African swine fever (ASF) is a severe disease caused by African swine fever virus (ASFV). In field settings, detection of ASFV can be achieved using pen-side tests, including lateral flow assays (LFAs) targeting virus antigens. In this study, we tested an LFA for the detection of ASFV antigens (an ASFV Ag LFA) in whole blood and serum. As a novel feature, we combined the ASFV Ag LFA with a rapid diagnostic device, the iaX reader, which generated quantitative results for the levels of ASFV antigens. Compared to qPCR, the ASFV Ag LFA in combination with the iaX reader had a diagnostic sensitivity of 100% (1.00, 95% confidence interval 0.92-1.00) and a diagnostic specificity of 91% (0.91, 95% confidence interval 0.72-0.99) for serum. For whole blood, the observed diagnostic sensitivity was lower, 79% (0.79, 95% confidence interval 0.63-0.90), while the diagnostic specificity was comparable to that reported for serum, 95% (0.95, 95% confidence interval 0.77-1.00). When comparing quantitative agreement using intraclass correlation coefficient estimates, the ASFV Ag LFA had a high level of agreement with the ASFV qPCR for serum, while a more moderate agreement was observed for whole blood. Bland–Altman and regression analyses demonstrated that agreement for both types of blood samples was not uniform and was highest when virus levels were high. In summary, the combination of the LFA and the diagnostic reader demonstrated a better performance for the detection of ASFV antigens in serum samples compared to whole blood.
Olesen et al. (Mon,) studied this question.