Clinical Lab Data Flashcards
define accuracy
agreement between measured quantity and true value
define precision
agreement between repetitive measures
_________ is a test of reproducibility
precision
3 measures of precision
arithmetic mean
standard deviation
coefficient of variation
explain what coefficient of variation is
expresses standard deviation as a percentage of the mean
standard deviation/sample mean
measure of PRECISION
What confidence intervals are used to determine whether 2 tests can be used, solely based on how precise they are?
95% confidence intervals, plus minus 2 standard deviations
what are the 2 most important factors for reference intervals
gender and age
can a healthy person have an abnormal lab test value?
yes, bc reference intervals are designed to include 95% of the values from a healthy reference population, there is a 5% chance
true or false
abnormal results are a consequence of multiple testing
true
sensitivity refers to…..
the% of positive test results in patients with a particular disease
a sensitivity of 95% means…….
95% of patients with the disease will be affected by the test
5% with the disease will have false negative results
what is specificity?
refers to the % of negative test results in patients WITHOUT a particular disease
a specificity of 95% means….
95% of patients WITHOUT the disease will have a negative result
5% of patients WITHOUT the disease will have a false positive result
prevalence is defined as….
the % of the general population who have the disease
expressed as # of people with the disease per 100,000 people
what is a screening test
a test used to screen a population of people for the presence of a particular disease
screening tests that are performed on unselected populations in which disease prevalence is very low will yield……
overwhelmingly false positives even if the test has a very high specificity
CBC vs CBC with differential
CBC with differential includes types of WBC
in a CBC with differential, presence of _____ is an indicator of immune system status
lymphocytes
in a CBC with differential, _____ is an indicator of the ability to manage infection
granulocytes (neutrophils, bands)
the normal ratio of CD4:CD8 is….
2
what measures ALL phases of coagulation?
bleeding time
what measures the extrinsic clotting pathway?
prothrombin time (PT)
what measures the intrinsic clotting pathway?
partial thromboplastin time (PTT)
_______ is increased by administration of coumadin
prothrombin time (PT)
________ is increased by administration of heparin
partial thromboplastin time (PTT)
when would chloride levels be elevated
in dehydration