Validation of the Nordic disease databases

The Nordic disease databases have been in operation for several decades, but only limited efforts has been made to validate them. In 2007 a joint Nordic project was initiated with the aim to validate each national database and to compare the data validity between countries. Validation was made by “patient chart reviews” and by using a second source of data collected on-farm. The intention to treat sick cows also affects the completeness of the records, and this was evaluated by investigating attitudes of farmers and veterinarians. The results showed that the correctness of the data was high, but that completeness was less than 100% and it varied by disease complex and country. Standardization of disease registrations is necessary for valid between-country assessments, but adjustments for incompleteness can meanwhile be used. There were also differences between countries in the attitudes to treat sick cows, which also influences the comparability of disease records between countries.