Deck 8: Serology Laboratory Math

Question 1

Children who flew in an trans-Atlantic airplane have been exposed to the new virulent strain of influenza. A laboratory has developed a 6-minute antigen assay from nasal swabs to diagnose the disease. The lab ran this test on 1000 samples. In a longer test that is considered the gold standard assay, 200 of these samples were found to be true positives and 800 true negatives. When tested by the new antigen assay, 150 of the true positives tested positive, and 790 of the true negative samples tested negative.
What is the efficiency of the assay?

A)94.00%
B)90.00%
C)96.75%
D)95.00%

Answer 1

94.00%

Question 2

If you make a 1:20 dilution and follow it with a 1:5 dilution, what dilution do you now have?

A)1:25
B)2:16
C)1:100
D)20:50

Answer 2

1:100

Question 3

What is the dilution in the fourth tube in a 10-fold serial dilution when the first tube is 1:10?

A)1:10000
B)1:1000
C)1:40
D)1:80

Answer 3

1:10000

Question 4

One hundred children with strep throat are tested by a new technique; 98 of them test positive and 2 of them test negative. One hundred children who do not have strep are also tested, and 5 of them test positive.

A)The sensitivity of the assay is 95%.
B)The sensitivity of the assay is 99%.
C)The sensitivity of the assay is 98%.
D)The specificity of the assay is 98%.

Question 5

A hospital has a high incidence of Group B neonatal sepsis, that is, 4 cases per 1000 live births. Applying the specificity above, what is the positive predictive value?
a.28.6%
b.348%
c.3.80%

Question 6

If you make a 1:10 dilution and follow it with a 1:5 dilution, what dilution do you now have?

A)1:50
B)2:16
C)1:15
D)2:50

Question 7

You have 0.5 ml of serum for your experiment. You need to make 1 ml of a 1:2 dilution. Do you have enough?

A)yes
B)no
C)yes, if there are high titer antibodies
D)yes, if there are low titer antibodies

Question 8

Children who flew in an trans-Atlantic airplane have been exposed to the new virulent strain of influenza. A laboratory has developed a 6-minute antigen assay from nasal swabs to diagnose the disease. The lab ran this test on 1000 samples. In a longer test that is considered the gold standard assay, 200 of these samples were found to be true positives and 800 true negatives. When tested by the new antigen assay, 150 of the true positives tested positive, and 790 of the true negative samples tested negative.
What is the specificity of this antigen assay?

A)75.00%
B)90.00%
C)98.75%
D)95.00%

Question 9

A hospital has a high incidence of this new strain of influenza, and that is 4 cases per 10000 live births. Applying the specificity found in question 17 what is the positive predictive value.

A)24.24%
B)3.10%
C)34.89%
D)50.00%

Question 10

The definition of titer is the

A)reciprocal of the first negative dilution
B)reciprocal of the last positive dilution
C)first negative dilution
D)last positive dilution

Question 11

If you have 5 ml of a 1:40 dilution and add 5 more ml, what dilution do you now have?

A)a 1:45
B)a 1:200
C)a 1:80
D)a 1:100

Question 12

If I make a 1:10 dilution, take 0.2 ml of it, and add 0.8 ml of buffer to it, what is the new dilution?

A)1:10
B)1:40
C)1:50
D)20:80
E)None of the above

Question 13

You have 0.4 ml of serum for your experiment. You need 1 ml of a 1:2 dilution. Do you have enough serum to make the required dilution?

A)no
B)yes
C)yes, if there are high titer antibodies
D)yes, if there are low titer antibodies

Question 14

If I have 0.2 ml of a 1:10 dilution and need a 1:40 dilution, how much buffer should I add?

A)0.8 ml
B)0.6 ml
C)1.0 ml
D)0.4 ml

Question 15

What is the dilution of the fourth tube in a 1:10 serial dilution if the first tube is a 1:3 dilution?

A)1:30
B)1:81
C)1:300
D)1:3000
E)1:27

Question 16

Children who flew in an trans-Atlantic airplane have been exposed to the new virulent strain of influenza. A laboratory has developed a 6-minute antigen assay from nasal swabs to diagnose the disease. The lab ran this test on 1000 samples. In a longer test that is considered the gold standard assay, 200 of these samples were found to be true positives and 800 true negatives. When tested by the new antigen assay, 150 of the true positives tested positive, and 790 of the true negative samples tested negative.
What is the sensitivity of this assay?

A)75.00%
B)90.00%
C)96.75%
D)95.00%

Question 17

If you have 5 ml of a 1:20 dilution and add 5 more ml, what dilution do you now have?

A)1:40
B)1:30
C)1:25
D)1:100

Question 18

Group B Strep that an infant is exposed to in the vaginal canal can cause neonatal fatalities in 48 hours, and the current test for diagnosis can take 24-48 hours. A laboratory has developed a 6-hour antigen assay to diagnose the disease. The lab ran this test on 2000 samples. Using the gold standard assay of culture, 500 of these samples were found to be true positives and 1500 true negatives. When tested by the new antigen assay, 450 of the true positives tested positive, and 1485 of the negative samples tested negative.
What is the sensitivity of this assay?

A)96.75%
B)90.00%
C)99.00%
D)95.00%

Question 19

Group B Strep that an infant is exposed to in the vaginal canal can cause neonatal fatalities in 48 hours, and the current test for diagnosis can take 24-48 hours. A laboratory has developed a 6-hour antigen assay to diagnose the disease. The lab ran this test on 2000 samples. Using the gold standard assay of culture, 500 of these samples were found to be true positives and 1500 true negatives. When tested by the new antigen assay, 450 of the true positives tested positive, and 1485 of the negative samples tested negative.
What is the specificity of this antigen assay?

A)96.75%
B)90.00%
C)99.00%
D)95.00%

Question 20

Group B Strep that an infant is exposed to in the vaginal canal can cause neonatal fatalities in 48 hours, and the current test for diagnosis can take 24-48 hours. A laboratory has developed a 6-hour antigen assay to diagnose the disease. The lab ran this test on 2000 samples. Using the gold standard assay of culture, 500 of these samples were found to be true positives and 1500 true negatives. When tested by the new antigen assay, 450 of the true positives tested positive, and 1485 of the negative samples tested negative.
What is the efficiency of the assay?

A)96.75%
B)90.00%
C)99.00%
D)95.00%

Question 21

What is the dilution of the fifth tube in a 2-fold serial dilution when the first tube's dilution is 1:10?

A)1:40
B)1:1000
C)1:160
D)1:80

Question 22

A nanometer is

A)10^-1 meters
B)10^-3 meters
C)10^-6 meters
D)10^-9 meters

Question 23

What dilution does a 1:2 dilution of a 1:0 dilution give?

A)1:5
B)1:2
C)1:10
D)1:20

Question 24

A microgram is

A)10^-1 grams
B)10^-3 grams
C)10^-6 grams
D)10^-9 grams

Question 25

A milligram is

A)10^-1 grams
B)10^-3 grams
C)10^-2 grams
D)10^-9 grams