The diagnostic utility of cerebrospinal fluid creatine kinase activity in the horse.

We evaluated creatine kinase (CK) activity in the cerebrospinal fluid (CSF) of 128 horses with various neurological disorders. No association was found between CSF CK activity and CSF red blood cell count, CSF nucleated cell count, CSF total protein concentration, or serum CK activity. The sensitivity and specificity of CSF CK activity as a diagnostic test for protozoal myelitis in horses (61% and 56%, respectively) was higher than for cervical stenotic myelopathy, degenerative myelopathy, or motor neuron disease, but was considered to be inadequate to be of use diagnostically. Contamination of CSF with whole blood, hemolyzed red blood cells, or serum did not substantially contribute to increases in CSF CK activity. Addition of epidural fat or dura to CSF significantly increased CSF CK activity in all cases. We suggest that the use of CSF CK activity as a diagnostic indicator of neurological disease in the horse in unreliable, and that CSF CK activity may be falsely increased by contamination of CSF with epidural fat or dura during CSF collection.