Indirect fluorescent antibody testing of cerebrospinal fluid for diagnosis of equine protozoal myeloencephalitis.
OBJECTIVE
To assess the use of CSF testing with an indirect fluorescent antibody test (IFAT) for diagnosis of equine protozoal myeloencephalitis (EPM) caused by Sarcocystis neurona.


METHODS
Test results of 428 serum and 355 CSF samples from 182 naturally exposed, experimentally infected, or vaccinated horses.


METHODS
EPM was diagnosed on the basis of histologic examination of the CNS. Probability distributions were fitted to serum IFAT results in the EPM+ and EPM-horses, and correlation between serum and CSF results was modeled. Pairs of serum-CSF titers were generated by simulation, and titer-specific likelihood ratios and post-test probabilities of EPM at various pretest probability values were estimated. Post-test probabilities were compared for use of a serum-CSF test combination, a serum test only, and a CSF test only.


RESULTS
Post-test probabilities of EPM increased as IFAT serum and CSF titers increased. Post-test probability differences for use of a serum-CSF combination and a serum test only were < or = 19% in 95% of simulations. The largest increases occurred when serum titers were from 40 to 160 and pre-test probabilities were from 5% to 60%. In all simulations, the difference between pre- and post-test probabilities was greater for a CSF test only, compared with a serum test only.


CONCLUSIONS
CSF testing after a serum test has limited usefulness in the diagnosis of EPM. A CSF test alone might be used when CSF is required for other procedures. Ruling out other causes of neurologic disease reduces the necessity of additional EPM testing.
Duarte
Paulo C
PC
Animal Population Health Institute, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523-1681, USA.
Ebel
Eric D
ED
Traub-Dargatz
Josie
J
Wilson
W David
WD
Conrad
Patricia A
PA
Gardner
Ian A
IA
D000818:Animals; D000913:Antibodies, Protozoan / Q000134:cerebrospinal fluid*; D020808:Central Nervous System Protozoal Infections / Q000134:cerebrospinal fluid / Q000175:diagnosis / Q000662:veterinary*; D019084:Fluorescent Antibody Technique, Indirect / Q000662:veterinary*; D006734:Horse Diseases / Q000134:cerebrospinal fluid* / Q000175:diagnosis*; D006736:Horses; D012523:Sarcocystosis / Q000134:cerebrospinal fluid / Q000175:diagnosis / Q000662:veterinary*
D000913:Antibodies, Protozoan