(N19) Accuracy of Urinary Dipsticks for Glucose and Protein Determination in Cerebrospinal Fluid of Dogs

Abstract:

Background: Urinary dipsticks (UD) provide a bedside test to estimate protein and glucose concentration in cerebrospinal fluid (CSF) in humans. However, only one study suggests it as a screening test for estimating CSF proteins but not glucose in dogs.Hypothesis/

Objectives: Evaluate the precision of UD to assess proteins and glucose concentration in CSF samples of dogs with CNS disorders compared to the standard method.Animals: 22 samples of CSF from dogs with CNS diseases.

Methods: CSF proteins and glucose were measured with UD and biochemistry (pyrogallol red and glucose oxidase reaction, respectively) in each sample. Results were converted into scores to allow comparison between methods. A proportion of divergence between methods and its confidence interval were calculated using the z-test, with a significance of 0.05. The sensitivity (Se), specificity (Sp), positive (PPV) and negative predictive (NPV) values, and accuracy (Ac) of UD were determined for two cut-off levels of CSF proteins (15mg/dL and 30mg/dL) and glucose (40mg/dL and 100mg/dL).

Results: The proportion of divergence between methods for CSF proteins was 64% (CI: 44-84%) and CSF glucose was 73% (CI: 54-91%). Only eight CSF proteins and four CSF glucose had equal results for the two methods. UD had better results as a screening test when the cut-off level was 15mg/dL for proteins (Se: 78,9%; Sp: 66,7%; PPV: 93,7%; NPV: 33,3%; Ac: 77,3%) and 40mg/dL for glucose (Se: 89,5%; Sp: 33,3%; PPV: 89,5%; NPV: 33,3%; Ac: 81,8%).Conclusions and clinical importance: The urinary dipstick is unreliable to estimate CSF proteins or glucose.