Objective: To evaluate the completeness of the postcodes held in the data sets of the Dental Practice Board (DPB), and the use of the location of the dental practice at which a patient is registered, as a proxy for the location of their residential address.
Basic research design: A cross-sectional evaluation of anonymised person-based registration data held by the DPB. The study population was all children aged under 6 years registered with a dentist in the North West Region of England. The percentage of records that could be geo-referenced from the postcodes contained within the DPB's data sets was calculated. For all records which could be geo-referenced, the proportion of children who lived in the same health authority as the dental practice they were registered with was also calculated.
Main outcome measures: A total of 193,466 children in the North West Region were registered with a general dental practitioner (GDP). Of this total 117,607 (60.8 percent) could be geo-referenced from the contents of the postcode field. However, there was considerable variation in the match across the region. The majority of children lived in the same health authority as the dental practice they were registered with. It was noticeable that a greater proportion (28.5 percent) of residents registered with a dentist located within the boundaries of Manchester Health Authority were not Manchester residents.
Conclusions: Due to a significant proportion of missing postcodes, data presently held by the DPB cannot be used to calculate accurate registration rates at a small area level. Using the dental practice location as a proxy for residential address is inaccurate at health authority level, especially for large conurbations. This inaccuracy will increase at small area level. Registration data held by DPB are a potentially valuable information source, but before this information can be of use to commissioners the problem of poor postcode coverage will need to be resolved.