Expert elicitation of the diagnostic performance of two tests for Bacterial Kidney Disease (BKD) surveillance in Atlantic salmon (Salmo salar L.) broodstock in Chile

Abstract

The objective of this study was to obtain diagnostic performance estimates for immunofluorescence antibody test (IFAT) and quantitative polymerase chain reaction (qPCR) tests, for Bacterial Kidney Disease (BKD) surveillance in farmed Atlantic salmon (Salmo salar.) broodstock without clinical signs compatible with the disease in Chile. To obtain diagnostic sensitivity (DSe) and specificity (DSp) estimates of those tests, an expert elicitation process was conducted using the trial roulette method during a workshop with 18 national experts on BKD diagnostics and control. A questionnaire was given to the experts to gather information on their previous experience with BKD, and 12 experts who received an introduction to the expert-elicitation process and graphical representation of statistical distributions. Experts were divided into three groups and requested to draw distributions of DSe and DSp parameters using an online tool. Then figures where projected and discussed among participants. After the discussion round, experts were requested to redraw their distributions (if considered necessary). The agreement between groups was assessed by calculating the overlapping areas between the three distributions for each parameter. Finally, a consensus distribution was generated.

In general, groups had moderate to high agreement with overlapping areas between 53% to 93% for DSpIFAT, DSeqPCR, and DSpqPCR. Conversely, no agreement was reached for the DSeIFAT distribution. Specifically, median estimates of 89.5%, 90.5%, and 95.9%, were obtained for DSpIFAT, DSeqPCR, & DSpqPCR, respectively. In the case of DSeIFAT, the first group provided a median estimate of 28%, whereas groups 2 and 3 reached a consensus value of approximately 62%. This study provides information that is not available in the country, and will help to adjust current BKD control programs, which mainly rely on the use of qPCR assays.