Quality management in reference tests for the diagnosis of classical swine fever

Pestivirus control programs: how far have we come and where are we going?

Classical swine fever (CSF) is endemic in large parts of the world and it is a major threat to the pig industry in general. Vaccination and stamping out have been the most successful tools for the control and elimination of the disease. The systematic use of modified live vaccines (MLV), which are very efficacious and safe, has often preceded the elimination of CSF from regions or countries. Oral vaccination using MLV is a powerful tool for the elimination of CSF from wild boar populations. Bovine virus diarrhea (BVD) is endemic in bovine populations worldwide and programs for its control are only slowly gaining ground. With two genotypes BVD virus (BVDV) is genetically more diverse than CSF virus (CSFV). BVDV crosses the placenta of pregnant cattle resulting in the birth of persistently infected (PI) calves. PI animals shed enormous amounts of virus for the rest of their lives and they are the reservoir for the spread of BVDV in cattle populations. They are the main reason for the failure of conventional control strategies based on vaccination only. In Europe two different approaches for the successful control of BVD are being used: Elimination of PI animals without or with the optional use of vaccines, respectively.

Evaluation of external quality assessment results for HIV testing laboratories in Korea using current analytical methods

BACKGROUND

This report presents HIV External Quality Assessment (EQAS) results by the KCDC from the 17 HIV testing laboratories that also performed HIV-1 western blot testing of the 585 laboratories.

METHOD

The HIV EQAS panel consisted of 10 undiluted plasma samples from donors who were 3 positive, four indeterminate and 3 negative for HIV antibody. The results were analyzed by traditional methods (mean±2 SD), robust statistics (median), and Youden plots (99% coverage).

RESULTS

The sensitivities for the HIV antigen and antibody ELISAs were 94.1% and 98.3%, respectively, with the inconsistent 1.7% caused by indeterminate, weakly positive samples. The specificities of HIV antigen and antibody ELISAs were 93.3% and 100%, respectively. The traditional method detected 2 laboratories as outliers for HIV antigen testing and 3 laboratories as outliers for HIV antibody testing. The robust statistics method showed better discrimination of outliers, detecting seven laboratories as outliers for HIV antigen testing and six for HIV antibody testing. The outliers detected by the Youden plot were differentiated as six systematic and 2 random errors.

CONCLUSION

Therefore, the design of reliable EQAS based on HIV panels with varied and specified titers is prerequisites for quality improvement of HIV testing laboratories.

Virulence of classical swine fever virus isolates from Europe and other areas during 1996 until 2007

Classical Swine Fever (CSF) has caused several outbreaks in EU Member States with grave economic consequences. Several times the diagnosis of CSF was made too late partially due to non-specific clinical signs which did not raise suspicion for CSF. Virulence of CSF virus isolates (CSFV) still remains a subject of discussion and speculation as sufficient knowledge is still not available. Six uncharacterised CSFV isolates from 1996 to 2007 were assessed in animal experiments for their clinical virulence in order to broaden the knowledge about circulating CSFV and thereby assist disease eradication. A clinical (CS) and pathological score was applied and further extended by additional parameters to a modified CS (mCS) including case fatality, antibody production and leukocyte count. The unknown CSFV isolates could be classified as moderately or highly virulent. The inclusion of additional parameters, especially case fatality, into the mCS gave a more reliable classification of virulence, proving that there are clinical signs and laboratory parameters of blood which can be recognised. Therefore a subclinical course of infection is unlikely, especially in weaner pigs.

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.