Intro to lab medicine Flashcards
What is screening used for?
to identify risk factors for disease and to detect disease in asymptomatic patients
What does screening accomplish?
early intervention, reduce disease morbidity and mortality
What are the characteristics of population for optimal screening?
high prevalence of disease, pt likely to be compliant with tests and treatment
What are the characteristics of disease for optimal screening?
significant morbidity/mortality, effective treatment available, presymptomatic period detectable, improved outcome from early treatment
What are the characteristics for optimal screening tests?
sensitivity, specificity, low cost and risk, confirmatory test available
How does screening benefit patient management?
evaluate severity, estimate prognosis, monitor disease, detect disease recurrence, select drugs/therapy
How does cost affect screening?
cost of test must be considered, associated risks, potential for additional testing, will results of test change management
Define qualitative
either positive or negative; the substance you are testing for is either present or absent
What are some examples of qualitative tests?
pregnancy tests, drug screens
Define quantitative
measured amt reported in mass or volume
Describe reference intervals and what they do
establish the normal range, are dependent on the lab and popn, determined by sampling a healthy popn. 95% of the results determine the normal range
What are some physiologic factors which may influence test results?
meds, altitude, occupation, age, gender, excercise, diet, pregnancy, diurnal variations, tobacco
Define accuracy
determined by its correspondence with the true value. is maximized by the calibration of lab equipment/quality control measures.
Define precision
measure of a test’s reproducibility when repeated on the same sample
Define sensitivity
ability of a test to detect the presence of disease. expressed as the % of patients w/disease who test positive
What does a test with 90% sensitity mean?
gives positive results in 90% of diseased patients and negative results in 10% of disease patients (false negatives).
What is a true positive result?
abnormal test results occurring in individuals who have the disease
What is a false negative result?
normal test result occurring in individuals who have the disease
Define specificity
ability to detect absence of disease and is expressed as the % of patients without disease in whom the test is negative
What does a test with 90% specificity mean?
gives negative results (true negatives) in 90% of patients without disease and positive results (false positives) in 10% of patients without the disease
What is a true negative result?
normal test results in a disease-free healthy individual
What is a false positive result?
abnormal test results in a disease-free healthy individual
What is an example of a highly specific test?
to check for gout would be an evaluation of the jt fluid for the presence of urate crystals
What is pretest probability?
the likelihood the patient has the abnormality that you are testing for based on risk factors, symptoms, h/o, physical exam
