WASHINGTON (AP) — U.S. health regulators on Monday approved a first-of-its-kind blood test for colon cancer, offering a new way of screening for a leading cause of cancer deaths.Test manufacturer Guardant said the Food and Drug Administration approved its Shield test for screening in adults 45 and older who have an average risk of colon cancer. The test isn’t a replacement for colonoscopies, but provides a noninvasive approach to screening.Doctors can already order Shield for patients as a labor...