Diagnostic accuracy of urine test strips for CSF analysis: high sensitivity in detecting blood, low sensitivity but high specificity in detecting inflammation

Background Rapid cerebrospinal fluid (CSF) analysis is crucial for diagnosing and treating time-critical neurological diseases. However, thorough laboratory diagnostics are time-intensive or often unavailable in resource-limited settings. Urine test strips (UTS) may provide a simple bedside alternative, but evidence remains limited and largely restricted to single manufacturers. This study evaluated the diagnostic performance of UTS for CSF analysis and compared different manufacturers. Methods In this prospective study, 285 CSF samples from patients with different neurological diseases were analyzed using UTS from five manufacturers. Strip results for leukocytes, erythrocytes, protein, and glucose were compared across manufacturers and against laboratory measurements. Diagnostic accuracy for detecting blood in CSF, pleocytosis, and for differentiating infectious from non-infectious conditions was assessed. Results For erythrocyte detection, the UTS showed high sensitivity (86–95%) and negative predictive value (NPV, 92–97%). In contrast, for CSF pleocytosis, specificity and positive predictive value (PPV) were high (100%), whereas sensitivity was low (11%). UTS underestimated low leukocyte counts and showed variable performance for protein detection. For differentiating infectious from non-infectious conditions, leukocytes and glucose demonstrated high specificity and PPV. Combining parameters (≥ 2/3 positive: leukocytes, protein, glucose) yielded consistently high specificity (98%) and PPV (80–85%), but low sensitivity (13–15%) and NPV (63%). No relevant differences between manufacturers were observed. Conclusion UTS provide a rapid, low-cost bedside tool for initial CSF assessment, with particular strength in reliably excluding blood contamination. In contrast, their utility for detecting inflammatory or infectious conditions is limited due to low sensitivity. Therefore, while UTS may support early bedside decision-making, they cannot replace standard laboratory diagnostics.