2.3 Acceptable Quantity of Clinical
Data
2.3.1 Sample Size
The choice of the sample size is one of the primary
endpoints the sponsor has to determine for the clinical
study.
As we can’t include all the population of interest,
we should determine what is the minimum number of
patients that would reflect as much as possible the
total population of interest, and therefore make study
results statistically significant.
The MDR requires to document the choice of
sample size, and to provide a rationale explication of
the procedures and the methods used.
The sponsor should define what endpoints would
be statistically measured through the clinical study to
demonstrate the device general safety and
performance conformity assessment. To assess
quality and performance of an implantable medical
device the survival rate is usually measured.
2.3.2 Duration of Clinical Study
The duration of a clinical investigation is also crucial
and must be considered while planning the PMCF.
“The follow-up period during the clinical investigation
shall permit the demonstration of clinical performance,
effectiveness or safety over a period of time sufficient to
represent a realistic test of the investigational device and
allow any risks associated with adverse device effects to be
identified and assessed” (ISO 14155 : 2020).
“Although there is not enough information yet available
to calculate exactly how long a hip replacement will last,
using available arthroplasty registry data, we estimate that
about three-quarters of hip replacements last 15–20 years
and just over half of hip replacements last 25 years in
patients with osteoarthritis” (How long does a hip
replacement last? A systematic review and meta-analysis of
case series and national registry reports with more than 15
years of follow-up - Jonathan T Evans, Jonathan P Evans,
Robert W Walker, Ashley W Blom, Michael R
Whitehouse*, Adrian Sayers* - 2019).
Taking into consideration the average duration of
the hip joint life cycle and the common practice in
designing the hip replacement PMCF studies, we
estimated the minimum duration of the study at 10
years.
2.4 Acceptable Quality of Clinical Data
“Clinical investigation that are currently being conducted
with respect to Directive 93/42/EC and Directive
90/385/EC by the date of application of the MDR, can
continue to be conducted” (MDCG 2021-6).
Therefore, the Clinical investigation protocols
that have been approved under Directive 90/385/EC
can be keep going, as long as the quantity and quality
of the data are sufficient. But what constitutes the
quality of the data?
The quality appraisal of the clinical data is
uncertain, as it has to take into consideration several
aspects.
MEDDEV 2.7/1 rev. 4. point 9. suggests to
evaluate two main sources: the methodological
quality of the data, and the relevance of the data.
2.4.1 Methodological Quality
Different methods are available to conduct a clinical
study.
In case of legacy device observational prospective
or retrospective studies are most commonly used.
We are encouraged to conduct the methodology
evaluation to assess whether there are any points that
can be improved.
We have grouped the information from Appendix
A6 General principles of clinical evaluation of
MEDDEV 2.7/1 rev. 4. to constitute the checklist of
the desired parameters for a high-level scientific
validity study to demonstrate adequate clinical
performance and clinical safety.
Below are the points that should be taken into
consideration while assessing the methodological
quality of the study:
- Sufficient information on elementary aspects
- Proper statistical methods
- Adequate controls
- Proper collection of mortality and serious
adverse events data
- Legal activities
- Schedule for PMCF activities
Let’s see in details those points.
- Sufficient Information on Elementary Aspects
The clinical data should necessarily contain the
following elementary aspects:
a) Methods used
b) Products used
c) Number of patients
d) Clinical outcomes
e) Undesirable side-effects
f) Confidence intervals/ calculation of statistical
significance
g) Reference to the harmonised standards or
guidances.