E-nose prescreening for disease may eventually become one of the first procedures performed when a patient comes into a clinic for routine checkups and for prophylactic tests such as mammograms for breast cancer, colonoscopy for colon cancer, PAP test for certain types of human papillomavirus (HPV), prostate-specific antigen (PSA) test, and other routine prophylactic tests. Here, KLK3 is linked to breast cancer.