Verification of preoperative screening for bleeding tendency in patients that report bleeding symptoms

Each year 15,000 patients are screened before surgery at the outpatient
department of anesthesiology on bleeding tendency. A short bleeding
questionnaire is being used to guide the anesthesiologist if a patient has a
possible bleeding tendency or not: a negative questionnaire can safely be
regarded as a true negative, but in the case of a positive questionnaire little
guidance is at hand what to do next. Lengthy laboratory tests, which only test
part of the coagulation cascade, are done, but give to little information on
bleeding tendency.
New point-of-care devices and genetic tests are faster and give a more overview
of the coagulation cascade. Using these tests in a screening scenario has not
been researched yet.
A more elaborate questionnaire for bleeding tendency, in which a score can be
computed, could possibly narrow down the false positives while maintaining the
sensitivity from the short bleeding questionnaire now being used.
A control group of 120 pre-operative patients is added to make reference values
for these tests and questionnaire in this specific group, in order to judge
test results from our patients as 'normal' or 'abnormal'.

The main object is to evaluate the validity of a diagnostic screening package
for bleeding tendency consisting of point-of-care devices when compared with
the gold standard for bleeding tendency diagnosis.

Other objects which will be investigated are:
- the development of a more efficient screening algorithm by use of a bleeding
risk score in patients who have one or more positive answers in the current
short questionnaire,
- describing the differences in the usages of both human and synthetic blood
products between the patient groups from this study,
- the validity of alternative/experimental methods such as a genetic test
package for diagnosis of bleeding tendency in patients with possible disorders
of hemostasis.
- Determine reference values for the tests/questionnaire in the screenings
algorithm for this pre-operative group.

This is a diagnostic study to estimate sensitivity, specificity, positive and
negative predictive value of a new package of diagnostic tools consisting of
point-of-care devices, ATP secretion analysis and DNA-analysis (study package)
when compared with the gold standard package. For this blood (57ml) needs to be
withdrawn from an antecubital vene and a more elaborate bleeding questionnaire
needs to be reviewed with the help of research personnel. This will be done in
study patients and control group patients.

Burden and risk associated with participation
Subjects have to make a appointment of fastened blood withdrawal. The total
research time is 30 minutes for one subject.
They are subjected to little risk. Blood withdrawal of 57ml will not endanger
subjects.

Benefit
Subjects will receive a card with detailed results and the interpretation of
the results. This card can be used as a future reference card elsewhere.

Possible disadvantage
Subjects that choose for feedback on the genetic testing can encounter
consequences for future insurances and mortgages, if a gene mutation is found.
Patients are well informed about these consequences, so they can make an
informed choice about feedback on DNA testing.

Group relatedness
Group selection is based on the population of patients attending the outpatient
department of anesthesiology. No other base population can be used for this
study. This is also true for the control group, as new reference values need to
be determined for each specific patient group.