Diagnostic accuracy of three commercial immunoenzymatic assays for small ruminant lentivirus infection in goats performed on individual milk samples

Evaluation of Serological Methods and a New Real-Time Nested PCR for Small Ruminant Lentiviruses

“…Therefore, it was crucial to define, based on the given serological results, an overall truth standard. We based this decision on the well-accepted concept of using a "composite standard" [13,16,[26][27][28] defined by the three screening ELISAs used. A useful complementation of this purely serological approach was the addition of a newly developed, highly sensitive PCR consisting of a primary round of a conventional PCR followed by a nested real-time PCR with the ability to differentiate between CAEV and MVV due to reliably discriminating probes with 100% specificity.…”

“…In order to evaluate the performance of each test in the absence of a generally accepted gold standard, the SRLV true positive status was identified as a composite reference standard as recommended by others [13,16,[26][27][28]. For that purpose, the composite concordance of the serological results across the different screening tests was analyzed, as shown in the Venn diagram (Figure 1).…”

“…Based on these results, we arbitrarily defined the condition of a positive reaction with at least two screening ELISAs as a composite standard rule for serological truth, complemented with real-time PCR as an additional, independent truth standard. In order to evaluate the performance of each test in the absence of a generally accepted gold standard, the SRLV true positive status was identified as a composite reference standard as recommended by others [13,16,[26][27][28]. For that purpose, the composite concordance of the serological results across the different screening tests was analyzed, as shown in the Venn diagram (Figure 1).…”

Serological, Molecular and Culture-Based Diagnosis of Lentiviral Infections in Small Ruminants

“…SRLV proviral DNA can be detected in samples of peripheral blood mononuclear cells, colostrum and milk, bronchoalveolar fluid and lungs, mammary gland, carpal synovial membranes, brain, and other secondary tissue targets such as bone marrow, spleen, lymph nodes, testicles, ovaries, uterus, heart, kidneys and liver [19,47,48,51,52,56,61,[68][69][70][71][72][73][74]. The presence of SRLV genetic material has been, also, reported in air and water samples collected from sheep farms, highlighting the potential for horizontal transmission of SRLVs [75].…”

“…In any case, for the objective assessment of its sensitivity, validation of an ELISA test should be conducted against reference sera standards with viral antigens of similar or variable strains coated on the ELISA plates. A considerable advantage of ELISAs when compared to other serological methods is the capability to be applied in various biological samples such as blood serum and plasma, and milk [ 47 , 48 , 49 , 50 , 51 , 52 , 53 ]. Among these samples, milk seems to be the most ambiguous sample matrix given that several factors may adversely affect the reliable diagnosis, such as the progressive reduction of antibodies throughout the lactation, the occurrence of false positive background signals in cases of mastitis, colostrum, increased milk fat content or even the specific immune response of the mammary gland depending on the infection stage [ 47 , 52 ].…”