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

A.3
A.3 Study design
In addition, as many subjects are not able to give details about newly diagnosed diseases
(e.g., invasive breast cancer versus in situ breast cancer; angina pectoris versus MI; stenting
without prior MI versus stenting because of acute MI, etc.), the questionnaires will query
diagnosis and treatment circumstances that can indicate incident outcomes of interest as
closely as possible. For example, data from subjects who were admitted to hospitals for a
cardiologic diagnostic check-up or treatment or for a cancer check-up will be validated by
hospital chart review, etc.
In a second step, selected self-reported incident diseases (and dates of diagnosis) will be
systematically verified by contacting the participant’s pertinent physician(s) who made
the diagnosis (i.e., general practitioners, specialists, or hospitals/clinics, respectively). Only
verified cases will finally be considered for analyses, so as to ensure high specificity.
For certain diseases, we will also obtain more specific medical information from the physician
or use organized access to patients’ clinical records and/or pathology records for direct
information retrieval, e.g., for further classification into specific subtypes of disease. For example,
information from patients’ clinical records will be used to classify cases of stroke into
specific subtypes (ischemic versus hemorrhagic). Likewise, information from clinical records
and pathology records will be used for the specific coding of histologic subtypes of cancer.
In addition to active follow-up, we will make use of linkage with external data sources for
detecting and verifying incident diseases. This is particularly relevant in the field of cancer,
where epidemiologic cancer registries (with varying degrees of completeness of coverage)
have now been established in every state in Germany. These registries will also be
used to ascertain incident disease. Supporting epidemiologic research in the field of cancer
etiology is among the primary aims of cancer registries in Germany. For many cases of
cancer and for many cancer types, the use of cancer registry data will reduce the workload
for further active verification of clinical and/or retrieval of pathology records, and thus will
both facilitate the follow-up process and allow for major cost savings.Several successful
examples exist in Germany to support the aforementioned strategy to ascertain incident disease.
Similar strategies have been used in the Heinz Nixdorf Recall Study, CARLA, SHIP,
EPIC, and KORA studies 746, 747 .
Information on vital status will be collected from population registries at regular intervals for
the participants who have not taken part in the follow-up or reassessment procedures. For
subjects who have died, the death certificate that provides information on the cause of
death will be obtained from the public health offices. A National Mortality Registry is presently
being planned in Germany. As this national registry is expected to become progressively
operational and increase its coverage – which will probably be not the case before year 3
of the study – the procedure described above will be gradually substituted by data retrieval
from this registry following a validation phase with parallel ascertainment of approximately
another 2 years.
The use of secondary data from the health system as described in Sect. A.3.8 will be tested
for its usability to support the follow-up process. Individual linkage to secondary data has a
significant potential as an additional source of follow-up information 748 .
For assessment of prevalent diseases at baseline we plan to use similar strategies, in conjunction
with the results from physical and medical examinations conducted as part of the
baseline recruitment protocol.
For ascertainment of dementia, depression, headache, and RLS, scores based on questionnaires
will be established that can be used to supplement the self-reported data on
physician-diagnosed diseases. These scores are described in more detail in Sect. A.2.2
and A.2.3.
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