Scientific Concept of the National Cohort (status ... - Nationale Kohorte

A.5 Methods for quality assurance and quality control
by the competence center on imaging and implemented and trained during the centralized
technologist training courses. If insufficient image quality is detected, additional MRI sequences
will be acquired to maintain a complete protocol. If there is any technical failure,
the technical service of the vendor will be notified and a re-examination will be offered to
the subjects.
Second-line quality check: A second-line quality check will be performed at the centralized
reading core at the competence center on imaging prior to the first-line reading. This
check will include similar items as for the first-line quality check but will additionally involve
subjective assessment by a radiologist. If impaired image quality is detected, the respective
imaging center will be contacted and any causes will be investigated. If a higher frequency
of cases with impaired image quality is detected at one imaging site, retraining and site
visits will be employed.
MRI reader certification: All imaging examiners will undergo training in the respective clinical
departments before they enter the study. The potential examiner will first be certified
after he/she has been trained for at least 3 months. During this period, each trainee is required
to examine at least 2 x 25 images for continuously distributed findings and at least 2
x 100 findings for dichotomous variables. Intra- and interobserver variabilities for selected
major characteristics are determined. Statistical analyses are conducted using Bland and
Altman plots for continuously distributed variables. The mean bias will not exceed 5%, and
2 SD of the bias will not exceed 25%. Statistical analyses for dichotomized variables are
performed by κ statistics, whereby κ > 0.8 is expected. Trainees who do not fulfill the quality
criteria after 3 months of training are subjected to further mandatory training. The additional
training includes an individualized calibration of the trainee based on the results of his/her
first certification. Should there be no improvement, the trainee is replaced by another person.
A web-based certification procedure is planned.
Further efforts focus on the external validity of the data. Imaging modalities will be intensively
discussed with national and international experts in advance of the field phase of
the National Cohort. To support comparability of the National Cohort with other populationbased
studies, we will invite external observers to take part in the web-based certification
procedures on a regular basis.
A.5.8 quality assurance and quality control during follow-up
In parallel to the processes described above, the study centers will be busy with continuously
maintaining contact to the other members of the cohort, deriving information from these
sites, from their own doctors, and from institutions and other data sources as described in
Sect. A.3.8. In addition to the quality management aspects presented in that section, the
more general task will be to implement a system that makes it possible to compare the results
of the different center-specific monitoring processes at the central level. A set of quality
indicators, e.g., percentage of participants who are successfully tracked, percentage of
responders giving information on contacts to the health system, completeness of vital status
or death certificate information, will be created and compared across centers. By using this
benchmark process we can identify possible problems, but also chances for improvement.
Concerning endpoint information, a step-wise validation procedure is envisaged:
1. For cancer, stroke, and CHD all events of category (a) and a random sample of category
(b), as described in Sect. A.3.7.5 will be seen by a central endpoint committee.
2. For all other endpoints, a random sample of the documented events will be assessed
by dedicated expert panels.
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A.5