Homework Week 1: Introduction to FDA
Accuracy and Precision
Sensitivity and Specificity
BME 489 Medical Instrumentation
Name _________Sohini_Ghosal_________________
Type your solution and upload it to Canvas as a .pdf.
FDA (Food and Drug Administration) Market Approval:
FDA approval is needed for all drugs and medical devices sold in the US. The key function of
the FDA is to ensure safety for the US population. FDA approval has implications on the
design and the time to market of your products. Note if you work with medical devices and
violate FDA regulations the product line and or company can be shut down in 24 hours if the
company / product is in violation. Many companies have full departments dedicated to ensure
products comply with FDA regulations.
Answer the following question by going to the web url:
http://www.fda.gov/cdrh/devadvice/index.html
1. What is the FDA definition of a medical device?
Answer: According to the FDA, a medical device is any device or accessory, that is intended
for the use of diagnosing or curing a condition, or affect the structure or function of the body,
and does not achieve it’s intended use through chemical action within or on the body.
2. How many class categories exist for medical devices and what class does your device
(sphygmomanometer) belong to?
Answer: There are 3 class categories that exist, class 1 being a device that is low risk, class 2
a device that is of moderate risk and finally class3 which is a device that poses high risk. While
I could not find the definite title of a sphygmomanometer, I instead found a device in the FDA
database called the antimicrobial blood pressure cuff. This device belongs to the class 2
category.
3. What is the regulation number of your device (the Sphygmomanometer)?
Answer: The regulation number on the antimicrobial blood pressure cuff is 870.1120.
4. Define what is a premarket notification (510K) and what is a PMA (premarket approval)
Answer: A premarket notification(510k) is an FDA submission pathway which shows that the
device about to be marketed is safe and effective despite its class category, and that it is
legally like the predicate that is already out in the market. A premarket approval (PMA) is
another FDA submission pathway, which demonstrates that the device about to be marketed
poses a significant risk and the user and there are not suitable predicates that exist in the
current market.
5. Would you need to file a 510K or a PMA to attain FDA approval for your device (the
Sphygmomanometer)? Why?
Answer: For the antimicrobial blood pressure cuff, you would need to file for a 510(k) since it is
a class 2 device and according to class 2 devices should already have a suitable predicate out
in the market. Because it is not a class 3 device, meaning it is not of high risk, it should be
relatively safe and effective for its end user.
6. Briefly describe one other device that has recently attained FDA approval.
Answer: A recent FDA approved device is the MiniMed 770G System, a new continuous
glucose monitoring system. This device monitors glucose levels for up to 7 days and has a
pump that delivers insulin to the user.
7. What is the difference between verification and validation to the FDA?
Answer: Verification is the process is to make sure that the device in and of itself is functional
and meets the specified requirements, usually accomplished through tests and case analyses.
Validation is the process of making sure that the correct device was constructed for the
problem is it is trying to fix and that at the end it is the right device to meet user requirements.
8. Questions on Accuracy and Precision
You are designing a new tonometer (instrument that measures eye pressure
noninvasively) to measure intraocular pressure (eye pressure). Using your device, you
record the following pressures on 1 patient with glaucoma and get the following results
where all readings are in mmHg
20
19
25
30
32
24
36
35
43
40
22
31
36
43
34
47
41
22
23
19
You are comparing your instrument to the clinical gold standard, the Goldmann
tonometer, where measuring the intraocular pressure on the same subjects under the
same conditions you obtain the following readings where all readings are in mmHg:
24
24
22
20
23
24
22
20
21
22
24
21
22
23
20
22
21
22
23
22
Part 8 A: Using MATLAB (or equivalen) calculate the mean, standard deviation and
variance of each instrument? Hint type in ‘help mean’, ‘help std’, and ‘help var’ to
Parameter
Mean
Standard Deviation
Varience
Your Tonometer
31.1
8.72
76.09
Gold Standard
22.1
1.3
1.69
Part 8 B: What are the equations for Mean, standard deviation and variance?
Answer: Mean = sum(Xi/n)
Standard deviation = sum((Xi – mean)2/n)
variance = (std)2
Part 8 C: Discuss the accuracy and precision of your tonometer compared to the clinical
gold standard.
Answer: Because my tonometer results have a larger standard deviation to the Gold standard,
my tonometer results have bad precision. My Tonometer is also less accurate to the golden
standard.
Part 8 D: Why are precision and accuracy important to the FDA? Must quote at least
two internet citations of how precision and / or accuracy has an impact in healthy care
and instrumentation design.
Hint: Do an internet search on FDA & precision and then FDA & accuracy.
Answer: Accuracy is important to the FDA due to an incident in 2007 when assay
reproducibility became difficult to do because of inaccurate concentration results from the
original and repeated results of various testing.
https://www.qualitydigest.com/inside/fda-compliance-article/defining-accuracy-andprecision.html
Precision is important ot the FDA as they have developed a section called Precision Medicine,
more focused on oncology and cancer treatment therapies. They claim that the main problem
with treating cancers is that there are many genetic variations that contribute to how cancer
affects certain people and as a result, whatever treatment is localized might have varying
affects on differing bodies. As a result, precision oncology, “…attempts to understand more
about how variations in our genes, proteins and other factors influence our health. The area of
precision medicine that addresses treatments for various cancers is called precision oncology”.
https://www.fda.gov/media/138005/download
9. If you were designing a new indirect instrument, how would you test your instrument?
Answer: For an indirect instrument I would test the instrument by making indirect
measurements, as direct measurements would most likely be hard to obtain. I would most
likely use mathematical formulas to take into consideration certain aspects of the scenario and
find results by solving for them theoretically.
10. You have the following results from a new test you have developed and the results have been
classified as follows:
The number of true positives = 78
The number of true negatives = 85
The number of false positives = 15
The number of false negatives = 12
What is your sensitivity and specificity?
Answer: My sensitivity is 0.867 and my specificity is 0.85.