Week 6: Lab Test Interpretation

Question 1

What is the “reference range” RR?

Answer 1

Within 2 standard deviations (SD) = normal range, or reference range. If it is outside, it is abnormal.

Question 2

What is the definition of analytical variation?

Answer 2

Test result reproducibility. Ex. how much does the test measurement vary between replicate tests?

Question 3

What is biological variation?

Answer 3

Usually within RR. How much does a test vary between 2 samples taken at different times from 1 person?

Question 4

What is a sensitivity test? What is the equation for it? What does a 100% sensitive test mean?

Answer 4

Sensitive test = one that detects all of the people with a disease.
Sensitivity = (TP)/(TP + FN). 100% sensitive means no false negatives.

Question 5

What is a specificity test? What is the equation, and what does 100% specific indiciate?

Answer 5

A test that detects all of the people without a disease.
Specificity = TN/(TN + FP)
100% specific test has no false positives.

Question 6

Setting the diagnostic cutoff at the ______ ______ provides the optimal balance of ______ and _______ for a test, compared to any other location for the cutoff. It will have a small number of what?

Answer 6

Critical value, specificity, sensitivity, false neg/pos

Question 7

What is the equation of the positive predictive value of a test? What does it mean?

Answer 7

PPV = TP/(TP + FP)
It means the likelihood that the test, if reported positive, means the disease is present.