Once is enough. An enterprise-wide master patient index can eliminate duplicate entries and overlays with unique patient identifiers.
Baldwin
F D
FD
D019033:Delivery of Health Care, Integrated; D006801:Humans; D008500:Medical Records Department, Hospital; D016347:Medical Records Systems, Computerized / Q000145:classification*; D009096:Multi-Institutional Systems; D010355:Patient Identification Systems; D012984:Software; D018511:Systems Integration; D014481:United States