interpreting test result Flashcards
what is the basic clinical process?
it is a consultation that is a history or exam and then a lab request and then a report
what is the purpose of the tests?
to rule in or rule out - most will rule out and form a differential diagnosis
how many diagnoses depend on laboratory tests?
up to 70%
what is the service discipline of chemical pathology?
diagnosis, screening, monitoring and therapeutic control
who does the service discipline provide advice to?
individual cases and clinical care protocols
what is the role of the major clinical science in chemical pathology?
it is research into the biochemical basis of disease, it provides support for clinical trials, science for diagnosis and bridges pre-clinical and clinical subjects
what are the major subjects of chemical pathology?
metabolism, endocrinology, homeostasis and physiological systems
what is the normal range?
it is the range of results that can be expected in a healthy population - it defines the values of biochemical tests found in a healthy population against which the patient values can be compared
what is the issue with the normal range?
it is not really normal - all patients differ and we do not use ‘normal’ patients all the time when defining - artificial concept - no clear boundaries exist
what is the reference range?
it is the frame of reference to make a decision against - you take a normal distribution of patients and put +/- 2SDs to find the range - they are a guide - not fixed
what are the difficulties of ideal tests?
they are rarely available - sensitivity and specificity rarely coexist - there is always overlap
how would you improve tests?
chose a more appropriate sample normal population,. use a combination of tests with low cost sensitive test first line and high cost specific test second line and combine tests to test for multiple things at once - e.g. PKU and hypothyroidism in neonatals
what are appropriate normal populations?
same presenting symptom, same age, gender, hospitalised normals and same underlying condition
explain the factors affecting reference ranges?
age gender diet - change status ethnicity time of month and day - hormones time of year - vit D and calcium weight stimulus glucose tolerance
what are the factors that affect interpretation?
different therapeutic ranges for different drugs in different patients and action limits - may not be a normal range or may be more interested in risk factors
what is the lower and upper ranges for therapeutic control?
lower - effectiveness
upper - toxicity
what is the therapeutic range for cholesterol?
we want people on the lower part of the curve - ideal is 5.2, range is from around 6.5-12 - when lower than this want to focus on diet and in this want to focus on medications
what is the therapeutic control for phenytoin?
want to be at a level where are neither under treated nor over but are fit free. Titrate the dose and monitor levels of drugs to see: effectiveness, if they are taking and toxicity.
how would you treat a patient with paracetamol poisoning?
take dose and read to see if need antidote. Find out how much taken and replace glutathione to divert toxic products into harmless - prevent liver failure - methionine if given soon enough can reverse - by 12 hours
what must you ensure when interpreting biochemical values?
they are read in light of appropriate reference range, they are taken at right conditions and you understand normal physiological regulation for each patient `
what is protein glycosylation?
protein + glucose = advanced glycosylated endproducts
non-enzymatic process
rate dependent on time and glucose concentration
what it HbA1c?
it is a stable glycosylated haemoglobin - percentage concentration indicates cumulative glucose exposure
what is aspirin often used for?
over dose - salicylate OD
what can paracetamol OD result in?
acidosis
