Lecture 4: Evidence Evaluation: How do we identify disease in populations? Flashcards
What is a test?
Lab test, x-ray, ultrasounds, the answer to a patient question, the identification of a symptom
What is the difference between screening and diagnosis?
- If there are no symptoms: screening
- If there are symptoms: Diagnosis
What is screening?
Identify the possible presence of an as-yet-undiagnosed disease in a person without signs or symptoms
What is a diagnosis?
Determining which disease or condition explains a person’s signs or symptoms
Commonly used measures for evaluating the
clinical performance of diagnostic and screening tests: Sensitivity
the probability that an individual with the disease has a positive test result
Commonly used measures for evaluating the
clinical performance of diagnostic and screening tests: Specificity
he probability that an individual without the disease has a negative test result
Commonly used measures for evaluating the
clinical performance of diagnostic and screening tests: Positive predictive value
the probability that an individual with a positive test result has the disease
Commonly used measures for evaluating the
clinical performance of diagnostic and screening tests: Negative Predictive Value
the probability that an individual with a negative test result does not have
the disease
Commonly used measures for evaluating the
clinical performance of diagnostic and screening tests: Positive Likelihood Ratio
he probability that an individual with the disease has a positive test result,
divided by the probability that an individual without the disease has a positive test result (that is,
sensitivity/(1−specificity))
Commonly used measures for evaluating the
clinical performance of diagnostic and screening tests: Negative likelihood ratio
the probability that an individual with the disease has a negative test result, divided by the probability that an individual without the disease has a negative test result (that is,(1−sensitivity)/specificity)
Commonly used measures for evaluating the
clinical performance of diagnostic and screening tests: Area under the receiver operationg characteristic curve (AUROC)
he probability that a classifier will
correctly rank a randomly chosen person with the disease higher than a randomly chosen person
without the disease (that is, the area under a plot of sensitivity against (1−specificity))
Sensitivity ranges from?
0% to 100%
Specificity ranges from
0 - 100%
Does specificity take prevalence into account?
No
What is prevalence?
the proportion of individuals in a population having a disease at a
particular time point
