visentin, R., Dalla Man, C., Kovatchev, B., & Cobelli, C.
Affiliations
  • University of Padua (IT)
  • University of Padova
  • University of Virginia (US)
Corresponding author
Cobelli, Claudio
Venue
Diabetes Technology & Therapeutics
Published
2014-07
Volume
16
Issue
7
Pages
428-434
ISSN
  • 1520-9156 (ISSN-L)
  • 1557-8593
OpenAlex
W2322662949
Cited by
103
References
11
Citations by year
2026: 7 · 2025: 8 · 2024: 7 · 2023: 12 · 2022: 6 · 2021: 9 · 2020: 9 · 2019: 9 · 2018: 12 · 2017: 15 · 2016: 6 · 2015: 1 · 2014: 2
FWCI
6.44
Type
journal article
Language
en
Open access
Locations
  • Diabetes Technology & Therapeutics (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
  • Padua Research Archive (University of Padova) (submittedVersion, other-oa)
Topics
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Diabetes Management and Research
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Diabetes Treatment and Management
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Diabetes and associated disorders
Keywords
type 1 diabetes, artificial pancreas, hypoglycemia, glucose profile, postprandial blood glucose
MeSH terms
Adolescent, Adult, Algorithms, Blood Glucose, Clinical Trials as Topic, Computer Simulation, Diabetes Mellitus, Type 1, Female, Humans, Hypoglycemia, Hypoglycemic Agents, Insulin, Insulin Infusion Systems, Male, United States, Blood Glucose Self-Monitoring, Reproducibility of Results

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