Normal cerebrospinal fluid protein and associated clinical characteristics in children with tuberculous meningitis

BACKGROUND: Although abnormal cerebrospinal fluid (CSF) protein can be used to predict the outcome of tuberculous meningitis (TBM) and diagnose TBM, normal CSF protein remains a concern in patients with TBM. This retrospective study aimed to assess the clinical characteristics associated with normal CSF protein, to resolve the dilemma of CSF protein in the management of childhood TBM. METHODS: Between January 2006 and December 2019, consecutive child patients (≤15 years old, a diagnosis of TBM, and tested for CSF protein) were included for analysis. CSF protein was tested on a chemistry analyzer using the pyrogallol red-molybdate method. Abnormal CSF protein was defined as >450 mg/L. Patient characteristics were collected from the electronic medical records. Then, characteristics associated with normal CSF protein were estimated in the study, using univariate and multivariate logistic regression analysis. RESULTS: A total of 125 children who met the criteria were enrolled during the study period. Twenty-nine patients had a normal CSF protein and 96 had an abnormal CSF protein. Multivariate analysis (Hosmer–Lemeshow goodness-of-fit test: χ(2)=2.486, df = 8, p = .962) revealed that vomiting (age- and sex-adjusted OR = 0.253, 95% CI: 0.091, 0.701; p = .008) and serum glucose (>5.08 mmol/L; age- and sex-adjusted OR = 0.119, 95% CI: 0.032, 0.443; p = .002) were associated with the normal CSF protein in childhood TBM. CONCLUSION: In suspected childhood TBM, patients without vomiting or having low serum glucose are easy to present with normal CSF protein. Hence, when interpreting the level of CSF protein in children with such characteristics, a careful clinical assessment is required. KEY MESSAGES: In suspected childhood tuberculous meningitis, patients without vomiting or having low serum glucose are easy to present with normal CSF protein. Hence, when interpreting the level of CSF protein in children with such characteristics, a careful clinical assessment is required.