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Comparison of two commercial ELISAs for the serological diagnosis of salmonellosis in pigs
Author(s) -
Mejía W.,
Casal J.,
Mateu E.,
Martín M.
Publication year - 2005
Publication title -
veterinary record
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.261
H-Index - 99
eISSN - 2042-7670
pISSN - 0042-4900
DOI - 10.1136/vr.157.2.47
Subject(s) - kappa , serology , veterinary medicine , receiver operating characteristic , linear correlation , zoology , mathematics , predictive value , medicine , biology , statistics , antibody , immunology , geometry
Serum samples from 361 pigs (194 fattening pigs and 167 sows) were examined by means of two commercial ELISA s (Svanovir; Svanova Biotech and Salmotype; Labor Diagnostik) used for the serological diagnosis of salmonellosis in pigs; 211 of the samples came from farms of known bacteriological status and the other 150 were collected randomly from 60 farms of unknown status. The ELISA s were done according to the manufacturers’ directions and the samples were categorised accordingly. The results were compared by using a linear regression analysis and by the calculation of Kappa values. To try to improve the agreement between the tests, the raw optical densities ( OD s) were transformed to sample/positive ( S/P ) ratios by using the positive control as a reference, and cut‐off values for these S/P ratios were calculated by means of a receiver operating characteristic ( ROC ) analysis. All but two of the known infected farms were recognised as such by both tests. However, the correlation of the raw OD s for individual pigs was poor (r=0·546) and had a Kappa value for the results categorised according to the manufacturers’ recommendations of 0·191. On some farms the correlation was high (r=0·97) but on others it was low (r=0·05) with no apparent reason for the difference. The S/P ratios did not improve the agreement (Kappa=0·25).