- The transfusion chain is susceptible to error at every step. Accurate patient registration is a key first step that links a patient with their historical medical profile, yet patient registration is marked by its own challenges. Registration errors are deviations from standard operating procedures that occur during the process of patient registration. A frequent consequence of registration errors is the obfuscation of historical information and patient misidentification. Through duplicate registrations, patient information can be spread across multiple records and through hybrid registrations information from multiple patients can be combined into a single record. Patients with the same core identifiers, and the misuse of health insurance information also pose a threat to accurate registration. In the context of transfusion, this can lead to ABO discrepancies, failing to match for previously identified alloantibodies, and redundant serological investigations. Other consequences include missed billing opportunities and the inadvertent sharing of medical information. Reducing the occurrence of registration errors can be achieved through a multifaceted approach combining targeted educational efforts with technological improvements to the registration system. A recent development being the use of biometric identifiers. Despite their frequency, published reports on the occurrence and underlying cause of registration errors are rare. Most reports are found within articles on general medical errors or misidentification events and consequently, the true rate of registration errors among health information systems is not known. Here we summarize literature pertaining to how and why registration errors occur and their implications in the context of blood transfusion.