SP.718 Special Topics at Edgerton Center: D-Lab Health: Medical Technologies for the Developing World

Transcription

1 MIT OpenCourseWare SP.718 Special Topics at Edgerton Center: D-Lab Health: Medical Technologies for the Developing World Spring 2009 For information about citing these materials or our Terms of Use, visit:

2 Colorimetric Diagnostic Assay for the Measurement of Blood Glucose Deepali Ravel, Yi Wang, and anonymous students AL, ML and DR Dlab Health 1

3 Background 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 National Prevalence 7.6% (2007) 9.4% (2025) Courtesy of the International Diabetes Federation. Used with permission. Nicaragua Diabetes Statistics: Deaths Attributable Males 10.4% (2007) Females 18.2% (2007) Prevalence of Diabetes in Central America 2

4 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 mg/dl Poor glycemic control 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. 3

5 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 4

6 Diabetes Prevalence in 2007 Courtesy of the International Diabetes Federation. Used with permission. 5

7 Diabetes Prevalence in 2025 Courtesy of the International Diabetes Federation. Used with permission. 6

8 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 7

9 Current Glucometers Drop a prick of blood onto a test strip, which the glucometer than reads to measure glucose levels, through an electrochemical assay. Source: Wikipedia (public domain) 8

10 Design Specifications Characteristic Current Our Prototype Sample Volume 0.3ul to 10ul 10ul Accuracy 10-15% Unknown Range Be able to measure healthy glucose range: mg/dl mg/dl Processing Time 3-60 seconds seconds Testing Site Mostly fingertips Fingertip Testing Frequency Up to times per day Same Reader Size Around 8cm x 5cm x 3cm (palm size) 20cm x 6cm x 2.5cm Reader Price $25 to $100. Some companies offer free monitors, but sell test strips Very low Test Strip Price $1.00-$2.00 <$0.20 Units US preference is mg/dl. Canada and Europe preference is mmol/l (x/18) mg/dl Other Qualities Allow data storage/ monitoring None 9

11 Design Ideas I: Telemedicine A. Use Camera Phone to take image of test strip B. Transfer image to computer in offsite 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 10

12 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 Image remove due to copyright restrictions. Photos of the GlucoPhone, from 11

13 Pugh Chart Design Goals Status Quo Design 1 Design 2 Design 3 Design 4 Current Microfluidic Current Paper glucometers are glucose test Glucometer with diagnostic- only expensive and system non-proprietary colorimetric proprietary. strips strip- no meter Design Parameters Weights (1-3) New, Local Glucometer with Locally Built Test Strips Long-term Effectiveness Speed of Use Reliability Accuracy Economy Accessibility Usability Simplicity Practicality Maintainability Aesthetic Appeal Environmental Friendliness Safety Versatility Efficiency Marketability Ease of Integration Total Weighted Total

14 Pugh Chart Design Goals Weights (1-3) Status Quo Design 1 Design 2 Design 3 Design 4 Current Microfluidic Current Paper New, Local glucometers are glucose test Glucometer with diagnostic- only Glucometer with expensive and proprietary. system non-proprietary strips colorimetric strip- no meter Locally Built Test Strips Long-term Effectiveness Reliability Accuracy Economy Maintainability Safety Total Weighted Total

15 Our Proposed Solution: Colorimetric Strips The reagents for the glucose assay are placed on a Filter Paper Test Strip. 10ul of the glucose solution (blood) are deposited on strip. Color change from clear to blue is witnessed. 14

16 Our Proposed Solution: Reader Battery-operated hand-held reader LEDs indicate blood glucose-level within set ranges 15

17 Costs Paper Test Strips: Reagents per strip : 1.5 cents Packaging: 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. 16

18 Testing and Validation 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 17

19 Testing and Validation 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 18

20 Manufacturing and Regulatory Pathways 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 19

21 Medical Device Compass Chart Lab-Intensive Glucose Assay Effectiveness Our Current Prototype Urinanalysis Strips Our Goal Colorimetric Test Strips Standard Glucometer Glucophone Advanced Glucometer 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. Cost 20

22 Future Work 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. 21

23 Questions? 22