Validation of the Finnish national dairy disease register--data transfer from cow health cards to the disease register.

Information on diseases of dairy cows in Finland is entered into the national disease register. Before the data from such types of secondary database are used, the quality of the data needs to be validated. In this study, 7,324 veterinary records for culled cows were compared against records in the national disease register in the period 2002 to 2008. Evaluation of the national disease register data was done by calculating completeness and correctness values. Completeness is the proportion of events that were physically recorded in the secondary database, and correctness is the proportion of correctly recorded events of all recorded events. The use of both correctness and completeness is important when describing the accuracy of secondary data. The completeness and correctness values for the Finnish national dairy disease register were 83 and 92%, respectively. We found that 39% of all unmatched diagnostic events were unreported by the artificial insemination technician who transferred the data from cow cards to the register. Logistic regression models showed that diagnostic events for cows born into the herd had twice the odds of being transferred compared with events for purchased cows. Diagnostic events for reproductive diseases had higher odds of being transferred to the register compared with all other disease groups, and the odds for transfer of the diagnostic event decreased as the age increased. We also found that if the diagnostic event was the last diagnostic event on the cow card, then its odds of being transferred to the disease register were significantly lowered. Although the Finnish national dairy disease register has good completeness and excellent correctness values, different disease groups, age groups, origin of the cow, and timing of the diagnostic event affect how well diagnostic events are transferred to the Finnish national dairy register.