Detection of Antibodies Against Toxoplasma gondii in Filter Paper-Dried Blood Dot Spots Compared with Serum in Pigs and Assessment of Variation Associated with Packed Cell Volume

The aim of this study was to assess the agreement between anti-Toxoplasma gondii IgG antibody detection in serum and filter paper (FP) blood spots using the indirect immunofluorescence antibody assay (IFA) and to evaluate the potential impact of the packed cell volume (PCV) on antibody detection in FPs. A pair of a serum and an FP sample was collected from 96 sows at various farms in Greece, with previously identified high seropositivity and/or risk factors associated with high seropositivity against T. gondii. The PCV value was determined using the microhematocrit method. IFA was used for the detection of antibodies against T. gondii. T. gondii-specific antibodies were detected in 45.8% serum samples and 41.6% FP samples showing almost perfect agreement. Detection in FP samples presented high sensitivity (87.1-92.8%) and excellent specificity (100%) when compared with detection in serum, regardless of the PCV values. The findings of this study support the reliability of FPs for the evaluation of the serological status of swine against T. gondii. FPs could be a good alternative sample type compared with serum for large-scale epidemiological studies.