Medical Record Linkage of Anonymous Registries without Validated Sample Linkage of the Dutch Perinatal Registries

This paper describes the linkage of data from three Dutch Perinatal Registries: the Dutch National Midwife Registry, the Dutch National Obstetrics Registry and the Dutch National Pediatrics Registry, for the year of 2001. All these registries are anonymous and lack a common identifier. We used probabilistic and deterministic record linkage techniques to combine data from the mother, delivery and child involving to the same pregnancy. Records of singleton and twin pregnancies were linked separately. We have developed a probabilistic close method based on maximum likelihood methods to estimate the weights of individual linking variables and the threshold value for the overall weight. Probabilistic linkage identified 80% more links than a full deterministic linkage approach. External validation revealed an error rate of less than 1%. Our method is a flexible and powerful method to link anonymous registries in the absence of a gold standard.