Cited by 105Diabetes Management and ResearchDiabetes Treatment and ManagementDiabetes and associated disorders

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.

AI snapshot

Written from the paper’s full text.

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.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1089/dia.2013.0377

Cites

11 of 11 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 7 cited sources checked · 0 supported · 0 flagged

  • Findingown data
    § Discussion

    A difference between real and virtual CR >50% was present in 23 subjects.

    “This analysis revealed that a difference between real and virtual CR >50% was present in 23 subjects.”
    Quote in the paperNot a substantial claim
  • Findingown data
    § Results

    S2008 CG-EGA performance was similar to S2013 in euglycemia and hyperglycemia (99.8% and 99.5% accurate+benign).

    “The results of the S2008 (Table 1, second row) show that the performance is similar to that of S2013 in euglycemia and hyperglycemia (percentage in accurate+benign zones: 99.8% in euglycemia and 99.5% in hyperglycemia) but worse in hypoglycemia (percentage in accurate+benign zones: 40.7%).”
    Quote in the paperSubstantial claim
  • Findingown data
    § Abstract

    The frequency of hypoglycemia episodes predicted by S2013 well reproduces that observed during clinical trials, as proven by CG-EGA.

    “The frequency of hypoglycemia episodes predicted by the S2013 well reproduces that observed during clinical trials as proven by the CG-EGA.”
    • Also stated in: § Discussion · boosted
      “where the hypoglycemic episodes predicted by the simulator well reflect those observed in clinical trials (Fig. 2, left panel).”
    Quote in the paperSubstantial claim
  • Findingown data
    § Results

    S2013 well reproduces glucose patterns observed in clinical trials in all clinical zones, including rapid falls in glucose and hypoglycemic episodes.

    “The S2013 well reproduces the glucose patterns observed in clinical trials in all clinical zones, in particular the rapid falls in glucose level and the hypoglycemic episodes.”
    • Also stated in: § Discussion · boosted
      “Our results show that the S2013 well reproduces the glucose patterns in eu-, hyper-, and, above all, hypoglycemia, where the hypoglycemic episodes predicted by the simulator well reflect those observed in clinical trials (Fig. 2, left panel).”
    Quote in the paperSubstantial claim
  • Findingown data
    § Results

    For S2008, most outcome metrics are significantly lower in simulation than clinical data (P<0.05).

    “For the S2008 (Table 2, third column), most of the outcome metrics are significantly lower in simulation (P<0.05).”
    • Also stated in: § Discussion · plain
      “Moreover, most of the in silico outcome metrics are significantly different from their clinical counterparts (Table 2, third column).”
    Quote in the paperSubstantial claim
  • May combine two claims. 8
  • Classified as probably not a substantial claim. 6
  • May combine two claims.

    Findingown data
    § Results

    S2013 CG-EGA accurate+benign percentages were 86.4% in hypoglycemia, 99.9% in euglycemia, and 99.2% in hyperglycemia.

    “The average results of CG-EGA of the S2013 (Table 1, first row) are very good in hypo-, eu-, and hyperglycemia (percentage in accurate+benign zones: 86.4% in hypoglycemia, 99.9% in euglycemia and 99.2% in hyperglycemia).”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Findingown data
    § Discussion

    The percentage difference between subject and virtual parameters was 18% on average for body weight and 67% for CR.

    “We found that the percentage difference between subject and virtual parameters was 18% on average for body weight and 67% for CR.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Findingown data
    § Discussion

    When matching was limited to virtual subjects with CR similar to the real one, a match was always found except for eight traces, which presented hypoglycemia and thus had suboptimal CR.

    “In this case a match was always found except for eight traces, which, however, presented hypoglycemia, and thus the corresponding CR were suboptimal, as explained above.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Findingown data
    § Results

    S2008 simulated profiles reproduce data well in euglycemia and hyperglycemia but not hypoglycemic episodes.

    “The simulated profiles obtained with the S2008 reproduce quite well the data in euglycemia and hyperglycemia but not the hypoglycemic episodes.”
    • Also stated in: § Discussion · plain
      “On the other hand, we observed that the S2008 reproduces quite well the glucose patterns in euglycemia and hyperglycemia, but not the hypoglycemic episodes, which are difficult to predict (Fig. 2, right panel).”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Findingown data
    § Results

    S2013 outcome metrics are substantially similar to clinical data, except percentage of time in hypoglycemia and area under the BG curve for hypoglycemia.

