MIT OpenCourseWare · 2019. 9. 13. · Test Strips Urinanalysis Strips. Our Goal . Colorimetric...
Transcript of MIT OpenCourseWare · 2019. 9. 13. · Test Strips Urinanalysis Strips. Our Goal . Colorimetric...
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SP.718 Special Topics at Edgerton Center: D-Lab Health: Medical Technologies for the Developing WorldSpring 2009
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Colorimetric Diagnostic Assay for the Measurement of Blood Glucose
Dlab
Health
1
Deepali Ravel, Yi Wang, and anonymous students AL, ML and DR
Background
Prevalence of Diabetes in Central America
•
One glucometer
is shared
between 15 clinics in the
Nicaraguan province of Estelí.
•
Test strips are proprietary and
expensive
•
Poor distribution of test strips
and glucometers
–
leads to a
mismatch in supply at hospitals
Deaths AttributableMales –
10.4% (2007)
Females –
18.2% (2007)
Nicaragua Diabetes Statistics:National Prevalence
7.6% (2007)9.4% (2025)
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Courtesy of the International Diabetes Federation. Used with permission.
Diabetes Management
•
When a patient has diabetes, their body cannot effectively regulate glucose levels.
•
It is dangerous if glucose concentrations fall outside normal range
•
Goal: Glycemic
control
–
Keep within normal values of 70-130 mg/dl
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Poor glycemic
control –
200-500 mg/dl over months
•
Measure blood glucose levels 4 –
5 times a day
–
Allow patients to act quickly to correct for swings in their glucose concentrations, by either injecting a dose of insulin or consuming glucose pills.
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Diabetes in the Developing World
Why is it a problem?
•
Has reached epidemic proportions-
Due to rapid cultural changes, increasing urbanization, dietary
changes
•
Currently affects 246 million people, 6% of world’s adult population-
Contributes to 19.7 million DALYs-
By 2025, 80% of all new cases will appear in developing countries
•
6 million people develop diabetes each year-
Less than half the people with diabetes in developing countries
are diagnosed
•
Diabetes causes 3.5 million deaths each year-
Two-thirds of deaths caused by diabetes occur in developing countries
The burden of the disease increasingly falls on developing countries
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Diabetes Prevalence in 2007
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Courtesy of the International Diabetes Federation. Used with permission.
Diabetes Prevalence in 2025
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Courtesy of the International Diabetes Federation. Used with permission.
Problem Statement
“In order to control their disease, diabetes patients must monitor their blood glucose level on a regular basis. In the region of Estelí, in Nicaragua , one glucometer
is shared between 15 clinics, meaning that the vast majority of patients are not receiving daily monitoring. Glucose testing is so infrequent
because test strips are proprietary and expensive.
Our challenge is to design a fast, cheap, safe and reliable way of measuring glucose levels that can be used widely by diabetes patients, even in poor resource settings.”
-
Team GlucoTank
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Current Glucometers
Drop a prick of blood onto a test strip, which the
glucometer
than reads to measure glucose levels,
through an electrochemical assay.
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Source: Wikipedia (public domain)
Design SpecificationsCharacteristic Current Our PrototypeSample Volume 0.3ul to 10ul 10ul
Accuracy 10-15% UnknownRange Be able to measure healthy glucose
range: 70-130 mg/dl100-200 mg/dl
Processing Time 3-60 seconds 30-60 seconds
Testing Site Mostly fingertips FingertipTesting Frequency Up to 10-12 times per day SameReader Size Around 8cm x 5cm x 3cm (palm size) 20cm x 6cm x 2.5cmReader Price $25 to $100. Some companies offer free
monitors, but sell test stripsVery low
Test Strip Price $1.00-$2.00 <$0.20Units US preference is mg/dl. Canada and
Europe preference is mmol/l
(x/18)mg/dl
Other Qualities Allow data storage/ monitoring None
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Design Ideas I: Telemedicine
A. Use Camera Phone to take image of test strip
B. Transfer image to computer in off-
site lab/hospital
C. Use imaging software such as Photoshop to convert image to grayscale
D. Read out the mean intensity and use “key”
to translate value to Glucose level
•
Create colorimetric test strips, and a phone (or computer) application that, when a picture of the strip is loaded, it converts it to gray scale and measures the average light intensity-
translating that to a glucose level. • However:
-
Cell phones that have computer power to do this are quite expensive (idea not able to adapt to single user level)-
Similar idea being pursued by Diagnostics for All
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Design Ideas II: Glucophone
•
More expensive technology than the telemedicine idea.
