Classifying Medical Devices - Medical Device Design: Innovation from Concept to Market - page 12

Table 2.1: Classifications in the USA and Europe

Risk Low Risk High Risk

In Europe the classifications are:
EU I IIa IIb III

In the USA the classifications are:
USA I II III

Within the EU they are stipulated within 93/42/EC Annex IX ( EC, 1993 ). Both documents
are freely available on the World Wide Web, as are those for any other country. As a medical
device designer you must have an up-to-date copy of the classification rules to hand at all
times. There is a fundamental difference between the two systems. In the USA classification
is by precedent and is undertaken by the FDA; that is, you have a classification by comparison
with decisions already made by a panel. In Europe there is a long list of questions to answer
and you decide on your classification. However, if you try and cheat the system by “under-
classifying” you will fail.

The classifications are based on risk to the patient (as illustrated by Table 2.1 ). As we will
see later, risk is a very important aspect of design control; understanding risk to the patient
(and to the clinical team/operator) is fundamental. The FDA process is not a good vehicle to
help us understand patient risk and classification. We will use the EU model to understand
how classifications are made. For this exercise you will need a copy of 93/42/EC Annex IX
at hand.

Table 2.2 illustrates how the EC medical devices rules define the classification of a device.
The symbols indicate that this particular rule defines this particular class of device.
Hence, if you think your device is likely to be Class III it will fall into the definitions
described by one of Rules 6, 7, 8, 13, 14 and 17. Do not assume that these are the
only rules you need to consider; all rules need to be examined to make sure that our
classification is correct.

Before we go further we need to understand some definitions:

Invasive device: a device that penetrates inside the body either through an orifice or
through the surface of the body.

Surgically invasive device: any device that enters the body other than through an
established body orifice.

Transient duration: continuous use of less than 60 minutes.

Short-term duration: continuous use of not more than 30 days.

Long-term duration: continuous use of greater than 30 days. ( EC, 1993 )