Zusammenfassung der Ressource
Potential problems
physiological/clinical
data collection
- physiological variation
- For example if your GP took your blood pressure
three times in a short period of time,
- first reading is on average higher than the subsequent readings
- Take this into account taking the
measurements more than once and at different
times so that an average reading is calculated
and recorded.
- variation in the measuring instrument
- e.g. the blood test procedure or taking blood pressure
- BP variation =app of cuff before inflation and this can
change the final reading.
- so must be calibrated before, during and after
each study and data may need to be adjusted on
the basis of subsequent calibration.
- observer variation
- People taking blood pressure measurement may vary
in their ability to hear the sounds (if using the manual
device),
- might read the measurement incorrectly,
- might write down the incorrect result onto the data collection form.
- even experienced clinicians can vary in their ability to read an X-ray
- counteract this
- 2 exp ppl
- read X-rays
- other test results
- before study standardised criteria and
interpretation
- should be developed and included in the study protocol
- Experienced observers should practice with
more experienced observers
- all observers should be tested and corrected until
reliability is obtained both between observers and
within all observations taken by a single observer
- bias from interactions
- involving the person being measured, the measuring
instrument, and the observer.
- participant may learn over time how to use an instrument
better and so it might appear that the test results are
improving
- can happen with respiratory testing for asthma
- Interactions can occur between the
observer conducting the test and the
participant that introduces bias.
- For example a person's pulse rate decreases as
they become less anxious, or blood pressure can
increase when the reading is taken by a person of
the opposite gender
- even tho clinical tests used in health have
already been rigorously tested for reliability
and validity.
- Variation still occurs
- Records= measurement of interest
- may not have been conducted or recorded
- the information may have been
recorded by many different people in an
incomplete and non-standardised way
- Limited value
- establish if a participant has had the
disease of interest, particularly in
case-control and cohort studie
- exposure and confounding variables are not usually obtained