Reference no: EM132845409

One set of screening guidelines for the presumptive detection of colorectal cancer (CRC) in the general population recommends the use of a non-invasive screening test - Fecal Occult Blood Testing (FOBT) - as the initial screen for the disease, and, for those patients with a positive FOBT result, follow up testing with colonoscopy (CS) to presumptively confirm the diagnosis. The most commonly used FOBT in the marketplace has a published sensitivity of 50% and published specificity of 60%. Evidence regarding the efficacy of colonoscopy in detecting CRC varies by location and methodology employed, but is estimated, overall, to have a sensitivity of 95% and specificity of 90%. In the general, average CRC risk population 40 years of age and older, the prevalence of CRC is estimated to be 10%. Assuming that 100,000 average risk individuals from the general population will be screened according to these guidelines, answer the following questions:

(A) How many actual cases of CRC will FOBT identify by itself? How many actual cases will FOBT miss?

(B) What is the PPV and NPV of the FOBT?

(C) Based on FOBT results, how many patients will go on to have colonoscopy?

(D) For those patients undergoing BOTH tests (FOBT and CS), what is the overall sensitivity? How does this compare to the sensitivity of FOBT?

(E) For those patients undergoing BOTH tests (FOBT and CS), what is the overall specificity? How does this compare to the specificity of FOBT?

(F) What is the PPV and NPV of using BOTH FOBT and CS?