The Community Health Index is a register of all patients in NHS Scotland, Scotland's publicly funded healthcare system. The register exists to ensure that patients can be correctly identified, and that all information pertaining to a patient's health is available to providers of care.[1]
Patients are identified using a ten-digit number known as the CHI Number.[2] This number is normally formed using the patient's date of birth (as DDMMYY), followed by four digits: two digits randomly generated, the third digit identifying gender at birth (odd for men, even for women) and a check digit.[3] As of November 2009, uptake of this number varied across Scotland from 96.0% to 99.8%.[4]
The CHI number is included in electronic medical referencing systems, such as AMS (Acute Medicine Service), CMS (Chronic Medicine Service) and eMAS (Electronic Minor Ailment Scheme). All of these connect to Scotland's ePharmacy which contains details of all medical patients for Scotland.