Helical CT scanning may be a more sensitive screening test for lung cancer than other tests such as conventional chest films or nuclear medicine studies. The Gold Standard for lung cancer diagnosis is finding cancer cells in bronchial washings. In a study, 200 individuals were screened for lung cancer using helical CT. In this population, 40 out of 43 who screened positive for lung cancer actually had the disease based on bronchial washings while 10 of 157 screened negative for the disease by helical CT actually had the disease based on bronchial washings.

Construct a 2 X 2 table showing Screening test vs. Gold Standard. Complete the following 2 x 2 table

		Gold Standard (Bronchial Washing)
		Present	Absent	Total
Test result CT Scan	Positive	a =	b =	(a + b) =
Negative	c =	d =	(c + d ) =
	Total	(a + c) =	(b + d) =	Grand Total (a + b + c + d)

9) Calculate the sensitivity and interpret the results

1. Calculate the specificity and interpret the results
2. Calculate the positive and negative predictive value and interpret the results
3. Calculate the prevalence
4. Calculate the accuracy