Meningitis in patients with a Gram-negative direct cerebrospinal fluid examination: the value of cytochemical markers for the differential diagnosis

colleagues [1] exploring the value of cytochemical markers for the diff erential diagnosis of meningitis in patients with a Gram-negative direct cerebrospinal fl uid (CSF) examination. We have some concern as regards the confounding factors in their study. Firstly, although lumbar puncture was performed immediately on patient admission, the timepoint to obtain the CSF samples relative to the onset of disease was not uniform. For those patients with a Gram-negative direct CSF examination, the negativity may be attributed to a lumbar puncture at a very early stage. Secondly, the inclusion criteria are ambiguous. Meningitis was defi ned as a white blood cell count more than 5/mm3 in the CSF. Blood contamination due to the lumbar puncture procedure cannot be ruled out. Moreover, the white blood cell count is insuffi cient to localize infectious infl ammation to cerebral pia mater. In terms of this insuffi ciency, it is not surprising to see the low incidence of nuchal rigidity [1]. Th irdly, the lack of a gold standard for viral meningitis is a vexing problem. An imperfect standard to evaluate a diagnostic test may lead to distortions in sensitivity and/or specifi city [2,3]. In this regard, a positive group and a negative group are indispensable to determine the sensitivity and specifi city of either the serum or the CSF parameters in the diff erential diagnosis of meningitis. Aseptic menin gitis caused by intravenous immunoglobulin has not been excluded, since the causative virus was identifi ed in only 39% of the patients with viral meningitis.