Pilot Study to Identify Dentist Service Areas in Iowa

Objectives: To test a method of identifying Dentist Service Areas(DSAs). This study uses claims submitted by orthodontists for services provided to Medicaid children during a 3-year period in order to define service area boundaries for this population using methods of small area analysis of patient and provider locations.

Methods: This study reviewed all Medicaid claims from CY2008-2010 for children ages 0-21 years living in Iowa submitted by orthodontists working in private practice settings(N=9,669). The first claim submitted per child was used to identify patient origin. The patient origin and destination ZIP codes for each child were identified.  Claims were then aggregated to identify the number of children within each origin/destination ZIP code pairing. DSAs were constructed by assigning origin ZIP codes to destinations based on plurality. Plurality was determined based on where the greatest number of children per origin received care. In instances of ties between origin and multiple destinations, destination was assigned randomly. Service area boundaries were determined using ESRI ArcMap 10. Maps were generated to examine DSA distribution and characteristics.

Results: Children receiving orthodontic services during the study period had a mean age of 12.4 years at the time of service and 34% of claims were for CDT D8080(initiation of orthodontic treatment). Recipients originated from 703 ZIP codes in Iowa and were treated by orthodontists in 53 destination ZIP codes. Assigning recipient origin locations to service areas resulted in the creation of 27 crude DSAs in Iowa.

Conclusions: This pilot study was conducted to determine the feasibility of using small area analysis to identify DSAs based on Medicaid dental claims data. Using a relatively small dataset for children receiving specialists’ services successfully demonstrated the applicability of a technique that has previously been used only in association with medical claims.