The Link King
Record Linkage and Consolidation Software
Accuracy of Record Linkage Software in Merging Dental Administrative Datasets
(IADR/AADR/CADR 87th General Session and Exhibition (April 1-4, 2009))

H. BEIL, R.G. ROZIER, and J.S. PREISSER, University of North Carolina, Chapel Hill, NC
Copyright Camelot Consulting 2004
The Link King v5.2.4 (last bug-free version)

computer records for dental investigations and to determine the optimal cutoff point with
respect to software-generated “levels of certainty” for declaring matches.

Methods: The Link King is publicly available software that links administrative databases
using probabilistic and deterministic methods on 5 levels of certainty. It was used to link
records in North Carolina Medicaid files to public health surveillance of dental caries (SoDC)
history (dmft) for kindergarten students with no unique identifiers. The link was based on the
child's name, birth date, gender, race and county. After linking the Medicaid and SoDC files,
we randomly sampled 140 matches (N=40,032) and 20 non-matches (N=35,119). For a gold
standard, two research staff reviewed the software-generated matches (or non-matches) and
determined whether each classified linked pair was a true match. Sn and Sp were calculated
for decision rules corresponding to cutoff points at the 5 levels of certainty. The optimal
cutoff point was determined from the ratio of the Sn multiplied by the Sp of adjacent levels
and their 95% CIs. CIs for the ratio containing 1 were considered as evidence of similar
accuracy levels for adjacent cutoff points.

Results: The minimum Sn (95% CI) value was 85.4% (79.2%, 91.5%) and the minimum Sp
(95% CI) was 99.4% (98.8%, 100%). All 5 levels of matching should be included to optimize

Conclusion: Linking administrative databases allows dental researchers to conduct studies
that otherwise would not be possible. Linking data by expert review can be time consuming
and prone to errors when there are no unique identifiers. This study found that a publicly
available software program accurately merged dental claims and surveillance data. The Link
King could be useful to dental researchers in merging administrative databases.