Reference Range
Range of values within a population of people who do not have a given disease. Upper and Lower limits
Desirable Range
Prognosis related ranges
Ex: A1C
Therapeutic range
Measure effectiveness of medication
Screens for possible toxicity due to medication
Sensitivity
Focuses on population of individuals who HAVE the disease
Capacity to identify individuals with the disease
Sensitive test
LOW diagnostic threshold (higher false positives)
Examples of sensitive tests
Newborn screening
Glucose test for gestational diabetes
Specificity
focuses on a population of individuals withOUT the disease
Specific test
high diagnostic threshold (higher false negatives)
Positive predictive value
- focuses on people with a positive test result
- the likelihood that a positive test result identified someone with the disease
Negative Predictive value
- focuses on people with a negative test result
- the likelihood that a Negative test result identifies someone withOUT the disease
Example of Positive predictive value
TB test in a community with lots of TB cases (prison)
Example of Negative predictive value
D-dimer for pulmonary embolism
Prevlence
- # of existing cases in a population
- usually in %
48% of Americans have hypertension
Incidence
- number of NEW cases occurring within a period of time
- usually in one year
- sore throat
Reasons for ordering laboratory test (4)
- Diagnosis of disease
- Monitoring diseases
- screening for disease
- Research
Questions to ask before ordering test (5)
- Why is it needed
- What are the consequences
3, How good is the test in discriminating between healthy and disease - How will results be interpreted
- influence patient management and outcome?
Laboratory Testing Cycle
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