PubMed · 3740692
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1986. The spinal tap.. https://doi.org/10.7326/0003-4819-105-3-464_1
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BACKGROUND: Detection of malignant cells on cytologic examination of the cerebrospinal fluid (CSF) is the diagnostic gold standard for leptomeningeal carcinomatosis. The absence of cells is a primary endpoint for most therapeutic trials. Unfortunately, false-negative results are common. Practical strategies are necessary to remedy this problem. METHODS: Four physician-dependent variables (CSF sample volume, site of CSF sampling, processing time, and frequency of CSF sampling) were identified, and their contributions to the false-negative rate of CSF cytology were evaluated prospectively in 39 patients with leptomeningeal carcinomatosis. Retrospective data were analyzed to estimate the importance of these variables in daily practice. RESULTS: False-negative CSF cytology results correlated with small CSF volume (P < 0.001), delayed processing (P < 0.001), not obtaining CSF from a site of symptomatic or radiographically demonstrated disease (P = 0.02), and sampling fewer than two times (P < 0.001). In 1 year, 97% of CSF specimens at the study institution were of inadequate volume; >25% were processed too slowly. CONCLUSIONS: False-negative CSF cytology results are common, but can be minimized by: 1) withdrawing at least 10.5 mL of CSF for cytologic analysis; 2) processing the CSF specimen immediately; 3) obtaining CSF from a site of known leptomeningeal disease; and 4) repeating this procedure once if the initial cytology is negative.
The prognosis of tuberculous meningitis (TBM) depends on early therapy based on rapid diagnosis. To study the clinical value of PCR in diagnosis of TBM, we investigated CSF specimens from 49 patients. After cell lysis and DNA preparation following a standard protocol, we performed a half-nested PCR with primers able to detect mycobacterial DNA. PCR results were evaluated according to clinical features, histopathological data, and bacteriological results. PCR detected four of five cases of confirmed TBM, corresponding to a sensitivity of 80%. Positive PCRs were also obtained in 25% CSF samples of non-TBM patients. Most of these false positive results were due to amplification of Mycobacteria fortuitum (M. fortuitum) as determined by direct sequencing analysis. To enhance specificity of our half nested protocol, the oligonucleotide primers that were specific for several mycobacterial subspecies were substituted by a primerpair, which allows selective amplification of DNA from Mycobacteria tuberculosis (M. tuberculosis). By using the altered PCR protocol, the screening of CSF samples revealed a much higher specificity (97%) and constant sensitivity (80%) in diagnosis of TBM. These findings indicate, that M. fortuitum, as an ubiquitous mycobacterial subtype of low pathogenicity, can potentially contaminate clinical specimens and account for false positive PCR results. Therefore, the clinical value of PCR in diagnosis of TBM strongly depends on appropriate oligonucleotide primers, that allow to differentiate between mycobacterial subtypes.
Herpes simplex virus type 2 (HSV-2) is more often sexually transmitted and associated with genital recurrent infection. However, HSV-2 neurological manifestations such as meningitis were already reported. We describe a case of meningitis due to HSV-2, preceded by signs suggesting a common cystitis, in a woman with no history of primary or recurrent genital infection. Six months later genital herpetic lesions occurred. One HSV-2 strain was obtained from cerebrospinal fluid (CSF) and another from genital lesions. The molecular comparative analysis using restriction endonuclease digestion patterns showed the similarity of the two strains. Our report illustrates that HSV-2 infections are underdiagnosed and that molecular techniques can be of value in clarifying the physiopathology of HSV diseases.