Sensitivity and specificity of western blot testing of cerebrospinal fluid and serum for diagnosis of equine protozoal myeloencephalitis in horses with and without neurologic abnormalities.

This research article focuses on evaluating the effectiveness and accuracy of western blot testing (WBT) of cerebrospinal fluid (CSF) and serum in diagnosing equine protozoal myeloencephalitis (EPM), a disease affecting horses, both with and without neurological abnormalities.

Research Objective and Methodology

The primary objective of this investigation was to determine the sensitivity (ability to correctly identify positives – horses having EPM) and specificity (ability to correctly identify negatives – horses not having EPM) of western blot testing on CSF and serum. The investigation involved 65 horses with neurological abnormalities and 169 horses without neurological abnormalities. The CSF and serum from horses were examined for the presence of Sarcocystis neurona-specific antibody using the western blot testing method. The findings of the postmortem examination served as the reference against which the results of the WBT were assessed.

Results and Findings

• The sensitivity of WBT of the cerebrospinal fluid was 87% for horses with neurological abnormalities and 88% for horses without neurological abnormalities. This indicates the test’s high ability to correctly identify horses who have EPM.
• The specificity of the WBT of CSF was 44% for horses with neurological abnormalities and 60% for horses without neurological conditions. This depicts a moderate capability of the test to correctly identify horses without EPM.
• Whether horses had neurological abnormalities or not influenced neither the sensitivity nor the specificity of WBT of serum in comparison to those of WBT of CSF. In other words, the type of fluid used did not make a significant difference in the test results.
• Even in cases where horses didn’t have EPM, slight inflammation in the Central Nervous System (CNS) was found in 94 horses. This suggests that the presence of such inflammation is not a reliable indicator of a CNS infection with Sarcocystis neurona.

Conclusion

The results of the research imply that using WBT of CSF as the singular determinant for diagnosing EPM is not suitable due to it’s low specificity and subsequent increased risk of false-positive results. However, it can be used as an effective tool to exclude the potential of EPM owing to its high sensitivity. The data also underlines that there’s no advantage in testing CSF versus serum in horses without neurological abnormalities. Lastly, the common occurrence of slight CNS inflammation in both horses with or without Sarcocystis neurona-specific antibodies in the CSF suggests that this should not be considered as a definitive sign of CNS infection with Sarcocystis neurona.