A simple statistical approach for assessing inter-laboratory comparison tests for classical swine fever diagnosis

The aim of this study was to compare on an objective basis the results obtained during five classical swine fever (CSF) ring tests conducted in Germany between 1999 and 2003. A novel and simple statistical approach used in behavioural sciences was used. For each ring test, the regional laboratories received a panel of five lyophilized pig sera. The panel contained CSF virus positive and negative samples. The final task of the laboratory was to ascertain if a serum sample was positive for CSF or not. Some sera were very easy to diagnose as CSF positive while some sera had border line values and proved to be challenging. Depending on the degree of difficulty the sera were divided into five categories. The evaluation of the ring test results was performed using a scoring system based on a score from -3 to +3 which takes into consideration the degree of difficulty to produce a correct diagnosis. To compare the results between different laboratories and/or between different ring tests more easily the total score of one laboratory was expressed in percentage. The final analysis of the data showed that the CSF diagnostic quality improved continuously.