Biomarkers in cerebrospinal fluid (CSF) are crucial for diagnosing, monitoring, and prognosing neurological disorders. This study evaluates the impact of preanalytical variables, particularly container choice, on CSF protein measurements. Using 30 CSF samples, we compared sterile, additive-free tubes and lithium heparin tubes without separator gel. Protein levels were significantly elevated higher in heparin tubes (mean difference: 230.71 mg/dL, p<
0.001). This overestimation underscores the necessity of adhering to preanalytical protocols to avoid erroneous clinical interpretations and ensure accurate diagnostic outcomes.