This study will look at measuring the activity of natural killer (NK) cells using the in vitro diagnostic device NK Vue in subjects being screened for colorectal cancer using colonoscopy. The NK Vue diagnostic test for natural killer cell activity uses the principle of stimulation of whole blood with a proprietary cytokine followed by the quantitative detection of interferon gamma using an immunoassay. NK Vue is intended to be used for the monitoring of the immune status of individuals. Measurement of NK cell activity could be a useful tool for assessing changes in immunosurveillance in patients with conditions or diseases where NK cell activity has been shown to be reduced, such as colorectal cancer.

Inclusion Criteria:

• Subjects undergoing colonoscopy at the hospital
• Subjects who have adequately prepared for their colonoscopies as per their doctor's directions
• Subjects whose colonoscopy preparation has been deemed to be excellent or sufficient during the colonoscopy procedure
• Subjects who provide informed consent to participate in the trial
• Subjects >40 years of age

Exclusion Criteria:

• Lack of understanding and/or participation due to illiteracy
• History of Active viral or bacterial infection
• History of prescription use of immunosuppressive drugs within the last six months
• History of anticancer treatments including surgery or chemotherapy
• History of autoimmune disorders (rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, inflammatory bowel disease including Crohn's disease, Type I diabetes, Guillain-Barré syndrome)
• Known HIV, Hepatitis B, or Hepatitis C infection
• Currently participating (or participated within the previous 120 days) in an investigational therapeutic or device study
• Female who is pregnant, nursing, or of child-bearing potential while not practicing effective contraceptive methods.