In the January/February issue of the journal Public Health Reports, a group of researchers describe how they developed a computer matching technique to compare two large sets of medical records with limited intrusion into patients -- privacy.
The authors wanted to establish how many members of a health maintenance organization (HMO) in Massachusetts with active tuberculosis (TB) were listed with the state's TB registry but were not known to the HMO as having active TB.
To do this, they developed a code using the first two letters of a person's last name, the first two letters of the first name, the month of birth, the year of birth, and the person's sex. Without needing to see any individual patient listings, they applied this coding system to the HMO's entire computerized membership list and to the Massachusetts Department of Public Health's registry of TB cases. They then sorted the lists electronically, which resulted in only 124 HMO members who could have been in the TB registry without the HMO's knowledge.
An HMO staff member then read identifying information for each of the 124 people to a Department of Public Health staff person, who then reported to the HMO only a count of the number of people listed with the TB registry among the 124 people.
The authors conclude that this approach can be used in many settings to identify individuals known to different organizations while avoiding disclosure of identifying information for the vast majority of people on either list.
Journal
Public Health Reports