Interferon γ quantification in cerebrospinal fluid compared with PCR for the diagnosis of tuberculous meningitis
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- Juan, R.S., Sánchez-Suárez, C., Rebollo, M.J. et al. J Neurol (2006) 253: 1323. doi:10.1007/s00415-006-0215-y
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To assess the utility of interferon γ (INF-γ) levels in cerebrospinal fluid (CSF), for the diagnosis of tuberculous meningitis (TBM), and compare these results with aPCR technique.
We studied CSF samples from patients with proven or probable TBM and a control group, composed by patients with other causes of meningitis and without meningitis. INFγ levels were measured by radioimmunoassay. A PCR technique was performed using IS6110 primers.
Of the 127 patients studied, 20 (15.6%) had TBM, 59 (46%) had meningitis of another aetiology and 49 (38.4%) had were HIV and non-HIV patients with normal CSF. The area below the ROC curve for interferon γ levels in the diagnosis of TBM was 0.94. A cut-off of 6.4 IU/mL yielded a sensitivity of 70% and a specificity of 94%. False positive results were observed in 7 of the 59 patients (11.8%) with non-TB meningitis, (patients with herpetic meningoencephalitis and meningitis due to intracellular microorganisms). INF-γ sensitivity was higher than PCR (70% vs. 65%). Both tests performed together showed higher sensitivity (80%) and specificity (92.6%).
CSF INF-γ levels (> 6.4 IU/mL) are very valuable in TBM diagnosis. PCR and INF-γ could be simultaneously used to increase the diagnostic yield.