![]() A recent paper about EPM like disease in sea otters (Wendte et al. Although a wide range of serum titers was observed for necropsy positive EPM cases, there was a trend for higher serum titers (≥ 1:4000) to correlate better with EPM. A <100 ratio has a sensitivity = 83% and a specificity = 97%. As intrathecal IgG production increases, the titer ratio decreases and ratios of <100 strongly correlate with EPM. While individual serum and CSF titers can be determined, the ratio of serum:CSF titers is very predictive of an EPM diagnosis. They were validated with paired sera and CSFs from 66 necropsy (neurologic) cases and ~200 well characterized field cases (presented at 2010 ACVIM, manuscript in preparation). 2011) are the basis of the newest EPM test. The surface antigens 2, 3 and 4 (Howe et al. neurona isolates lack the SAG1 gene and will test as false negative. It is now well documented that a number of S. neurona was used for both the SAG1 ELISA test development and experimental infection. A serum titer of 1:32 is said to be clinically significant. Based on this limited set, the sensitivities were reported on marketing material as 94% (serum) and 100% (CSF) and specificities as 86% (serum) and 94% (CSF). 2003) was validated (serum and CSF) using 6 experimentally infected horses. The immunodominant surface antigen designated 1 (SAG1) ELISA (Ellison et al. Depending on the antigen used, the actual titer values and their significance vary. The procedures and validation of WB performed at several academic labs (UC Davis, Auburn and Oregon State) have not been publically presented or published.Įnzyme linked immunosorbent assay (ELISA) is a simple, quantitative method which generates titers. The specificity would be expected to be much lower if normal horses from EPM endemic regions were used as negative EPM cases. Using these two different standards, the sensitivity and specificity were reported as 100% and 98%, respectively. This test was validated using sera from 57 horses native to India and Germany, where EPM does not exist (true negatives) and 6 EPM necropsy positive cases (true positives). This species infects cattle but not horses. 2000) includes a step using bovine sera with a high titer of Sarcocystis cruzi IgG under the premise of eliminating cross reactivities and increasing specificity. Respectively, serum and CSF sensitivities were 90% and 83% and the specificities were 42% and 86%. The most current calculation of test performance was performed by Equine Diagnostic Solutions (EDS) using 66 necropsied neurologic horses with 30 diagnosed as EPM. Paired serum and CSF samples are recommended. 1993) was well validated with several hundred necropsied neurologic cases as the gold standard. The original standard WB (Granstrom et al. This method is more sensitive to blood contamination in CSF samples, which could cause false positive results. The presence of specific immunoreactive bands is the basis for the subjective interpretation of results. Western blot (WB) is a complex, semi-quantitative method requiring much expertise. Repeat side-by-side testing with any quantitative test format can be useful in noting changes in the level of IgG with time, either due to natural response or in response to treatment.Īll detect the IgG response to the causative parasite.Īre distinguishable by the strain of parasite used as antigen source, assay format, validation samples, recommended diagnostic sample and result interpretation. Testing of non-neurologic horses is generally not recommended. The reluctance to perform a spinal tap due to risk, cost or inexperience is understandable and although not the preferred approach, a positive serum IgG test in the presence of neurologic signs and history compatible with EPM, supports a diagnosis of EPM.Īlthough response to treatment is often used as a diagnostic test, there are many false results that would have been predicted by prior serum and CSF testing. Testing of cerebrospinal fluid (CSF), with a paired serum, is more predictive of active disease than serum alone. The standard of practice for diagnosis is to perform a complete neurological exam, accompanied by laboratory tests that detect an immunological response to infection. It is most commonly caused by the parasite Sarcocystis neurona and more rarely by Neospora hughesi. EPM is a neurological disease of the Americas.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |