Laboratory Medicine Flashcards
What are two topics related particularly to blood/fluid analysis?
Sensitivity and specificity, predictive value, and post-test probability
How close a test result is to the actual value
-Sometimes called validity
Accuracy
Reproducibility or reliability
Precision
The 95% confidence limits are given by the
Mean +/- 2 SD
Defined as how many people with the disease will have a positive test
Sensitivity
How can we calculate sensitivity?
Sensitivity = True positives / Those with disease
Defined as how many people without disease will have a negative test
-How well test can detect absence of disease
Specificity
How do we calculate specificity?
Specificity = True negatives / Those without disease
Defined as the chance that the result is actually correct
Predictive value
How do we calculate the:
- ) PV (+)
- ) PV (-)
- ) PV (+) = true positives/all positive tests
2. ) PV (-) = true negatives/all negative tests
The prevalence or likelihood of disease (pre-test probability) alters the
Predictive value
As the pre-test probability of disease increases, the predictive value of a positive result
Increases
For many diseases, we assume that pathology is the
Gold standard
When using pathology/cytology as a reference standard, Sensitivity is usually higher with a greater amount of
Tissue
Excisional biopsy or partial organ removal is more sensitive than
Cytology
