Epidemiology Flashcards
5 D’s (primary health outcomes)
Death
Disease
Dissatisfaction
Disability
Discomfort
Prevalence
of people with disease / entire pop.
Cumulative Incidence
CI = (# new cases of disease in amt of time)/population at risk
Incidence Rate
RI = (# new cases of disease in amt of time)/person-years
What is sensitivity?
True positive rate.
Number of people who have the disease and test positive.
TPR = TP /(TP + FN)
What is specificity?
True negative rate.
Number of people who don’t have the disease and who test negative.
TNR = TN / (FP + TN)
What is PPV?
Positive predictive value.
Number of people who test + and who have the disease.
PPV = TP /(TP + FP)
Increases with prevalence.
What is NPV?
Negative predictive value.
Number of people who test - and who do not have the disease.
NPV = TN /(TN + FN)
Decreases with prevalence.
LR+?
Likelihood of disease given a positive test.
LR+ = sensitivity / (1-specificity)
LR+ = True positive rate /False positive rate
LR-?
Likelihood of disease given a negative test.
LR- = 1-sensitivity / specificity
LR- = False negative rate /True negative rate
What does a low amount of false negatives mean in terms of sensitivity and specificity?
High sensitivity!
Sensitivity = TP /FN
What does a low specificity mean in terms of number of positive results?
Low specificity = lots of false positives
3 types of data
Nominal: no inherent order (sex, ABO, genetic markers)
Ordinal: some inherent order: pain, QoL
Interval: continuous or discrete data. inherent order.
4 characteristics of our measurements
- Valid
- Reliable
- Responsive
- Interpretable
Median = ___th percentile?
50%.
50% of values fall below the median.
