In Reply.
—Increased activity in cerebrospinal fluid (CSF) of creatine kinase (CK) or of its more brain-specific BB isoenzyme (CK-BB) now appears to reliably indicate brain damage after brain ischemia1,2 and head trauma3,4 and possibly also after stroke.5 Unfortunately, the clinical use of CK and CK-BB measurements has been, and to some extent still is, hampered by technical difficulties. Some of these problems have been discussed previously.6,7 Chandler and coworkers focus on two of the more important ones: the use of a reactivator and the possible presence in CSF of mitochondrial CK (CK-mt) in addition to the cytoplasmic forms.Creatine kinase is rapidly inactivated in serum and CSF but is reactivated prior to assay with the use of an SH-compound, which is a reactivator that is now included in all commercial CK reagents. We use reagents containing N-acetylcysteine (NAC) as a reactivator. Dithiothreitol (DTT) is a