(Reuters) - U.S. health regulators on Thursday approved a first-of-its-kind DNA test by Swiss drugmaker Roche Holding AG to help physicians track progress in treating organ transplant patients for a common virus. Roche's COBAS AmpliPrep/COBAS TaqMan CMV Test is designed for use on solid organ transplant patients undergoing cytomegalovirus (CMV) antiviral therapy. CMV is a common virus that can ...