Objective: To assess the diagnostic accuracy of two minimally invasive methods of blood collection and a reference method.

Materials and methods: Blood samples were collected from 30 pigs at 7 and 8 weeks of age. Fifteen pigs were then inoculated with porcine reproductive and respiratory syndrome virus (PRRSV) VR-2332 and 15 remained uninoculated. Pigs were sampled weekly for 7 weeks post inoculation (PI) using a reference sample (jugular vein sample) and two index samples (whole blood from the auricular vein collected either with a sterile polyester swab or using a capillary tube system). All samples were tested by quantitative reverse transcriptase-polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assay (ELISA) using established protocols. Continuous sample data for the three sampling methods were compared by analysis of the area under the receiver-operating characteristic curve.

Results: Sensitivity and specificity of qPCR testing for all samples ranged from 93% to 100% for weeks 1 through 3 PI. Results of ELISA testing depended on cutoff selection. Optimized ELISA sample:positive (S:P) ratio cutoffs for swab-sample data were significantly lower (mean S:P ratio cutoff = 0.08, SD = 0.05) than the industry standard (0.4). When the industry standard cutoff of 0.4 was utilized, swab-sample sensitivity ranged from 20.0% to 55.6% over weeks 2 through 7 PI.

Implications: Diagnosis of viremic animals using qPCR can be equivalently accomplished using any of the sampling methods. PRRS ELISA status can be determined using any of the sampling methods if an alternative S:P ratio cutoff is used.