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 HIV-infected 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 HIV-infected patients, an accurate algorithm was not identified. Optimised access to rapid, sensitive and specific laboratory tests is essential.