Question 1

The Pap test is widely used as a screen for cervical cancer risk. The properties of this test have been found to be: Sensitivity = 55.4% and Specificity = 96.8% (Mayrand et al., 2007).

If 10,000 women between the ages of 25 and 34 are screened using a Pap test to detect atypical squamous cells of undetermined significance (ASCUS),complete the expected 2x2 table below. Calculate both the false positive rate and false negative rate for this test. Note that you may end up with fractional values when calculating the number of patients in each cell - just round to the nearest whole number.

	Disease present	No disease present	Total
Positive test			1134
Negative test			8866
	1560	8440	10,000

False positive rate = ____________________

False negative rate = ____________________

Run a second sequential screen

Question 2

The Pap test has a notoriously low sensitivity. Let's now administer a second screen to only those with positive Pap test results. The patient must be identified as positive by this second screen as well in order to be diagnosed as positive. The second screen is a HPV DNA test for high risk strains of the virus. The sensitivity of the DNA test is 94.6% and the specificity is 94.1%.

Construct a 2x2 table for those 1134 who tested positive with the Pap test, and who will now undergo HPV DNA testing. Calculate both the net sensitivity and net specificity of these screens. Note that the net sensitivity is just the proportion of those with the condition that are classified as positive after both tests. Similarly, the net specificity is the proportion of those without the condition that are classified as negative after both tests. You do not need any specific formulas to calculate either value.

	Disease present	No disease present	Total
Positive test
Negative test
			1134

Net sensitivity = _________________________

Net specificity = _________________________

Question 3

Question 3: Testing the negative testers

Since the Pap test has such a low sensitivity, there are many false negatives. So rather than administering the HPV DNA test to those that tested positive on the Pap test, let's see what would happen if we instead administered this test to everyone that testednegativeon the Pap test.

Construct the 2x2 table for the 8866 patients that had a negative Pap test, and calculate both the net sensitivity and net specificity of this testing scheme.

	Disease present	No disease present	Total
Positive test
Negative test
			8866

Net sensitivity = _________________________

Net specificity = _________________________

Question 4

Given the results of the calculations, what would your recommendation be in order to best screen for cervical cancer risk among patients?