Open Access Research article

Validation of de-identified record linkage to ascertain hospital admissions in a cohort study

Alison Beauchamp1*, Andrew M Tonkin1, Helen Kelsall1, Vijaya Sundararajan23, Dallas R English45, Lalitha Sundaresan2, Rory Wolfe1, Gavin Turrell6, Graham G Giles145 and Anna Peeters1

Author Affiliations

1 Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia

2 Victorian Data Linkages, Department of Health, Melbourne, Australia

3 Department of Medicine, Monash Medical Centre, Monash University, Melbourne, Australia

4 Cancer Epidemiology Centre, Cancer Council Victoria, Melbourne, Australia

5 Centre for Molecular, Environmental, Genetic and Analytic Epidemiology, School of Population Health, University of Melbourne, Melbourne, Australia

6 School of Public Health, Queensland University of Technology, Brisbane, Australia

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BMC Medical Research Methodology 2011, 11:42  doi:10.1186/1471-2288-11-42

Published: 8 April 2011



Cohort studies can provide valuable evidence of cause and effect relationships but are subject to loss of participants over time, limiting the validity of findings. Computerised record linkage offers a passive and ongoing method of obtaining health outcomes from existing routinely collected data sources. However, the quality of record linkage is reliant upon the availability and accuracy of common identifying variables. We sought to develop and validate a method for linking a cohort study to a state-wide hospital admissions dataset with limited availability of unique identifying variables.


A sample of 2000 participants from a cohort study (n = 41 514) was linked to a state-wide hospitalisations dataset in Victoria, Australia using the national health insurance (Medicare) number and demographic data as identifying variables. Availability of the health insurance number was limited in both datasets; therefore linkage was undertaken both with and without use of this number and agreement tested between both algorithms. Sensitivity was calculated for a sub-sample of 101 participants with a hospital admission confirmed by medical record review.


Of the 2000 study participants, 85% were found to have a record in the hospitalisations dataset when the national health insurance number and sex were used as linkage variables and 92% when demographic details only were used. When agreement between the two methods was tested the disagreement fraction was 9%, mainly due to "false positive" links when demographic details only were used. A final algorithm that used multiple combinations of identifying variables resulted in a match proportion of 87%. Sensitivity of this final linkage was 95%.


High quality record linkage of cohort data with a hospitalisations dataset that has limited identifiers can be achieved using combinations of a national health insurance number and demographic data as identifying variables.