The Usability of the Minimal Model as used with the Intravenous Glucose Tolerance Test

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Modelling in Diabetes The Insulin Sensitivity
Module
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The Usability of the Minimal Model as used with
the Intravenous Glucose Tolerance Test

• Richard Hayes, Bill Grimson, Giovanni Pacini,
  John Nolan

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Introduction

• Context of Work (Medilink)
• Use of Minimal Model to measure Insulin
  Sensitivity from the IVGTT
• Usability Issues
• A User Interface
• Integration Issues

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Focus of Presentation

• Usability of the application
• Non-transportable Non windows
• Typically run offline by expert modeller
• Integration of the application into EHCR
  environment
• Transportable, windows GUI
• Ease of use by clinician, less user intervention

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MEDILINK
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Insulin Sensitivity from the IVGTT

• Insulin Sensitivity is an important indicator for
  the extent to which a patient is suffering from
  Type II Diabetes
• It is a single number which is estimated from the
  data generated by the IVGTT
• It is used in research rather than clinical
  applications

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I V G T T
mM
glucose
140
insulin
120
nM
Measured Insulin
100
glucose sampling
80
60
insulin
40
20
0
20
40
60
80
100
120
140
160
180
time
min
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The Minimal Model
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Compartmental Model for Insulin and Glucose
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Glucose / Insulin Kinetics
Insulin Degradation
Plasma Insulin
Remote Insulin
reduce
increase
Plasma Glucose
Peripheral Tissue
LIVER
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Minimal Model Equations
G(t) plasma glucose concentration (Gb
basal) I(t) plasma Insulin concentration (Ib
basal) X(t) remote insulin concentration p1
SG Glucose effectiveness index p3//p2 SI
Insulin sensitivity index
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Estimate the Parameters
300
Measured Glucose
Measured Insulin
250
Modelled Glucose
200
150
100
50
0
20
40
60
80
100
120
140
160
180
200
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Relationship between Minimal Model and parameter
estimator
Minimal Model
Plasma Insulin

Simulated Glucose
p
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m
o
t
e

P
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I
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D
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n

3

I
n
s
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i
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I
n
s
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l
i
n

Parameter Initial Conditions
P
2

r
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d
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e

i
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a
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e

P
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P
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p
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a
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L
I
V
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R

T
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s
u
e

G
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S

p

g
1
Parameter Estimator
Adjust parameters until best match is achieved
Compare Simulated Glucose and measured Plasma
Glucose
Parameter Vector
Plasma Glucose
SI
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Use of MINMOD
Query Result Accuracy Precision of estimates
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A User Interface
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Expert User vs New User

3

User 1
2.5


U/ml))
2

m
/(

AR

1
-
1.5

FM

Insulin Sensitivity(min
1

PP

0.5

DN

0

0

0.5

1

1.5

2

2.5

3

User 2
-
1
m
Insulin Sensitivity (min
/(
U/ml))


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Integration of Insulin Sensitivity Measurement

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Automatic vs. User driven
Si Automatically
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4.5
4
3.5
3
2.5
2
1.5
1
0.5

0
0
0.5
1
1.5
2
2.5
3
3.5
4
Si from GUI/USER
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Automatic vs. User driven
Si Automatically
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5

0
0
0.5
1
1.5
2
2.5
3
3.5
4
Si from GUI/USER
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Automatic vs. User driven
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Conclusions

• An important Computer application (data analysis
  for research) with significant USABILITY
  difficulties
• Investigated user requirements
• Designed a user interface
• Integrated it with a Patient Record Server
• Medilink an Active Record

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