USMLE Step 2 CK Lecture Notes 2017: Internal Medicine (USMLE Prep)

Book Preface

A 39-year-old woman comes to the clinic very concerned about her risk of developing cancer. Her father was diagnosed with colon cancer at age 43, and her mother was diagnosed with breast cancer at age 52. She is sexually active with multiple partners and has not seen a physician since a motor vehicle accident 15 years ago. She denies any symptoms at this time, and her physical examination is normal. She asks what is recommended for a woman her age.

Screening tests are done on seemingly healthy people to identify those at increased risk of disease. Even if a test is available, however, that does not necessarily mean it should be used to screen for a particular disease.

•    Several harmful effects may potentially result from screening tests.
•    Any adverse outcome that occurs (large bowel perforation secondary to a = colonoscopy) is iatrogenic.
•    Screening may be expensive, unpleasant, and/or inconvenient.
•    Screening may also lead to harmful treatment.

Finally, there may be a stigma associated with incorrectly labeling a patient as “sick.”

For all diseases for which screening is recommended, effective intervention must exist, and the course of events after a positive test result must be acceptable to the patient. Most important, the screening test must be valid, i.e., it must have been shown in a randomized, double-blinded trial to decrease overall mortality in the screened population. For a screening test to be recommended for regular use, it has to be extensively studied to ensure that all of the above requirements are met.  The 3 malignancies for which regular screening is recommended are cancers of the colon, breast, and cervix.