CHAPTER 9: Principles of Serological Testing

Question 1

If serum is not tested immediately, how should it be treated?
a. It can be left at room temperature for 24 hours.
b. It can be stored in the refrigerator for up to 72 hours.
c. It can be stored in the refrigerator for up to 48 hours.
d. It needs to be frozen immediately.

Answer 1

b. It can be stored in the refrigerator for up to 72 hours.

Question 2

A 1:750 dilution of serum is needed to perform a serological test. Which of the following series of dilutions would be correct to use in this situation?
a. 1:5, 1:15, 1:10
b. 1:5, 1:10, 1:5
c. 1:15, 1:10, 1:3
d. 1:15, 1:3, 1:5

Answer 2

a. 1:5, 1:15, 1:10

Question 3

How much diluent needs to be added to 0.2 mL of serum to make a 1:20 dilution?
a. 19.8 mL
b. 4.0 mL
c. 3.8 mL
d. 10.0 mL

Answer 3

c. 3.8 mL

Question 4

If glacial acetic acid needs to be diluted with water to make a 10% solution, what does the glacial acetic acid represent?
a. Solute
b. Diluent
c. Titer
d. Serial dilution

Answer 4

a. Solute

Question 5

A pipette that has markings all the way down to its tip is called a
a. volumetric pipette.
b. serial pipette.
c. graduated pipette.
d. micropipette.

Answer 5

c. graduated pipette.

Question 6

A serological test requires 5 mL of a 1:50 dilution. How much serum is required to make this
dilution?
a. 0.5 mL
b. 0.01 mL
c. 1.0 mL
d. 0.1 mL

Answer 6

d. 0.1 mL

Question 7

If 0.02 mL of serum is diluted with 0.08 mL of diluent, what dilution of serum does this represent?
a. 1:4
b. 1:5
c. 1:10
d. 1:20

Answer 7

b. 1:5

Question 8

A tube containing a 1:40 dilution is accidently dropped. A 1:2 dilution of the specimen is still available. A volume of 4 mL is needed to run the test. How much of the 1:2 dilution is needed to remake 4 mL of a 1:40 dilution?
a. 0.2 mL
b. 0.4 mL
c. 0.5 mL
d. 1.0 mL

Answer 8

a. 0.2 mL

Question 9

If 0.4 mL of serum is mixed with 15.6 mL of diluent, what dilution of serum does this represent?
a. 1:4
b. 1:40
c. 2:70
d. 1:80

Answer 9

b. 1:40

Question 10

How much diluent needs to be added to 0.1 mL of serum to make a 1:15 dilution?
a. 1.4 mL
b. 1.5 mL
c. 5.0 mL
d. 15 mL

Answer 10

a. 1.4 mL

Question 11

Which of the following choices would be considered a serial dilution?
a. 1:5, 1:15, 1:20
b. 1:2, 1:10, 1:25
c. 1:15, 1:30, 1:40
d. 1:5, 1:15, 1:45

Answer 11

d. 1:5, 1:15, 1:45

Question 12

The following dilutions were set up to titer an antibody. The following results were obtained: 1:4 +, 1:8 +, 1:16 +, 1:32 +, 1:64 -. How should the titer be reported out?
a. 4
b. 16
c. 32
d. 64

Answer 12

c. 32

Question 13

If a serological test is positive for an individual who does not have a particular disease, the result was caused by a problem with
a. sensitivity.
b. specificity.
c. accuracy.
d. poor pipetting.

Answer 13

b. specificity.

Question 14

Which of the following would be the correct way to make a 5% solution of hydrochloric acid from concentrated hydrochloric acid?
a. 0.5 mL of acid and 9.5 mL of water
b. 0.5 mL of acid and 95 mL of water
c. 0.1 mL of acid and 9.9 mL of water
d. 0.1 mL of acid and 4.9 mL of water

Answer 14

a. 0.5 mL of acid and 9.5 mL of water

Question 15

What is the final dilution of serum obtained from the following serial dilutions: 1:4, 1:4, 1:4, 1:4, 1:4, 1:4?
a. 1:24
b. 1:256
c. 1:1,024
d. 1:4,096

Answer 15

d. 1:4,096

Question 16

A new laboratory assay gave the following results: number of patients tested = 100; number of true positives = 54, number of true negatives = 42; number of false positives = 2; number of false negatives = 2. What is the specificity of this assay in whole numbers?
a. 75%
b. 85%
c. 95%
d. 98%

Answer 16

c. 95%

Question 17

What is the sensitivity of the assay in Question 16?
a. 84%
b. 90%
c. 92%
d. 96%

Answer 17

d. 96%

Question 18

A screening test gave the following results: number of patients tested = 150; number of true positives = 50; number of true negatives = 85; number of false positives = 5; number of false negatives = 10. What is the positive predictive value rounded off to a whole number for a patient whose test is positive?
a. 91%
b. 83%
c. 89%
d. 56%

Answer 18

a. 91%