Is it possible to differentiate tuberculous and cryptococcal meningitis in HIV-infected patients using only clinical and basic cerebrospinal fluid characteristics?

BACKGROUND: Tuberculous and cryptococcal meningitis (TBM and CM) are the most common causes of opportunistic meningitis in HIVinfected patients from resource-limited settings, and the differential diagnosis is challenging. OBJECTIVE: To compare clinical and basic cerebrospinal fluid (CSF) characteristics between TBM and CM in HIV-infected patients. METHODS: A retrospective analysis was conducted of clinical, radiological and laboratory records of 108 and 98 HIV-infected patients with culture-proven diagnosis of TBM and CM, respectively. The patients were admitted at a tertiary centre in São Paulo, Brazil. A logistic regression model was used to distinguish TBM from CM and derive a diagnostic index based on the adjusted odds ratio (OR) to differentiate these two diseases. RESULTS: In multivariate analysis, TBM was independently associated with: CSF with neutrophil predominance (odds ratio (OR) 35.81, 95% confidence interval (CI) 3.80 - 341.30, p=0.002), CSF pleocytosis (OR 9.43, 95% CI 1.30 - 68.70, p=0.027), CSF protein >1.0 g/L (OR 5.13, 95% CI 1.38 - 19.04, p=0.032) and Glasgow Coma Scale <15 (OR 3.10, 95% CI 1.03 - 9.34, p=0.044). Nausea and vomiting (OR 0.27, 95% CI 0.08 - 0.90, p=0.033) were associated with CM. Algorithm-related area under the receiver operating characteristics curve was 0.815 (95% CI 0.758 - 0.873, p<0.0001), but an accurate cut-off was not derived. CONCLUSION: Although some clinical and basic CSF characteristics appear useful in the differential diagnosis of TBM and CM in HIVinfected patients, an accurate algorithm was not identified. Optimised access to rapid, sensitive and specific laboratory tests is essential.