    “The outcome metrics of S2013 simulations (Table 2, second column) are substantially similar to those obtained from the data, except for the percentage of time in hypoglycemia and the area under the BG curve for hypoglycemia.”
    • Also stated in: § Abstract · plain
      “In addition, the outcome metrics provided by the S2013 are similar to those observed in clinical trials in a set of T1DM subjects.”
    Quote in the paperSubstantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given
    § Discussion

    The S2013 model does not yet take into account intraindividual diurnal parameter variability.

    “The most important one is that the model does not yet take into account the intraindividual diurnal parameter variability.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Study design and conductown data
    § Discussion

    The dataset used for model assessment only includes inpatient data, and there are no data to prove that performance would be as robust in outpatient free-living individuals.

    “Second, the dataset used for model assessment only includes inpatient data. Unfortunately, we do not have data to prove that the performance would be as robust in outpatient free-living individuals.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Premisecitation
    § Introduction

    S2008 was successfully validated against data from T1DM subjects, reproducing distribution of insulin correction factors, glucose traces in children, and glucose traces of induced moderate hypoglycemia in adults.

    “The simulator was successfully validated against data of different experiments performed in T1DM subjects, reproducing (1) distribution of insulin correction factors in the T1DM population of children and adults, (2) glucose traces in children with T1DM, and (3) glucose traces of induced moderate hypoglycemia observed in adults in clinical trials at the University of Virginia.1”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [1] Kovatchev BP, Breton M, Dalla Man C, Cobelli C: In silico preclinical trials: a proof of concept in closed-loop control of type 1 diabetes. J Diabetes Sci Technol 2009;3:44–55 [DOI] [PMC free article] [PubMed] [Google Scholar] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given
    § Discussion

    Only the adult population has been considered in this article.

    “Third, only the adult population has been considered in this article.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Interpretationown data
    § Discussion

    The simulator is not designed to do prospective studies on a given individual, given the large intrasubject variability of real life.

    “However, it is important to stress that the simulator is not designed to do prospective studies on a given individual, given the large intrasubject variability of real life.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [3] Hinshaw L, Dalla Man C, Nandy DK, Saad A, Bharucha AE, Levine JA, Rizza RA, Basu R, Carter RE, Cobelli C, Kudva YC, Basu A: Diurnal pattern of insulin action in type 1 diabetes: implications for a closed loop system. Diabetes 2013;62:2223–2229 [DOI] [PMC free article] [PubMed] [Google Scholar] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given
    § Discussion

    The dataset used for assessment, consisting of 24 subjects and 96 traces, cannot be considered a large database.

    “First, the dataset used for the assessment, consisting of 24 subjects, cannot be considered a large database, despite subjects being studied twice with two meals per trial for a total of 96 traces.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given
    § Discussion

    If information on the exact timing of meals and carbohydrate content is available, the method proposed here can be applied to outpatient free-living individuals.

    “In principle, if information on the exact timing of the meals and carbohydrates content is available, we are pretty confident that the method proposed here can be applied to outpatient free-living individuals.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given
    § Introduction

    The database used for model assessment was not used for the update of S2013.

    “This database was not used for the update of S2013.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given
    § Discussion

    Finding a match between real and simulated subjects is likely easier if only three or four BG values are available in a day, as happens in real life.

    “However, it is likely that finding a match between real and simulated subjects is easier if only three or four BG values are available in a day, as happens in real life.”
    Quote in the paperNot a substantial claim
14 of 14
  • 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.”
2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • The UVA/Padova T1D simulator consists of a fully identified maximal model of glucose metabolism in T1D and a virtual population of 100 adult PwDs displaying key metabolic behaviors observed in the general population of individuals with T1D.

    “we used the University of Virginia (UVA)/Padova T1D simulator, which consists of a fully identified maximal model of glucose metabolism in T1D 18 and a virtual population of 100 adult PwDs displaying key metabolic behaviors observed in the general population of individuals with T1D.[18][19][20][21]”

    From Time to Moderate and Severe Hyperglycemia and Ketonemia Following an Insulin Pump Occlusion (2024) · cites this paper as [20]

    The Subjects and Methods passage describes a glucose–insulin model and 100 virtual adults, and the Discussion says the updated virtual population represents the T1D population observed in clinical trials. Our copy does not describe the model as “fully identified” or “maximal,” and its evidence for population representativeness is framed around clinical-trial observations rather than the general T1D population. (LLM, conf=0.87)

    Experimental — accuracy not yet measured
  • Visentin et al. [7] found that the S2013 simulator overestimated percent time spent in hypoglycemia significantly.

    “unlike the S2008 simulator, the S2013 simulator overestimated the percent time spent in hypoglycemia significantly [7].”

Cites

Flagged first, then by citations

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.

Cited by

Sorted by citations

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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