Biomedical Engineering Reference
In-Depth Information
CHAPTER 9
Evaluation (Validation and Verification)
9.1 Introduction
We now arrive at the pinnacle of our design activity. Everything we have done, so far, has
led to this day…the day we see if our design works. The recent changes to medical device
legislation in Europe and tightening of existing guidelines elsewhere has made evaluation
(of medical devices before they are authorized for sale/use) ever more important. In the past
medical device designers were almost derisory in their attention to this aspect of the design
process. They left this part to someone else as if it were not their problem - well it is! It is
now impossible for you to ignore this important aspect of the design cycle; it is so important
that it has its own section in the PDS called Acceptance Criteria.
In the EC, this aspect is known as clinical evaluation ; under FDA guidelines it is called
validation and verification. . Verification means to compare design input to output; validation
means ensuring the device meets clinical requirements, is safe to use, and does what it is
supposed to (in a clinical sense). As I said in Chapter 4, I will call the whole evaluation .
There are two common forms of evaluation: in vitro and in vivo . The former means in a
laboratory, the latter means on living subjects. So, for example, a test that shakes a device to
pieces would be in vitro. A literature review selecting and confirming precedence would also
be in vitro. A test that counts how many times a patient uses a device per day would be
in vivo. We shall see how these two exhibit themselves in real life.
9.1.1 Clinical Trial or Clinical Evaluation: What Is the Difference?
There is a very important distinction to be made between these two. Firstly, which is higher
up the food chain? It is simple: a clinical trial is always a part of an overall clinical evaluation.
You cannot release a product without conducting a clinical evaluation, but you may have no
need to conduct a clinical trial. It is important to note that most countries now state that for
some devices clinical trials are a mandatory. For example, in the EC any Class III device must
have a clinical trial as a part of its evaluation. You must check for yourself what the current
regulations are in the states in which you wish to sell.
Clinical evaluation takes place prior to any release; this inherently means that anything
undergoing a clinical trial is a nonapproved product. In EC terminology it has no CE mark;
in the USA it has no 510(k). Hence a clinical trial, by definition, is conducted using a
 
 
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