Lab test performance

Question 1

Definition: reference interval

Answer 1

a selected fraction, usually central range of a population (95%) of apparently healthy individuals of a frequency distribution

Question 2

specificity

Answer 2

percentage negativity of test results in patients who are free of disease
= TN/TN+ FP

Question 3

sensitivity

Answer 3

percentage positivity of test results in patients who have the disease = TP/TP+FN

Question 4

positive predictive value

Answer 4

the percent probability that a positive test result correctly predicts the presence of the disease TP/TP+FP

Question 5

negative predictive value

Answer 5

the percent probability that a negative test result correctly predicts the absence of disease TN/TN+FN

Question 6

predictive value of a test changes with….

Answer 6

the prevalence of the disease in the population

Question 7

Receiver operating characteristic (ROC) curve

Answer 7

a graphical means to assess a test’s performance. A plot of false positive rate (1-specificity) against the true positive rate (sensitivity)

Question 8

enzymes are mainly located in the…

Answer 8

cytosol, various organelles

Question 9

isoenzyme

Answer 9

different enzymes catalyzing the same reaction

Question 10

the activity of an enzyme in the blood represents…

Answer 10

a balance between its rate of liberation into extracellular space and its rate of clearance from extracellular space

Question 11

Cytosolic enzymes

Answer 11

The majority of enzymes used clinically, released earlier and to a greater extent than those from various organelles