•
Uses cell phone to display, power, and store data–
Data can be sent to a central database for remote patient monitoring
•
However: –
Expensive to develop
–
Technologically challenging?–
Company already doing this
–
Would be difficult designing component attachable to all phones
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Image remove due to copyright restrictions.
Photos of the GlucoPhone, from http://www.glucophone.com.
Pugh ChartDesign Goals Status Quo Design 1 Design 2 Design 3 Design 4
DesignParameters
Weights (1-3)
Current glucometers
are expensive and
proprietary.
Microfluidic
glucose test system
Current Glucometer
with non-proprietary
strips
Paper diagnostic-
only colorimetric
strip-
no meter
New, Local Glucometer
with Locally Built Test
Strips
Long-term Effectiveness 3 -1 1 -1 1 1Speed of Use 2 1 1 1 1 1Reliability 3 1 1 1 -1 1Accuracy 3 1 0 1 -1 1Economy 3 0 -1 1 1 1Accessibility 2 1 1 1 1 1Usability 2 1 0 1 1 1Simplicity 2 1 0 1 1 1Practicality 2 0 0 1 1 1Maintainability 3 0 1 0 1 1Aesthetic Appeal 1 1 1 1 1 -1Environmental Friendliness 1 0 1 0 1 0Safety 3 1 1 1 1 1Versatility 2 1 1 1 1 0Efficiency 2 1 1 1 1 1Marketability 2 0 0 -1 1 1Ease of Integration 1 0 1 0 1 1Total 9 10 10 13 13Weighted Total 19 20 22 25 32
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Pugh Chart
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Design Goals Weights (1-3) Status Quo Design 1 Design 2 Design 3 Design 4 Current
glucometers
are expensive and
proprietary.
Microfluidic
glucose test system
Current Glucometer
with non-proprietary
strips
Paper diagnostic-
only colorimetric
strip-
no meter
New, Local Glucometer
with Locally Built Test
Strips
Long-term Effectiveness 3 -1 1 -1 1 1
Reliability 3 1 1 1 -1 1Accuracy 3 1 0 1 -1 1Economy 3 0 -1 1 1 1
Maintainability 3 0 1 0 1 1
Safety 3 1 1 1 1 1
Total 2 3 3 2 6Weighted Total 6 9 9 6 18
Our Proposed Solution: Colorimetric Strips
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The reagents for theglucose assay are placedon a Filter Paper Test Strip.10ul of the glucose solution(blood) are deposited onstrip. Color change fromclear to blue is witnessed.
Our Proposed Solution: Reader
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Battery-operated hand-held readerLEDs
indicate blood glucose-level within set ranges
Costs
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Paper Test Strips: Reagents per strip : 1.5 centsPackaging: approximately 5 cents per strip -Packaging constraints: must protect the strips from light, since some reagents are light-sensitive. Solution: use aluminum coated paper.
Reader: Approximately $10 or less per reader-
Cost of electrical components is very low.
Testing and Validation
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Test strips: Tested different concentrations of glucose
• Fasting levels, normal levels, and high levels all give different dye intensity.
•Tested different reagent deposition orders
Future work: test time/light sensitivity of reagents, inkjet printing of reagents
Testing and Validation
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Reader:
•
Tested device with “calibration strips”
and our strips
-
Sensitive to white and three increasing intensities of blue on calibration strips
•
Tested device in normal room lighting and within device housing (dark) Future work: Test device with specific glucose concentrations, actual strips and
smaller ranges of concentration
Manufacturing and Regulatory Pathways
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Our design is simple and cheap to produce:• Local diagnostic company• Local materials
Distribution:Follow the distribution system currently used in Nicaragua, and spread to Polyclinics.3-4 for use in clinic at first, but eventually 1 glucometer
per
Diabetes patient. Regulation:
• 510(k) pathway• Predicate device-
colorimetric glucose assay, optic technology
Medical Device Compass Chart
Glucophone
Cost
Effe
ctiv
enes
s
Standard Glucometer
Advanced Glucometer
Lab-Intensive Glucose Assay
Colorimetric Test Strips
Urinanalysis
Strips
Our Goal
Colorimetric test strips were abandoned around 10 years ago for the electrochemical test strips, since there was no appropriate reader at that time. The electrochemical assay is more expensive, but also more accurate.
Our Current
Prototype
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Future Work
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Developing the Test Strip:
•
Double layer strip idea, with a top layer that is able to filter
the blood cells allowing just the serum to pass through to reagents.
Developing the Reader:
•
Creating a more sensitive reader with more LED indicator lights, so we can inform of patients their glucose levels more accurately.
Questions?
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