Page 204 - Safety Risk Management for Medical Devices

CHAPTER 22

Verification of Risk Controls

Abstract
Risk Controls must be verified for both implementation and effectiveness. Objective evidence is
required to establish and support claims of verification.
Keywords: Risk Controls; verification; testing; implementation; effectiveness

Risk Controls must be verified for both implementation and effectiveness. Objective
evidence is required to establish and support claims of verification.
The primary means of verification is testing. But sometimes visual inspections are
used to verify the implementation of a Risk Control. For example, if the Risk
Control is the installation of a red light, visual inspection for the presence of the red
light is the easiest way to verify implementation. Caution should be exercised with
respect to reliance on visual inspections, particularly if the visual inspection is done by
one tester over a long period of time. It has been shown that after 2 /2 hours of
1
continuous visual inspection, the propensity for error increases significantly. Also,
visual inspection is subjective.
Be alert to optical illusions. There are many examples of optical illusions such as
the images below. In the left image, (A) appears to be smaller than (B), while they are
the same length. In the right image the horizontal lines appear to not be parallel,
when in fact they are parallel.

When doing testing, clear objectives and expectations are important. Human
beings need to know what is important and needs their attention. Often people are
given ambiguous objectives and expected to focus on many things. In such circum-
stances, it is easy for a tester to miss the things that they should notice.

Safety Risk Management for Medical Devices r 2018 Elsevier Ltd.
DOI: https://doi.org/10.1016/B978-0-12-813098-8.00022-2 All rights reserved. 183